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[PATCH v2] perf unwind-libdw: fix a cross-arch unwinding bug

Shimin Guo via B4 Relay posted 1 patch 1 month ago
There is a newer version of this series
tools/perf/arch/arm/util/Build                     |  1 -
tools/perf/arch/arm64/util/Build                   |  1 -
tools/perf/arch/csky/util/Build                    |  2 -
tools/perf/arch/powerpc/util/Build                 |  1 -
tools/perf/arch/riscv/util/Build                   |  1 -
tools/perf/arch/s390/util/Build                    |  2 -
tools/perf/arch/x86/util/Build                     |  1 -
tools/perf/util/Build                              |  1 +
tools/perf/util/unwind-libdw-arch/Build            |  8 ++++
.../unwind-libdw-arch/unwind-libdw-arm.c}          | 10 ++---
.../unwind-libdw-arch/unwind-libdw-arm64.c}        | 10 ++---
.../unwind-libdw-arch/unwind-libdw-csky.c}         |  6 +--
.../unwind-libdw-arch/unwind-libdw-loongarch.c}    |  4 +-
.../unwind-libdw-arch/unwind-libdw-powerpc.c}      | 10 ++---
.../unwind-libdw-arch/unwind-libdw-riscv.c}        |  4 +-
.../unwind-libdw-arch/unwind-libdw-s390.c}         |  6 +--
.../unwind-libdw-arch/unwind-libdw-x86.c}          |  8 ++--
tools/perf/util/unwind-libdw.c                     | 51 +++++++++++++++++++---
tools/perf/util/unwind-libdw.h                     | 10 ++++-
19 files changed, 92 insertions(+), 45 deletions(-)
[PATCH v2] perf unwind-libdw: fix a cross-arch unwinding bug
Posted by Shimin Guo via B4 Relay 1 month ago 
From: Shimin Guo <shimin.guo@skydio.com>

The set_initial_registers field of Dwfl_Thread_Callbacks needs to be set
according to the arch of the stack samples being analyzed, not the arch
that perf itself is built for. Currently perf fails to unwind stack samples
collected from archs different from that of the host perf is running on.
This patch moves the arch-specific implementations of set_initial_registers
from tools/perf/arch to tools/perf/utli/unwind-libdw-arch, similar to the
way the perf-regs-arch folder contains arch-specific functions related to
registers, and chooses the implementation based on the arch of the data
being processed.

Signed-off-by: Shimin Guo <shimin.guo@skydio.com>
---
Changes in v2:
- Fixed the include path for perf_regs.h in unwind-libdw-x86.c
- Removed one level of "../" from the include paths in the moved files
now that they are two directory levels under tools/perf instead of three.
- Link to v1: https://lore.kernel.org/r/20251223-cross-arch-unwind-v1-1-4d71ee7db512@skydio.com
---
 tools/perf/arch/arm/util/Build                     |  1 -
 tools/perf/arch/arm64/util/Build                   |  1 -
 tools/perf/arch/csky/util/Build                    |  2 -
 tools/perf/arch/powerpc/util/Build                 |  1 -
 tools/perf/arch/riscv/util/Build                   |  1 -
 tools/perf/arch/s390/util/Build                    |  2 -
 tools/perf/arch/x86/util/Build                     |  1 -
 tools/perf/util/Build                              |  1 +
 tools/perf/util/unwind-libdw-arch/Build            |  8 ++++
 .../unwind-libdw-arch/unwind-libdw-arm.c}          | 10 ++---
 .../unwind-libdw-arch/unwind-libdw-arm64.c}        | 10 ++---
 .../unwind-libdw-arch/unwind-libdw-csky.c}         |  6 +--
 .../unwind-libdw-arch/unwind-libdw-loongarch.c}    |  4 +-
 .../unwind-libdw-arch/unwind-libdw-powerpc.c}      | 10 ++---
 .../unwind-libdw-arch/unwind-libdw-riscv.c}        |  4 +-
 .../unwind-libdw-arch/unwind-libdw-s390.c}         |  6 +--
 .../unwind-libdw-arch/unwind-libdw-x86.c}          |  8 ++--
 tools/perf/util/unwind-libdw.c                     | 51 +++++++++++++++++++---
 tools/perf/util/unwind-libdw.h                     | 10 ++++-
 19 files changed, 92 insertions(+), 45 deletions(-)

diff --git a/tools/perf/arch/arm/util/Build b/tools/perf/arch/arm/util/Build
index fd695e1fdaee2ccc300a206131b8b38a763b00ce..3291f893b943df0722dff583523fff4ae79919bc 100644
--- a/tools/perf/arch/arm/util/Build
+++ b/tools/perf/arch/arm/util/Build
@@ -1,6 +1,5 @@
 perf-util-y += perf_regs.o
 
 perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind.o
-perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
 
 perf-util-y += pmu.o auxtrace.o cs-etm.o
diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build
index d63881081d2eb1e9a83eabf82104d75308f7fc79..0177af19cc00038d6a6005592ddc530bf7eb1557 100644
--- a/tools/perf/arch/arm64/util/Build
+++ b/tools/perf/arch/arm64/util/Build
@@ -1,4 +1,3 @@
-perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
 perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
 perf-util-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o
 perf-util-y += ../../arm/util/auxtrace.o
diff --git a/tools/perf/arch/csky/util/Build b/tools/perf/arch/csky/util/Build
index 5e6ea82c42021d3d5651ca4c4a3a6e5138574e4e..6b2d0e021b11464e46d6b53974260d32ea969732 100644
--- a/tools/perf/arch/csky/util/Build
+++ b/tools/perf/arch/csky/util/Build
@@ -1,3 +1 @@
 perf-util-y += perf_regs.o
-
-perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
diff --git a/tools/perf/arch/powerpc/util/Build b/tools/perf/arch/powerpc/util/Build
index 3d0d5427aef7f26a8c05c883cc7ad763f08cbb30..5fd28ec713a4db74ecd1d26866a65ddb20e94bd3 100644
--- a/tools/perf/arch/powerpc/util/Build
+++ b/tools/perf/arch/powerpc/util/Build
@@ -9,5 +9,4 @@ perf-util-y += evsel.o
 perf-util-$(CONFIG_LIBDW) += skip-callchain-idx.o
 
 perf-util-$(CONFIG_LIBUNWIND) += unwind-libunwind.o
-perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
 perf-util-y += auxtrace.o
diff --git a/tools/perf/arch/riscv/util/Build b/tools/perf/arch/riscv/util/Build
index 58a672246024dd0f72e767d11e9958bd9913ec3c..628b9ebd418bde8cdf1ab1332bf79f7c9d50760e 100644
--- a/tools/perf/arch/riscv/util/Build
+++ b/tools/perf/arch/riscv/util/Build
@@ -2,4 +2,3 @@ perf-util-y += perf_regs.o
 perf-util-y += header.o
 
 perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
-perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
index c64eb18dbdae93adafabf8542e4c9a763ecfe057..5391d26fedd46b7d30a1bef0bff2ec2d58ec30ed 100644
--- a/tools/perf/arch/s390/util/Build
+++ b/tools/perf/arch/s390/util/Build
@@ -2,8 +2,6 @@ perf-util-y += header.o
 perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
 perf-util-y += perf_regs.o
 
-perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
-
 perf-util-y += machine.o
 perf-util-y += pmu.o
 
diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
index c0dc5965f3624a6f02525a04d287dff755356d20..fad256252bb95a8f8350b6bb1a54e8074eaebbec 100644
--- a/tools/perf/arch/x86/util/Build
+++ b/tools/perf/arch/x86/util/Build
@@ -12,7 +12,6 @@ perf-util-y += evsel.o
 perf-util-y += iostat.o
 
 perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind.o
-perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
 
 perf-util-y += auxtrace.o
 perf-util-y += archinsn.o
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 1c2a43e1dc68e7f751ec6082352b10de9ffeea62..15f8a4f4b24a46b6300e824f672dd9c0d5b7865f 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -226,6 +226,7 @@ perf-util-$(CONFIG_LIBDW) += debuginfo.o
 perf-util-$(CONFIG_LIBDW) += annotate-data.o
 
 perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arch/
 perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind-local.o
 perf-util-$(CONFIG_LIBUNWIND)          += unwind-libunwind.o
 perf-util-$(CONFIG_LIBUNWIND_X86)      += libunwind/x86_32.o
diff --git a/tools/perf/util/unwind-libdw-arch/Build b/tools/perf/util/unwind-libdw-arch/Build
new file mode 100644
index 0000000000000000000000000000000000000000..e016d54ae2a40ecba47156c8f09cb72156105727
--- /dev/null
+++ b/tools/perf/util/unwind-libdw-arch/Build
@@ -0,0 +1,8 @@
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-x86.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arm.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arm64.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-csky.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-loongarch.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-powerpc.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-riscv.o
+perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-s390.o
\ No newline at end of file
diff --git a/tools/perf/arch/arm/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
similarity index 78%
rename from tools/perf/arch/arm/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
index fbb643f224ec4b27ce9d67051fe0bc4ad555b05e..3c7f91a1af7416f57b0e4fa0dcd15a530cb44f8a 100644
--- a/tools/perf/arch/arm/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
@@ -1,11 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <elfutils/libdwfl.h>
-#include "perf_regs.h"
-#include "../../../util/unwind-libdw.h"
-#include "../../../util/perf_regs.h"
-#include "../../../util/sample.h"
+#include "../../../arch/arm/include/uapi/asm/perf_regs.h"
+#include "../../util/unwind-libdw.h"
+#include "../../util/perf_regs.h"
+#include "../../util/sample.h"
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_arm(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/arch/arm64/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
similarity index 86%
rename from tools/perf/arch/arm64/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
index b89b0a7e5ad919fed23643d219fbdc3d84deff1e..a237af99d1f87a72b99d5ed2ff965d4ef2f75434 100644
--- a/tools/perf/arch/arm64/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
@@ -1,11 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <elfutils/libdwfl.h>
-#include "perf_regs.h"
-#include "../../../util/unwind-libdw.h"
-#include "../../../util/perf_regs.h"
-#include "../../../util/sample.h"
+#include "../../../arch/arm64/include/uapi/asm/perf_regs.h"
+#include "../../util/unwind-libdw.h"
+#include "../../util/perf_regs.h"
+#include "../../util/sample.h"
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_arm64(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/arch/csky/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
similarity index 92%
rename from tools/perf/arch/csky/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
index b20b1569783d7e982e91b1b40120d29ccf2f01d1..889d3b788931f3af55b03ef8b91d5def364972e5 100644
--- a/tools/perf/arch/csky/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
@@ -2,12 +2,12 @@
 // Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd.
 
 #include <elfutils/libdwfl.h>
-#include "perf_regs.h"
+#include "../../../arch/csky/include/uapi/asm/perf_regs.h"
 #include "../../util/unwind-libdw.h"
 #include "../../util/perf_regs.h"
-#include "../../util/event.h"
+#include "../../util/sample.h"
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_csky(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/arch/loongarch/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
similarity index 91%
rename from tools/perf/arch/loongarch/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
index 60b1144bedd5f325e1512eeab05c29a1e8de2b03..1c5753ace6f63be771aa92365d3174ad8ed3a6fd 100644
--- a/tools/perf/arch/loongarch/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
@@ -2,12 +2,12 @@
 /* Copyright (C) 2020-2023 Loongson Technology Corporation Limited */
 
 #include <elfutils/libdwfl.h>
-#include "perf_regs.h"
+#include "../../../arch/loongarch/include/uapi/asm/perf_regs.h"
 #include "../../util/unwind-libdw.h"
 #include "../../util/perf_regs.h"
 #include "../../util/sample.h"
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_loongarch(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/arch/powerpc/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
similarity index 88%
rename from tools/perf/arch/powerpc/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
index 82d0c28ae3459ecdb0039cac1f534420d142739b..d5012f20a87e30809b8b44ee20572fab8668b7dd 100644
--- a/tools/perf/arch/powerpc/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
@@ -1,10 +1,10 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <elfutils/libdwfl.h>
 #include <linux/kernel.h>
-#include "perf_regs.h"
-#include "../../../util/unwind-libdw.h"
-#include "../../../util/perf_regs.h"
-#include "../../../util/sample.h"
+#include "../../../arch/powerpc/include/uapi/asm/perf_regs.h"
+#include "../../util/unwind-libdw.h"
+#include "../../util/perf_regs.h"
+#include "../../util/sample.h"
 
 /* See backends/ppc_initreg.c and backends/ppc_regs.c in elfutils.  */
 static const int special_regs[3][2] = {
@@ -13,7 +13,7 @@ static const int special_regs[3][2] = {
 	{ 109, PERF_REG_POWERPC_CTR },
 };
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_powerpc(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/arch/riscv/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
similarity index 92%
rename from tools/perf/arch/riscv/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
index dc1476e16321736de897ad53a00fbc813bd706db..2a5442b3b5bdc27252378de0073deb8a620f8779 100644
--- a/tools/perf/arch/riscv/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
@@ -2,12 +2,12 @@
 /* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
 
 #include <elfutils/libdwfl.h>
-#include "perf_regs.h"
+#include "../../../arch/riscv/include/uapi/asm/perf_regs.h"
 #include "../../util/unwind-libdw.h"
 #include "../../util/perf_regs.h"
 #include "../../util/sample.h"
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_riscv(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/arch/s390/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
similarity index 89%
rename from tools/perf/arch/s390/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
index c27c7a0d1076c890c35ba19543932c4ed5ac9c2a..18d44074a55bc1c7fa2d7150afc1f1a93d4eadf8 100644
--- a/tools/perf/arch/s390/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
@@ -4,11 +4,11 @@
 #include "../../util/perf_regs.h"
 #include "../../util/event.h"
 #include "../../util/sample.h"
-#include "dwarf-regs-table.h"
-#include "perf_regs.h"
+#include "../../arch/s390/include/dwarf-regs-table.h"
+#include "../../../arch/s390/include/uapi/asm/perf_regs.h"
 
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_s390(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/arch/x86/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
similarity index 86%
rename from tools/perf/arch/x86/util/unwind-libdw.c
rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
index 798493e887d7308cb293e29e4ba11054d0fda722..6619c60728ef6ad1e725cd86c7bcbf06b8aad28d 100644
--- a/tools/perf/arch/x86/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
@@ -1,11 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <elfutils/libdwfl.h>
-#include "perf_regs.h"
-#include "../../../util/unwind-libdw.h"
-#include "../../../util/perf_regs.h"
+#include "../../../arch/x86/include/uapi/asm/perf_regs.h"
+#include "../../util/unwind-libdw.h"
+#include "../../util/perf_regs.h"
 #include "util/sample.h"
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
+bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg)
 {
 	struct unwind_info *ui = arg;
 	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
index ae70fb56a05729b9f06a411d162eabebbf29ac52..f32694ff4ea52d4bf80a38405341864e7ff5e6c8 100644
--- a/tools/perf/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw.c
@@ -225,11 +225,45 @@ static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *
 	return true;
 }
 
