From: Josh Poimboeuf <jpoimboe@kernel.org>
Use ARCH_INIT_USER_FP_FRAME to describe how frame pointers are unwound
on x86, and enable CONFIG_HAVE_UNWIND_USER_FP accordingly so the
unwind_user interfaces can be used.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/unwind_user.h | 11 +++++++++++
2 files changed, 12 insertions(+)
create mode 100644 arch/x86/include/asm/unwind_user.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 58d890fe2100..8f94c58d4de8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -299,6 +299,7 @@ config X86
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
select HAVE_UNSTABLE_SCHED_CLOCK
+ select HAVE_UNWIND_USER_FP if X86_64
select HAVE_USER_RETURN_NOTIFIER
select HAVE_GENERIC_VDSO
select VDSO_GETRANDOM if X86_64
diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
new file mode 100644
index 000000000000..8597857bf896
--- /dev/null
+++ b/arch/x86/include/asm/unwind_user.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_UNWIND_USER_H
+#define _ASM_X86_UNWIND_USER_H
+
+#define ARCH_INIT_USER_FP_FRAME \
+ .cfa_off = (s32)sizeof(long) * 2, \
+ .ra_off = (s32)sizeof(long) * -1, \
+ .fp_off = (s32)sizeof(long) * -2, \
+ .use_fp = true,
+
+#endif /* _ASM_X86_UNWIND_USER_H */
--
2.50.1On Wed, Aug 27, 2025 at 03:36:45PM -0400, Steven Rostedt wrote:
> From: Josh Poimboeuf <jpoimboe@kernel.org>
>
> Use ARCH_INIT_USER_FP_FRAME to describe how frame pointers are unwound
> on x86, and enable CONFIG_HAVE_UNWIND_USER_FP accordingly so the
> unwind_user interfaces can be used.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/include/asm/unwind_user.h | 11 +++++++++++
> 2 files changed, 12 insertions(+)
> create mode 100644 arch/x86/include/asm/unwind_user.h
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 58d890fe2100..8f94c58d4de8 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -299,6 +299,7 @@ config X86
> select HAVE_SYSCALL_TRACEPOINTS
> select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
> select HAVE_UNSTABLE_SCHED_CLOCK
> + select HAVE_UNWIND_USER_FP if X86_64
> select HAVE_USER_RETURN_NOTIFIER
> select HAVE_GENERIC_VDSO
> select VDSO_GETRANDOM if X86_64
> diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
> new file mode 100644
> index 000000000000..8597857bf896
> --- /dev/null
> +++ b/arch/x86/include/asm/unwind_user.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_X86_UNWIND_USER_H
> +#define _ASM_X86_UNWIND_USER_H
> +
> +#define ARCH_INIT_USER_FP_FRAME \
> + .cfa_off = (s32)sizeof(long) * 2, \
> + .ra_off = (s32)sizeof(long) * -1, \
> + .fp_off = (s32)sizeof(long) * -2, \
> + .use_fp = true,
> +
> +#endif /* _ASM_X86_UNWIND_USER_H */
Moo, and now you have me look at unwind/user.c:
/* Make sure that the address is word aligned */
shift = sizeof(long) == 4 ? 2 : 3;
if (cfa & ((1 << shift) - 1))
return -EINVAL;
Isn't that just:
if (cfa & (sizeof(long) - 1))
?
Let me go add a patch to clean that up...
On Tue, 23 Sep 2025 12:51:30 +0200 Peter Zijlstra <peterz@infradead.org> wrote: > Moo, and now you have me look at unwind/user.c: > > /* Make sure that the address is word aligned */ > shift = sizeof(long) == 4 ? 2 : 3; > if (cfa & ((1 << shift) - 1)) > return -EINVAL; > > Isn't that just: > > if (cfa & (sizeof(long) - 1)) > > ? > > Let me go add a patch to clean that up... Sure, as long as it's commented. Thanks, -- Steve
The following commit has been merged into the perf/core branch of tip:
Commit-ID: 49cf34c0815f93fb2ea3ab5cfbac1124bd9b45d0
Gitweb: https://git.kernel.org/tip/49cf34c0815f93fb2ea3ab5cfbac1124bd9b45d0
Author: Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate: Wed, 27 Aug 2025 15:36:45 -04:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 29 Oct 2025 10:29:58 +01:00
unwind_user/x86: Enable frame pointer unwinding on x86
Use ARCH_INIT_USER_FP_FRAME to describe how frame pointers are unwound
on x86, and enable CONFIG_HAVE_UNWIND_USER_FP accordingly so the
unwind_user interfaces can be used.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20250827193828.347397433@kernel.org
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/unwind_user.h | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+)
create mode 100644 arch/x86/include/asm/unwind_user.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fa3b616..5cf1afc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -297,6 +297,7 @@ config X86
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
select HAVE_UNSTABLE_SCHED_CLOCK
+ select HAVE_UNWIND_USER_FP if X86_64
select HAVE_USER_RETURN_NOTIFIER
select HAVE_GENERIC_VDSO
select VDSO_GETRANDOM if X86_64
diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
new file mode 100644
index 0000000..b166e10
--- /dev/null
+++ b/arch/x86/include/asm/unwind_user.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_UNWIND_USER_H
+#define _ASM_X86_UNWIND_USER_H
+
+#include <asm/ptrace.h>
+
+#define ARCH_INIT_USER_FP_FRAME(ws) \
+ .cfa_off = 2*(ws), \
+ .ra_off = -1*(ws), \
+ .fp_off = -2*(ws), \
+ .use_fp = true,
+
+static inline int unwind_user_word_size(struct pt_regs *regs)
+{
+ /* We can't unwind VM86 stacks */
+ if (regs->flags & X86_VM_MASK)
+ return 0;
+#ifdef CONFIG_X86_64
+ if (!user_64bit_mode(regs))
+ return sizeof(int);
+#endif
+ return sizeof(long);
+}
+
+#endif /* _ASM_X86_UNWIND_USER_H */© 2016 - 2026 Red Hat, Inc.