-static const Dwfl_Thread_Callbacks callbacks = {
-	.next_thread		= next_thread,
-	.memory_read		= memory_read,
-	.set_initial_registers	= libdw__arch_set_initial_registers,
-};
+#define DEFINE_DWFL_THREAD_CALLBACKS(arch)                           \
+static const Dwfl_Thread_Callbacks callbacks_##arch = {              \
+	.next_thread           = next_thread,                        \
+	.memory_read           = memory_read,                        \
+	.set_initial_registers = libdw_set_initial_registers_##arch, \
+}
+
+DEFINE_DWFL_THREAD_CALLBACKS(x86);
+DEFINE_DWFL_THREAD_CALLBACKS(arm);
+DEFINE_DWFL_THREAD_CALLBACKS(arm64);
+DEFINE_DWFL_THREAD_CALLBACKS(csky);
+DEFINE_DWFL_THREAD_CALLBACKS(loongarch);
+DEFINE_DWFL_THREAD_CALLBACKS(powerpc);
+DEFINE_DWFL_THREAD_CALLBACKS(riscv);
+DEFINE_DWFL_THREAD_CALLBACKS(s390);
+
+static const Dwfl_Thread_Callbacks *get_thread_callbacks(const char *arch)
+{
+	if (!strcmp(arch, "arm"))
+		return &callbacks_arm;
+	else if (!strcmp(arch, "arm64"))
+		return &callbacks_arm64;
+	else if (!strcmp(arch, "csky"))
+		return &callbacks_csky;
+	else if (!strcmp(arch, "loongarch"))
+		return &callbacks_loongarch;
+	else if (!strcmp(arch, "powerpc"))
+		return &callbacks_powerpc;
+	else if (!strcmp(arch, "riscv"))
+		return &callbacks_riscv;
+	else if (!strcmp(arch, "s390"))
+		return &callbacks_s390;
+	else if (!strcmp(arch, "x86"))
+		return &callbacks_x86;
+
+	pr_err("Fail to get thread callbacks for arch %s, returns NULL\n",
+	       arch);
+	return NULL;
+}
 
 static int
 frame_callback(Dwfl_Frame *state, void *arg)
@@ -278,6 +312,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 	const char *arch = perf_env__arch(ui_buf.machine->env);
 	Dwarf_Word ip;
 	int err = -EINVAL, i;
+	const Dwfl_Thread_Callbacks *callbacks;
 
 	if (!data->user_regs || !data->user_regs->regs)
 		return -EINVAL;
@@ -300,7 +335,11 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 	if (err)
 		goto out;
 
-	err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui);
+	callbacks = get_thread_callbacks(arch);
+	if (!callbacks)
+		goto out;
+
+	err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), callbacks, ui);
 	if (err)
 		goto out;
 
diff --git a/tools/perf/util/unwind-libdw.h b/tools/perf/util/unwind-libdw.h
index 8c88bc4f2304b59561ffd482469ca63ce0f531f0..574b29848cce31e6bfd93021f752b518cebf73b7 100644
--- a/tools/perf/util/unwind-libdw.h
+++ b/tools/perf/util/unwind-libdw.h
@@ -9,7 +9,15 @@ struct machine;
 struct perf_sample;
 struct thread;
 
-bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_arm(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_arm64(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_csky(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_loongarch(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_mips(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_powerpc(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_riscv(Dwfl_Thread *thread, void *arg);
+bool libdw_set_initial_registers_s390(Dwfl_Thread *thread, void *arg);
 
 struct unwind_info {
 	Dwfl			*dwfl;

---
base-commit: cbd41c6d4c26c161a2b0e70ad411d3885ff13507
change-id: 20260105-cross-arch-unwind-7238af40fb14

Best regards,
-- 
Shimin Guo <shimin.guo@skydio.com>
Re: [PATCH v2] perf unwind-libdw: fix a cross-arch unwinding bug
Posted by Namhyung Kim 1 month ago 
Hello,

On Mon, Jan 05, 2026 at 01:13:38PM -0800, Shimin Guo via B4 Relay wrote:
> From: Shimin Guo <shimin.guo@skydio.com>
> 
> The set_initial_registers field of Dwfl_Thread_Callbacks needs to be set
> according to the arch of the stack samples being analyzed, not the arch
> that perf itself is built for. Currently perf fails to unwind stack samples
> collected from archs different from that of the host perf is running on.

Thanks for the contribution!

> This patch moves the arch-specific implementations of set_initial_registers
> from tools/perf/arch to tools/perf/utli/unwind-libdw-arch, similar to the
> way the perf-regs-arch folder contains arch-specific functions related to
> registers, and chooses the implementation based on the arch of the data
> being processed.

I feel like some day we will just include all top-level arch directories
for multi-arch builds..

Btw, can you please show me an example how you tested this?

> 
> Signed-off-by: Shimin Guo <shimin.guo@skydio.com>
> ---
> Changes in v2:
> - Fixed the include path for perf_regs.h in unwind-libdw-x86.c
> - Removed one level of "../" from the include paths in the moved files
> now that they are two directory levels under tools/perf instead of three.
> - Link to v1: https://lore.kernel.org/r/20251223-cross-arch-unwind-v1-1-4d71ee7db512@skydio.com
> ---
>  tools/perf/arch/arm/util/Build                     |  1 -
>  tools/perf/arch/arm64/util/Build                   |  1 -
>  tools/perf/arch/csky/util/Build                    |  2 -
>  tools/perf/arch/powerpc/util/Build                 |  1 -
>  tools/perf/arch/riscv/util/Build                   |  1 -
>  tools/perf/arch/s390/util/Build                    |  2 -
>  tools/perf/arch/x86/util/Build                     |  1 -
>  tools/perf/util/Build                              |  1 +
>  tools/perf/util/unwind-libdw-arch/Build            |  8 ++++
>  .../unwind-libdw-arch/unwind-libdw-arm.c}          | 10 ++---
>  .../unwind-libdw-arch/unwind-libdw-arm64.c}        | 10 ++---
>  .../unwind-libdw-arch/unwind-libdw-csky.c}         |  6 +--
>  .../unwind-libdw-arch/unwind-libdw-loongarch.c}    |  4 +-
>  .../unwind-libdw-arch/unwind-libdw-powerpc.c}      | 10 ++---
>  .../unwind-libdw-arch/unwind-libdw-riscv.c}        |  4 +-
>  .../unwind-libdw-arch/unwind-libdw-s390.c}         |  6 +--
>  .../unwind-libdw-arch/unwind-libdw-x86.c}          |  8 ++--
>  tools/perf/util/unwind-libdw.c                     | 51 +++++++++++++++++++---
>  tools/perf/util/unwind-libdw.h                     | 10 ++++-
>  19 files changed, 92 insertions(+), 45 deletions(-)
> 
> diff --git a/tools/perf/arch/arm/util/Build b/tools/perf/arch/arm/util/Build
> index fd695e1fdaee2ccc300a206131b8b38a763b00ce..3291f893b943df0722dff583523fff4ae79919bc 100644
> --- a/tools/perf/arch/arm/util/Build
> +++ b/tools/perf/arch/arm/util/Build
> @@ -1,6 +1,5 @@
>  perf-util-y += perf_regs.o
>  
>  perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind.o
> -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
>  
>  perf-util-y += pmu.o auxtrace.o cs-etm.o
> diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build
> index d63881081d2eb1e9a83eabf82104d75308f7fc79..0177af19cc00038d6a6005592ddc530bf7eb1557 100644
> --- a/tools/perf/arch/arm64/util/Build
> +++ b/tools/perf/arch/arm64/util/Build
> @@ -1,4 +1,3 @@
> -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
>  perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
>  perf-util-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o
>  perf-util-y += ../../arm/util/auxtrace.o
> diff --git a/tools/perf/arch/csky/util/Build b/tools/perf/arch/csky/util/Build
> index 5e6ea82c42021d3d5651ca4c4a3a6e5138574e4e..6b2d0e021b11464e46d6b53974260d32ea969732 100644
> --- a/tools/perf/arch/csky/util/Build
> +++ b/tools/perf/arch/csky/util/Build
> @@ -1,3 +1 @@
>  perf-util-y += perf_regs.o
> -
> -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> diff --git a/tools/perf/arch/powerpc/util/Build b/tools/perf/arch/powerpc/util/Build
> index 3d0d5427aef7f26a8c05c883cc7ad763f08cbb30..5fd28ec713a4db74ecd1d26866a65ddb20e94bd3 100644
> --- a/tools/perf/arch/powerpc/util/Build
> +++ b/tools/perf/arch/powerpc/util/Build
> @@ -9,5 +9,4 @@ perf-util-y += evsel.o
>  perf-util-$(CONFIG_LIBDW) += skip-callchain-idx.o
>  
>  perf-util-$(CONFIG_LIBUNWIND) += unwind-libunwind.o
> -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
>  perf-util-y += auxtrace.o
> diff --git a/tools/perf/arch/riscv/util/Build b/tools/perf/arch/riscv/util/Build
> index 58a672246024dd0f72e767d11e9958bd9913ec3c..628b9ebd418bde8cdf1ab1332bf79f7c9d50760e 100644
> --- a/tools/perf/arch/riscv/util/Build
> +++ b/tools/perf/arch/riscv/util/Build
> @@ -2,4 +2,3 @@ perf-util-y += perf_regs.o
>  perf-util-y += header.o
>  
>  perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
> -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
> index c64eb18dbdae93adafabf8542e4c9a763ecfe057..5391d26fedd46b7d30a1bef0bff2ec2d58ec30ed 100644
> --- a/tools/perf/arch/s390/util/Build
> +++ b/tools/perf/arch/s390/util/Build
> @@ -2,8 +2,6 @@ perf-util-y += header.o
>  perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
>  perf-util-y += perf_regs.o
>  
> -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> -
>  perf-util-y += machine.o
>  perf-util-y += pmu.o
>  
> diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
> index c0dc5965f3624a6f02525a04d287dff755356d20..fad256252bb95a8f8350b6bb1a54e8074eaebbec 100644
> --- a/tools/perf/arch/x86/util/Build
> +++ b/tools/perf/arch/x86/util/Build
> @@ -12,7 +12,6 @@ perf-util-y += evsel.o
>  perf-util-y += iostat.o
>  
>  perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind.o
> -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
>  
>  perf-util-y += auxtrace.o
>  perf-util-y += archinsn.o
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 1c2a43e1dc68e7f751ec6082352b10de9ffeea62..15f8a4f4b24a46b6300e824f672dd9c0d5b7865f 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -226,6 +226,7 @@ perf-util-$(CONFIG_LIBDW) += debuginfo.o
>  perf-util-$(CONFIG_LIBDW) += annotate-data.o
>  
>  perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arch/
>  perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind-local.o
>  perf-util-$(CONFIG_LIBUNWIND)          += unwind-libunwind.o
>  perf-util-$(CONFIG_LIBUNWIND_X86)      += libunwind/x86_32.o
> diff --git a/tools/perf/util/unwind-libdw-arch/Build b/tools/perf/util/unwind-libdw-arch/Build
> new file mode 100644
> index 0000000000000000000000000000000000000000..e016d54ae2a40ecba47156c8f09cb72156105727
> --- /dev/null
> +++ b/tools/perf/util/unwind-libdw-arch/Build
> @@ -0,0 +1,8 @@
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-x86.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arm.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arm64.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-csky.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-loongarch.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-powerpc.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-riscv.o
> +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-s390.o
> \ No newline at end of file

Please fix.  And I think they can be simply perf-util-y at this point
since you added the directory with CONFIG_LIBDW_DWARF_UNWIND in the
Build file in the parent directory.


> diff --git a/tools/perf/arch/arm/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
> similarity index 78%
> rename from tools/perf/arch/arm/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
> index fbb643f224ec4b27ce9d67051fe0bc4ad555b05e..3c7f91a1af7416f57b0e4fa0dcd15a530cb44f8a 100644
> --- a/tools/perf/arch/arm/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
> @@ -1,11 +1,11 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include <elfutils/libdwfl.h>
> -#include "perf_regs.h"
> -#include "../../../util/unwind-libdw.h"
> -#include "../../../util/perf_regs.h"
> -#include "../../../util/sample.h"
> +#include "../../../arch/arm/include/uapi/asm/perf_regs.h"
> +#include "../../util/unwind-libdw.h"
> +#include "../../util/perf_regs.h"
> +#include "../../util/sample.h"

I think it'd be simpler if we assume the include path always starts from
tools/perf directory (which is set with -I already).  Then we don't need
to change the relative paths when we move files around.

Thanks,
Namhyung

>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_arm(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/arch/arm64/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
> similarity index 86%
> rename from tools/perf/arch/arm64/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
> index b89b0a7e5ad919fed23643d219fbdc3d84deff1e..a237af99d1f87a72b99d5ed2ff965d4ef2f75434 100644
> --- a/tools/perf/arch/arm64/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
> @@ -1,11 +1,11 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include <elfutils/libdwfl.h>
> -#include "perf_regs.h"
> -#include "../../../util/unwind-libdw.h"
> -#include "../../../util/perf_regs.h"
> -#include "../../../util/sample.h"
> +#include "../../../arch/arm64/include/uapi/asm/perf_regs.h"
> +#include "../../util/unwind-libdw.h"
> +#include "../../util/perf_regs.h"
> +#include "../../util/sample.h"
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_arm64(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/arch/csky/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
> similarity index 92%
> rename from tools/perf/arch/csky/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
> index b20b1569783d7e982e91b1b40120d29ccf2f01d1..889d3b788931f3af55b03ef8b91d5def364972e5 100644
> --- a/tools/perf/arch/csky/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
> @@ -2,12 +2,12 @@
>  // Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd.
>  
>  #include <elfutils/libdwfl.h>
> -#include "perf_regs.h"
> +#include "../../../arch/csky/include/uapi/asm/perf_regs.h"
>  #include "../../util/unwind-libdw.h"
>  #include "../../util/perf_regs.h"
> -#include "../../util/event.h"
> +#include "../../util/sample.h"
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_csky(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/arch/loongarch/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
> similarity index 91%
> rename from tools/perf/arch/loongarch/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
> index 60b1144bedd5f325e1512eeab05c29a1e8de2b03..1c5753ace6f63be771aa92365d3174ad8ed3a6fd 100644
> --- a/tools/perf/arch/loongarch/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
> @@ -2,12 +2,12 @@
>  /* Copyright (C) 2020-2023 Loongson Technology Corporation Limited */
>  
>  #include <elfutils/libdwfl.h>
> -#include "perf_regs.h"
> +#include "../../../arch/loongarch/include/uapi/asm/perf_regs.h"
>  #include "../../util/unwind-libdw.h"
>  #include "../../util/perf_regs.h"
>  #include "../../util/sample.h"
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_loongarch(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/arch/powerpc/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
> similarity index 88%
> rename from tools/perf/arch/powerpc/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
> index 82d0c28ae3459ecdb0039cac1f534420d142739b..d5012f20a87e30809b8b44ee20572fab8668b7dd 100644
> --- a/tools/perf/arch/powerpc/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
> @@ -1,10 +1,10 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include <elfutils/libdwfl.h>
>  #include <linux/kernel.h>
> -#include "perf_regs.h"
> -#include "../../../util/unwind-libdw.h"
> -#include "../../../util/perf_regs.h"
> -#include "../../../util/sample.h"
> +#include "../../../arch/powerpc/include/uapi/asm/perf_regs.h"
> +#include "../../util/unwind-libdw.h"
> +#include "../../util/perf_regs.h"
> +#include "../../util/sample.h"
>  
>  /* See backends/ppc_initreg.c and backends/ppc_regs.c in elfutils.  */
>  static const int special_regs[3][2] = {
> @@ -13,7 +13,7 @@ static const int special_regs[3][2] = {
>  	{ 109, PERF_REG_POWERPC_CTR },
>  };
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_powerpc(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/arch/riscv/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
> similarity index 92%
> rename from tools/perf/arch/riscv/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
> index dc1476e16321736de897ad53a00fbc813bd706db..2a5442b3b5bdc27252378de0073deb8a620f8779 100644
> --- a/tools/perf/arch/riscv/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
> @@ -2,12 +2,12 @@
>  /* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
>  
>  #include <elfutils/libdwfl.h>
> -#include "perf_regs.h"
> +#include "../../../arch/riscv/include/uapi/asm/perf_regs.h"
>  #include "../../util/unwind-libdw.h"
>  #include "../../util/perf_regs.h"
>  #include "../../util/sample.h"
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_riscv(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/arch/s390/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
> similarity index 89%
> rename from tools/perf/arch/s390/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
> index c27c7a0d1076c890c35ba19543932c4ed5ac9c2a..18d44074a55bc1c7fa2d7150afc1f1a93d4eadf8 100644
> --- a/tools/perf/arch/s390/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
> @@ -4,11 +4,11 @@
>  #include "../../util/perf_regs.h"
>  #include "../../util/event.h"
>  #include "../../util/sample.h"
> -#include "dwarf-regs-table.h"
> -#include "perf_regs.h"
> +#include "../../arch/s390/include/dwarf-regs-table.h"
> +#include "../../../arch/s390/include/uapi/asm/perf_regs.h"
>  
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_s390(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/arch/x86/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
> similarity index 86%
> rename from tools/perf/arch/x86/util/unwind-libdw.c
> rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
> index 798493e887d7308cb293e29e4ba11054d0fda722..6619c60728ef6ad1e725cd86c7bcbf06b8aad28d 100644
> --- a/tools/perf/arch/x86/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
> @@ -1,11 +1,11 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include <elfutils/libdwfl.h>
> -#include "perf_regs.h"
> -#include "../../../util/unwind-libdw.h"
> -#include "../../../util/perf_regs.h"
> +#include "../../../arch/x86/include/uapi/asm/perf_regs.h"
> +#include "../../util/unwind-libdw.h"
> +#include "../../util/perf_regs.h"
>  #include "util/sample.h"
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg)
>  {
>  	struct unwind_info *ui = arg;
>  	struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
> index ae70fb56a05729b9f06a411d162eabebbf29ac52..f32694ff4ea52d4bf80a38405341864e7ff5e6c8 100644
> --- a/tools/perf/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw.c
> @@ -225,11 +225,45 @@ static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *
>  	return true;
>  }
>  
> -static const Dwfl_Thread_Callbacks callbacks = {
> -	.next_thread		= next_thread,
> -	.memory_read		= memory_read,
> -	.set_initial_registers	= libdw__arch_set_initial_registers,
> -};
> +#define DEFINE_DWFL_THREAD_CALLBACKS(arch)                           \
> +static const Dwfl_Thread_Callbacks callbacks_##arch = {              \
> +	.next_thread           = next_thread,                        \
> +	.memory_read           = memory_read,                        \
> +	.set_initial_registers = libdw_set_initial_registers_##arch, \
> +}
> +
> +DEFINE_DWFL_THREAD_CALLBACKS(x86);
> +DEFINE_DWFL_THREAD_CALLBACKS(arm);
> +DEFINE_DWFL_THREAD_CALLBACKS(arm64);
> +DEFINE_DWFL_THREAD_CALLBACKS(csky);
> +DEFINE_DWFL_THREAD_CALLBACKS(loongarch);
> +DEFINE_DWFL_THREAD_CALLBACKS(powerpc);
> +DEFINE_DWFL_THREAD_CALLBACKS(riscv);
> +DEFINE_DWFL_THREAD_CALLBACKS(s390);
> +
> +static const Dwfl_Thread_Callbacks *get_thread_callbacks(const char *arch)
> +{
> +	if (!strcmp(arch, "arm"))
> +		return &callbacks_arm;
> +	else if (!strcmp(arch, "arm64"))
> +		return &callbacks_arm64;
> +	else if (!strcmp(arch, "csky"))
> +		return &callbacks_csky;
> +	else if (!strcmp(arch, "loongarch"))
> +		return &callbacks_loongarch;
> +	else if (!strcmp(arch, "powerpc"))
> +		return &callbacks_powerpc;
> +	else if (!strcmp(arch, "riscv"))
> +		return &callbacks_riscv;
> +	else if (!strcmp(arch, "s390"))
> +		return &callbacks_s390;
> +	else if (!strcmp(arch, "x86"))
> +		return &callbacks_x86;
> +
> +	pr_err("Fail to get thread callbacks for arch %s, returns NULL\n",
> +	       arch);
> +	return NULL;
> +}
>  
>  static int
>  frame_callback(Dwfl_Frame *state, void *arg)
> @@ -278,6 +312,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
>  	const char *arch = perf_env__arch(ui_buf.machine->env);
>  	Dwarf_Word ip;
>  	int err = -EINVAL, i;
> +	const Dwfl_Thread_Callbacks *callbacks;
>  
>  	if (!data->user_regs || !data->user_regs->regs)
>  		return -EINVAL;
> @@ -300,7 +335,11 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
>  	if (err)
>  		goto out;
>  
> -	err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui);
> +	callbacks = get_thread_callbacks(arch);
> +	if (!callbacks)
> +		goto out;
> +
> +	err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), callbacks, ui);
>  	if (err)
>  		goto out;
>  
> diff --git a/tools/perf/util/unwind-libdw.h b/tools/perf/util/unwind-libdw.h
> index 8c88bc4f2304b59561ffd482469ca63ce0f531f0..574b29848cce31e6bfd93021f752b518cebf73b7 100644
> --- a/tools/perf/util/unwind-libdw.h
> +++ b/tools/perf/util/unwind-libdw.h
> @@ -9,7 +9,15 @@ struct machine;
>  struct perf_sample;
>  struct thread;
>  
> -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_arm(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_arm64(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_csky(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_loongarch(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_mips(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_powerpc(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_riscv(Dwfl_Thread *thread, void *arg);
> +bool libdw_set_initial_registers_s390(Dwfl_Thread *thread, void *arg);
>  
>  struct unwind_info {
>  	Dwfl			*dwfl;
> 
> ---
> base-commit: cbd41c6d4c26c161a2b0e70ad411d3885ff13507
> change-id: 20260105-cross-arch-unwind-7238af40fb14
> 
> Best regards,
> -- 
> Shimin Guo <shimin.guo@skydio.com>
> 
>
Re: [PATCH v2] perf unwind-libdw: fix a cross-arch unwinding bug
Posted by Shimin Guo 1 month ago 
On Tue, Jan 6, 2026 at 11:59 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hello,
>
> On Mon, Jan 05, 2026 at 01:13:38PM -0800, Shimin Guo via B4 Relay wrote:
> > From: Shimin Guo <shimin.guo@skydio.com>
> >
> > The set_initial_registers field of Dwfl_Thread_Callbacks needs to be set
> > according to the arch of the stack samples being analyzed, not the arch
> > that perf itself is built for. Currently perf fails to unwind stack samples
> > collected from archs different from that of the host perf is running on.
>
> Thanks for the contribution!
>
> > This patch moves the arch-specific implementations of set_initial_registers
> > from tools/perf/arch to tools/perf/utli/unwind-libdw-arch, similar to the
> > way the perf-regs-arch folder contains arch-specific functions related to
> > registers, and chooses the implementation based on the arch of the data
> > being processed.
>
> I feel like some day we will just include all top-level arch directories
> for multi-arch builds..
>
> Btw, can you please show me an example how you tested this?

Sure. I initially tested with an embedded target. I also did the
following with qemu:
- run an arm64 ubuntu guest under qemu, where the folder /host is
shared with host
- install sysbench, sysbench-dbgsym, and libc6-dbgsym on the guest
- collect data on the guest:
  sysbench cpu --threads=4 --time=60 run & \
    perf record -a --call-graph dwarf -o /host/perf.data -- sleep 60
- save /proc/kallsyms: cp /proc/kallsyms /host/kallsyms
- Terminate guest. Mount the guest disk image on the host at /mnt/guestroot
- On the host, install libdw1 and libdw-dev.
- On the host, under tools/perf, build perf: make NO_LIBUNWIND=1
NO_LIBTRACEEVENT=1
- On the host, run
  ./perf script -i $SHARED_FOLDER/perf.data --symfs /mnt/guestroot
--kallsyms $SHARED_FOLDER/kallsyms
- Without this patch, I get records like
sysbench    4166 [001]  2309.569275:          5   cycles:
                   e27e0 [unknown] ([unknown])
- With the patch, I get proper backtraces like
sysbench    4166 [001]  2309.569275:          5   cycles:
            aaaab906a338 cpu_execute_event+0x98 (/usr/bin/sysbench)
            aaaab9067a57 worker_thread+0x197 (/usr/bin/sysbench)
            ffffa8940397 start_thread+0x2d7
(/usr/lib/aarch64-linux-gnu/libc.so.6)
            ffffa89a9e9b thread_start+0xb (/usr/lib/aarch64-linux-gnu/libc.so.6)


>
> >
> > Signed-off-by: Shimin Guo <shimin.guo@skydio.com>
> > ---
> > Changes in v2:
> > - Fixed the include path for perf_regs.h in unwind-libdw-x86.c
> > - Removed one level of "../" from the include paths in the moved files
> > now that they are two directory levels under tools/perf instead of three.
> > - Link to v1: https://lore.kernel.org/r/20251223-cross-arch-unwind-v1-1-4d71ee7db512@skydio.com
> > ---
> >  tools/perf/arch/arm/util/Build                     |  1 -
> >  tools/perf/arch/arm64/util/Build                   |  1 -
> >  tools/perf/arch/csky/util/Build                    |  2 -
> >  tools/perf/arch/powerpc/util/Build                 |  1 -
> >  tools/perf/arch/riscv/util/Build                   |  1 -
> >  tools/perf/arch/s390/util/Build                    |  2 -
> >  tools/perf/arch/x86/util/Build                     |  1 -
> >  tools/perf/util/Build                              |  1 +
> >  tools/perf/util/unwind-libdw-arch/Build            |  8 ++++
> >  .../unwind-libdw-arch/unwind-libdw-arm.c}          | 10 ++---
> >  .../unwind-libdw-arch/unwind-libdw-arm64.c}        | 10 ++---
> >  .../unwind-libdw-arch/unwind-libdw-csky.c}         |  6 +--
> >  .../unwind-libdw-arch/unwind-libdw-loongarch.c}    |  4 +-
> >  .../unwind-libdw-arch/unwind-libdw-powerpc.c}      | 10 ++---
> >  .../unwind-libdw-arch/unwind-libdw-riscv.c}        |  4 +-
> >  .../unwind-libdw-arch/unwind-libdw-s390.c}         |  6 +--
> >  .../unwind-libdw-arch/unwind-libdw-x86.c}          |  8 ++--
> >  tools/perf/util/unwind-libdw.c                     | 51 +++++++++++++++++++---
> >  tools/perf/util/unwind-libdw.h                     | 10 ++++-
> >  19 files changed, 92 insertions(+), 45 deletions(-)
> >
> > diff --git a/tools/perf/arch/arm/util/Build b/tools/perf/arch/arm/util/Build
> > index fd695e1fdaee2ccc300a206131b8b38a763b00ce..3291f893b943df0722dff583523fff4ae79919bc 100644
> > --- a/tools/perf/arch/arm/util/Build
> > +++ b/tools/perf/arch/arm/util/Build
> > @@ -1,6 +1,5 @@
> >  perf-util-y += perf_regs.o
> >
> >  perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind.o
> > -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> >
> >  perf-util-y += pmu.o auxtrace.o cs-etm.o
> > diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build
> > index d63881081d2eb1e9a83eabf82104d75308f7fc79..0177af19cc00038d6a6005592ddc530bf7eb1557 100644
> > --- a/tools/perf/arch/arm64/util/Build
> > +++ b/tools/perf/arch/arm64/util/Build
> > @@ -1,4 +1,3 @@
> > -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> >  perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
> >  perf-util-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o
> >  perf-util-y += ../../arm/util/auxtrace.o
> > diff --git a/tools/perf/arch/csky/util/Build b/tools/perf/arch/csky/util/Build
> > index 5e6ea82c42021d3d5651ca4c4a3a6e5138574e4e..6b2d0e021b11464e46d6b53974260d32ea969732 100644
> > --- a/tools/perf/arch/csky/util/Build
> > +++ b/tools/perf/arch/csky/util/Build
> > @@ -1,3 +1 @@
> >  perf-util-y += perf_regs.o
> > -
> > -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> > diff --git a/tools/perf/arch/powerpc/util/Build b/tools/perf/arch/powerpc/util/Build
> > index 3d0d5427aef7f26a8c05c883cc7ad763f08cbb30..5fd28ec713a4db74ecd1d26866a65ddb20e94bd3 100644
> > --- a/tools/perf/arch/powerpc/util/Build
> > +++ b/tools/perf/arch/powerpc/util/Build
> > @@ -9,5 +9,4 @@ perf-util-y += evsel.o
> >  perf-util-$(CONFIG_LIBDW) += skip-callchain-idx.o
> >
> >  perf-util-$(CONFIG_LIBUNWIND) += unwind-libunwind.o
> > -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> >  perf-util-y += auxtrace.o
> > diff --git a/tools/perf/arch/riscv/util/Build b/tools/perf/arch/riscv/util/Build
> > index 58a672246024dd0f72e767d11e9958bd9913ec3c..628b9ebd418bde8cdf1ab1332bf79f7c9d50760e 100644
> > --- a/tools/perf/arch/riscv/util/Build
> > +++ b/tools/perf/arch/riscv/util/Build
> > @@ -2,4 +2,3 @@ perf-util-y += perf_regs.o
> >  perf-util-y += header.o
> >
> >  perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
> > -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> > diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
> > index c64eb18dbdae93adafabf8542e4c9a763ecfe057..5391d26fedd46b7d30a1bef0bff2ec2d58ec30ed 100644
> > --- a/tools/perf/arch/s390/util/Build
> > +++ b/tools/perf/arch/s390/util/Build
> > @@ -2,8 +2,6 @@ perf-util-y += header.o
> >  perf-util-$(CONFIG_LIBTRACEEVENT) += kvm-stat.o
> >  perf-util-y += perf_regs.o
> >
> > -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> > -
> >  perf-util-y += machine.o
> >  perf-util-y += pmu.o
> >
> > diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
> > index c0dc5965f3624a6f02525a04d287dff755356d20..fad256252bb95a8f8350b6bb1a54e8074eaebbec 100644
> > --- a/tools/perf/arch/x86/util/Build
> > +++ b/tools/perf/arch/x86/util/Build
> > @@ -12,7 +12,6 @@ perf-util-y += evsel.o
> >  perf-util-y += iostat.o
> >
> >  perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind.o
> > -perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> >
> >  perf-util-y += auxtrace.o
> >  perf-util-y += archinsn.o
> > diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> > index 1c2a43e1dc68e7f751ec6082352b10de9ffeea62..15f8a4f4b24a46b6300e824f672dd9c0d5b7865f 100644
> > --- a/tools/perf/util/Build
> > +++ b/tools/perf/util/Build
> > @@ -226,6 +226,7 @@ perf-util-$(CONFIG_LIBDW) += debuginfo.o
> >  perf-util-$(CONFIG_LIBDW) += annotate-data.o
> >
> >  perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arch/
> >  perf-util-$(CONFIG_LOCAL_LIBUNWIND)    += unwind-libunwind-local.o
> >  perf-util-$(CONFIG_LIBUNWIND)          += unwind-libunwind.o
> >  perf-util-$(CONFIG_LIBUNWIND_X86)      += libunwind/x86_32.o
> > diff --git a/tools/perf/util/unwind-libdw-arch/Build b/tools/perf/util/unwind-libdw-arch/Build
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..e016d54ae2a40ecba47156c8f09cb72156105727
> > --- /dev/null
> > +++ b/tools/perf/util/unwind-libdw-arch/Build
> > @@ -0,0 +1,8 @@
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-x86.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arm.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-arm64.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-csky.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-loongarch.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-powerpc.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-riscv.o
> > +perf-util-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw-s390.o
> > \ No newline at end of file
>
> Please fix.  And I think they can be simply perf-util-y at this point
> since you added the directory with CONFIG_LIBDW_DWARF_UNWIND in the
> Build file in the parent directory.

Will fix in the next version.

>
>
> > diff --git a/tools/perf/arch/arm/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
> > similarity index 78%
> > rename from tools/perf/arch/arm/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
> > index fbb643f224ec4b27ce9d67051fe0bc4ad555b05e..3c7f91a1af7416f57b0e4fa0dcd15a530cb44f8a 100644
> > --- a/tools/perf/arch/arm/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm.c
> > @@ -1,11 +1,11 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <elfutils/libdwfl.h>
> > -#include "perf_regs.h"
> > -#include "../../../util/unwind-libdw.h"
> > -#include "../../../util/perf_regs.h"
> > -#include "../../../util/sample.h"
> > +#include "../../../arch/arm/include/uapi/asm/perf_regs.h"
> > +#include "../../util/unwind-libdw.h"
> > +#include "../../util/perf_regs.h"
> > +#include "../../util/sample.h"
>
> I think it'd be simpler if we assume the include path always starts from
> tools/perf directory (which is set with -I already).  Then we don't need
> to change the relative paths when we move files around.

Will fix in the next version.

>
> Thanks,
> Namhyung
>
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_arm(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/arch/arm64/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
> > similarity index 86%
> > rename from tools/perf/arch/arm64/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
> > index b89b0a7e5ad919fed23643d219fbdc3d84deff1e..a237af99d1f87a72b99d5ed2ff965d4ef2f75434 100644
> > --- a/tools/perf/arch/arm64/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-arm64.c
> > @@ -1,11 +1,11 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <elfutils/libdwfl.h>
> > -#include "perf_regs.h"
> > -#include "../../../util/unwind-libdw.h"
> > -#include "../../../util/perf_regs.h"
> > -#include "../../../util/sample.h"
> > +#include "../../../arch/arm64/include/uapi/asm/perf_regs.h"
> > +#include "../../util/unwind-libdw.h"
> > +#include "../../util/perf_regs.h"
> > +#include "../../util/sample.h"
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_arm64(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/arch/csky/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
> > similarity index 92%
> > rename from tools/perf/arch/csky/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
> > index b20b1569783d7e982e91b1b40120d29ccf2f01d1..889d3b788931f3af55b03ef8b91d5def364972e5 100644
> > --- a/tools/perf/arch/csky/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-csky.c
> > @@ -2,12 +2,12 @@
> >  // Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd.
> >
> >  #include <elfutils/libdwfl.h>
> > -#include "perf_regs.h"
> > +#include "../../../arch/csky/include/uapi/asm/perf_regs.h"
> >  #include "../../util/unwind-libdw.h"
> >  #include "../../util/perf_regs.h"
> > -#include "../../util/event.h"
> > +#include "../../util/sample.h"
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_csky(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/arch/loongarch/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
> > similarity index 91%
> > rename from tools/perf/arch/loongarch/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
> > index 60b1144bedd5f325e1512eeab05c29a1e8de2b03..1c5753ace6f63be771aa92365d3174ad8ed3a6fd 100644
> > --- a/tools/perf/arch/loongarch/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-loongarch.c
> > @@ -2,12 +2,12 @@
> >  /* Copyright (C) 2020-2023 Loongson Technology Corporation Limited */
> >
> >  #include <elfutils/libdwfl.h>
> > -#include "perf_regs.h"
> > +#include "../../../arch/loongarch/include/uapi/asm/perf_regs.h"
> >  #include "../../util/unwind-libdw.h"
> >  #include "../../util/perf_regs.h"
> >  #include "../../util/sample.h"
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_loongarch(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/arch/powerpc/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
> > similarity index 88%
> > rename from tools/perf/arch/powerpc/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
> > index 82d0c28ae3459ecdb0039cac1f534420d142739b..d5012f20a87e30809b8b44ee20572fab8668b7dd 100644
> > --- a/tools/perf/arch/powerpc/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-powerpc.c
> > @@ -1,10 +1,10 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <elfutils/libdwfl.h>
> >  #include <linux/kernel.h>
> > -#include "perf_regs.h"
> > -#include "../../../util/unwind-libdw.h"
> > -#include "../../../util/perf_regs.h"
> > -#include "../../../util/sample.h"
> > +#include "../../../arch/powerpc/include/uapi/asm/perf_regs.h"
> > +#include "../../util/unwind-libdw.h"
> > +#include "../../util/perf_regs.h"
> > +#include "../../util/sample.h"
> >
> >  /* See backends/ppc_initreg.c and backends/ppc_regs.c in elfutils.  */
> >  static const int special_regs[3][2] = {
> > @@ -13,7 +13,7 @@ static const int special_regs[3][2] = {
> >       { 109, PERF_REG_POWERPC_CTR },
> >  };
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_powerpc(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/arch/riscv/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
> > similarity index 92%
> > rename from tools/perf/arch/riscv/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
> > index dc1476e16321736de897ad53a00fbc813bd706db..2a5442b3b5bdc27252378de0073deb8a620f8779 100644
> > --- a/tools/perf/arch/riscv/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-riscv.c
> > @@ -2,12 +2,12 @@
> >  /* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
> >
> >  #include <elfutils/libdwfl.h>
> > -#include "perf_regs.h"
> > +#include "../../../arch/riscv/include/uapi/asm/perf_regs.h"
> >  #include "../../util/unwind-libdw.h"
> >  #include "../../util/perf_regs.h"
> >  #include "../../util/sample.h"
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_riscv(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/arch/s390/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
> > similarity index 89%
> > rename from tools/perf/arch/s390/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
> > index c27c7a0d1076c890c35ba19543932c4ed5ac9c2a..18d44074a55bc1c7fa2d7150afc1f1a93d4eadf8 100644
> > --- a/tools/perf/arch/s390/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-s390.c
> > @@ -4,11 +4,11 @@
> >  #include "../../util/perf_regs.h"
> >  #include "../../util/event.h"
> >  #include "../../util/sample.h"
> > -#include "dwarf-regs-table.h"
> > -#include "perf_regs.h"
> > +#include "../../arch/s390/include/dwarf-regs-table.h"
> > +#include "../../../arch/s390/include/uapi/asm/perf_regs.h"
> >
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_s390(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/arch/x86/util/unwind-libdw.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
> > similarity index 86%
> > rename from tools/perf/arch/x86/util/unwind-libdw.c
> > rename to tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
> > index 798493e887d7308cb293e29e4ba11054d0fda722..6619c60728ef6ad1e725cd86c7bcbf06b8aad28d 100644
> > --- a/tools/perf/arch/x86/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
> > @@ -1,11 +1,11 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <elfutils/libdwfl.h>
> > -#include "perf_regs.h"
> > -#include "../../../util/unwind-libdw.h"
> > -#include "../../../util/perf_regs.h"
> > +#include "../../../arch/x86/include/uapi/asm/perf_regs.h"
> > +#include "../../util/unwind-libdw.h"
> > +#include "../../util/perf_regs.h"
> >  #include "util/sample.h"
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> > +bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg)
> >  {
> >       struct unwind_info *ui = arg;
> >       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
> > diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
> > index ae70fb56a05729b9f06a411d162eabebbf29ac52..f32694ff4ea52d4bf80a38405341864e7ff5e6c8 100644
> > --- a/tools/perf/util/unwind-libdw.c
> > +++ b/tools/perf/util/unwind-libdw.c
> > @@ -225,11 +225,45 @@ static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *
> >       return true;
> >  }
> >
> > -static const Dwfl_Thread_Callbacks callbacks = {
> > -     .next_thread            = next_thread,
> > -     .memory_read            = memory_read,
> > -     .set_initial_registers  = libdw__arch_set_initial_registers,
> > -};
> > +#define DEFINE_DWFL_THREAD_CALLBACKS(arch)                           \
> > +static const Dwfl_Thread_Callbacks callbacks_##arch = {              \
> > +     .next_thread           = next_thread,                        \
> > +     .memory_read           = memory_read,                        \
> > +     .set_initial_registers = libdw_set_initial_registers_##arch, \
> > +}
> > +
> > +DEFINE_DWFL_THREAD_CALLBACKS(x86);
> > +DEFINE_DWFL_THREAD_CALLBACKS(arm);
> > +DEFINE_DWFL_THREAD_CALLBACKS(arm64);
> > +DEFINE_DWFL_THREAD_CALLBACKS(csky);
> > +DEFINE_DWFL_THREAD_CALLBACKS(loongarch);
> > +DEFINE_DWFL_THREAD_CALLBACKS(powerpc);
> > +DEFINE_DWFL_THREAD_CALLBACKS(riscv);
> > +DEFINE_DWFL_THREAD_CALLBACKS(s390);
> > +
> > +static const Dwfl_Thread_Callbacks *get_thread_callbacks(const char *arch)
> > +{
> > +     if (!strcmp(arch, "arm"))
> > +             return &callbacks_arm;
> > +     else if (!strcmp(arch, "arm64"))
> > +             return &callbacks_arm64;
> > +     else if (!strcmp(arch, "csky"))
> > +             return &callbacks_csky;
> > +     else if (!strcmp(arch, "loongarch"))
> > +             return &callbacks_loongarch;
> > +     else if (!strcmp(arch, "powerpc"))
> > +             return &callbacks_powerpc;
> > +     else if (!strcmp(arch, "riscv"))
> > +             return &callbacks_riscv;
> > +     else if (!strcmp(arch, "s390"))
> > +             return &callbacks_s390;
> > +     else if (!strcmp(arch, "x86"))
> > +             return &callbacks_x86;
> > +
> > +     pr_err("Fail to get thread callbacks for arch %s, returns NULL\n",
> > +            arch);
> > +     return NULL;
> > +}
> >
> >  static int
> >  frame_callback(Dwfl_Frame *state, void *arg)
> > @@ -278,6 +312,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
> >       const char *arch = perf_env__arch(ui_buf.machine->env);
> >       Dwarf_Word ip;
> >       int err = -EINVAL, i;
> > +     const Dwfl_Thread_Callbacks *callbacks;
> >
> >       if (!data->user_regs || !data->user_regs->regs)
> >               return -EINVAL;
> > @@ -300,7 +335,11 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
> >       if (err)
> >               goto out;
> >
> > -     err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui);
> > +     callbacks = get_thread_callbacks(arch);
> > +     if (!callbacks)
> > +             goto out;
> > +
> > +     err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), callbacks, ui);
> >       if (err)
> >               goto out;
> >
> > diff --git a/tools/perf/util/unwind-libdw.h b/tools/perf/util/unwind-libdw.h
> > index 8c88bc4f2304b59561ffd482469ca63ce0f531f0..574b29848cce31e6bfd93021f752b518cebf73b7 100644
> > --- a/tools/perf/util/unwind-libdw.h
> > +++ b/tools/perf/util/unwind-libdw.h
> > @@ -9,7 +9,15 @@ struct machine;
> >  struct perf_sample;
> >  struct thread;
> >
> > -bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_arm(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_arm64(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_csky(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_loongarch(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_mips(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_powerpc(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_riscv(Dwfl_Thread *thread, void *arg);
> > +bool libdw_set_initial_registers_s390(Dwfl_Thread *thread, void *arg);
> >
> >  struct unwind_info {
> >       Dwfl                    *dwfl;
> >
> > ---
> > base-commit: cbd41c6d4c26c161a2b0e70ad411d3885ff13507
> > change-id: 20260105-cross-arch-unwind-7238af40fb14
> >
> > Best regards,
> > --
> > Shimin Guo <shimin.guo@skydio.com>
> >
> >

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