After binutils commit e43d876 which was first included in binutils 2.41,
riscv no longer supports dumping in the middle of instructions. Increase
the objdump window by 2-bytes to ensure that any instruction that sits
on the boundary of the specified stop-address is not cut in half.
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
arch/riscv/Kconfig | 5 +++++
tools/perf/tests/code-reading.c | 17 ++++++++++++++++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index d4a7ca0388c071b536df59c0eb11d55f9080c7cd..f164047471267936bc62389b7d7d9a7cbdca8f97 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -229,6 +229,11 @@ config GCC_SUPPORTS_DYNAMIC_FTRACE
def_bool CC_IS_GCC
depends on $(cc-option,-fpatchable-function-entry=8)
+config RISCV_OBJDUMP_SUPPORTS_SPLIT_INSTRUCTION
+ # Some versions of objdump do not support dumping partial instructions
+ def_bool y
+ depends on !(OBJDUMP_IS_GNU && OBJDUMP_VERSION > 24100)
+
config HAVE_SHADOW_CALL_STACK
def_bool $(cc-option,-fsanitize=shadow-call-stack)
# https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/a484e843e6eeb51f0cb7b8819e50da6d2444d769
diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index 27c82cfb7e7de42284bf5af9cf7594a3a963052e..605f4a8e1dbc00d8a572503f45053c2f30ad19e3 100644
--- a/tools/perf/tests/code-reading.c
+++ b/tools/perf/tests/code-reading.c
@@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
+#include <linux/kconfig.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <inttypes.h>
@@ -183,9 +184,23 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
const char *fmt;
FILE *f;
int ret;
+ u64 stop_address = addr + len;
+
+ if (IS_ENABLED(__riscv) && !IS_ENABLED(CONFIG_RISCV_OBJDUMP_SUPPORTS_SPLIT_INSTRUCTION)) {
+ /*
+ * On some versions of riscv objdump, dumping in the middle of
+ * instructions is not supported. riscv instructions are aligned along
+ * 2-byte intervals and can be either 2-bytes or 4-bytes. This makes it
+ * possible that the stop-address lands in the middle of a 4-byte
+ * instruction. Increase the stop_address by two to ensure an
+ * instruction is not cut in half, but leave the len as-is so only the
+ * expected number of bytes are collected.
+ */
+ stop_address += 2;
+ }
fmt = "%s -z -d --start-address=0x%"PRIx64" --stop-address=0x%"PRIx64" %s";
- ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, addr + len,
+ ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, stop_address,
filename);
if (ret <= 0 || (size_t)ret >= sizeof(cmd))
return -1;
--
2.34.1On Mon, Dec 16, 2024 at 3:13 PM Charlie Jenkins <charlie@rivosinc.com> wrote:
>
> After binutils commit e43d876 which was first included in binutils 2.41,
> riscv no longer supports dumping in the middle of instructions. Increase
> the objdump window by 2-bytes to ensure that any instruction that sits
> on the boundary of the specified stop-address is not cut in half.
>
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> ---
> arch/riscv/Kconfig | 5 +++++
> tools/perf/tests/code-reading.c | 17 ++++++++++++++++-
Files under tools use a different Build system than the kernel. The
Kconfig value won't have an effect. Check out Makefile.config:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/Makefile.config?h=perf-tools-next
which is included into the build here:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/Makefile.perf?h=perf-tools-next#n313
> 2 files changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index d4a7ca0388c071b536df59c0eb11d55f9080c7cd..f164047471267936bc62389b7d7d9a7cbdca8f97 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -229,6 +229,11 @@ config GCC_SUPPORTS_DYNAMIC_FTRACE
> def_bool CC_IS_GCC
> depends on $(cc-option,-fpatchable-function-entry=8)
>
> +config RISCV_OBJDUMP_SUPPORTS_SPLIT_INSTRUCTION
> + # Some versions of objdump do not support dumping partial instructions
> + def_bool y
> + depends on !(OBJDUMP_IS_GNU && OBJDUMP_VERSION > 24100)
> +
> config HAVE_SHADOW_CALL_STACK
> def_bool $(cc-option,-fsanitize=shadow-call-stack)
> # https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/a484e843e6eeb51f0cb7b8819e50da6d2444d769
> diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
> index 27c82cfb7e7de42284bf5af9cf7594a3a963052e..605f4a8e1dbc00d8a572503f45053c2f30ad19e3 100644
> --- a/tools/perf/tests/code-reading.c
> +++ b/tools/perf/tests/code-reading.c
> @@ -1,5 +1,6 @@
> // SPDX-License-Identifier: GPL-2.0
> #include <errno.h>
> +#include <linux/kconfig.h>
> #include <linux/kernel.h>
> #include <linux/types.h>
> #include <inttypes.h>
> @@ -183,9 +184,23 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
> const char *fmt;
> FILE *f;
> int ret;
> + u64 stop_address = addr + len;
> +
> + if (IS_ENABLED(__riscv) && !IS_ENABLED(CONFIG_RISCV_OBJDUMP_SUPPORTS_SPLIT_INSTRUCTION)) {
It would be nice if this could be a runtime rather than build time detected.
Thanks,
Ian
> + /*
> + * On some versions of riscv objdump, dumping in the middle of
> + * instructions is not supported. riscv instructions are aligned along
> + * 2-byte intervals and can be either 2-bytes or 4-bytes. This makes it
> + * possible that the stop-address lands in the middle of a 4-byte
> + * instruction. Increase the stop_address by two to ensure an
> + * instruction is not cut in half, but leave the len as-is so only the
> + * expected number of bytes are collected.
> + */
> + stop_address += 2;
> + }
>
> fmt = "%s -z -d --start-address=0x%"PRIx64" --stop-address=0x%"PRIx64" %s";
> - ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, addr + len,
> + ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, stop_address,
> filename);
> if (ret <= 0 || (size_t)ret >= sizeof(cmd))
> return -1;
>
> --
> 2.34.1
>
On Mon, Dec 16, 2024 at 08:57:20PM -0800, Ian Rogers wrote:
> On Mon, Dec 16, 2024 at 3:13 PM Charlie Jenkins <charlie@rivosinc.com> wrote:
> >
> > After binutils commit e43d876 which was first included in binutils 2.41,
> > riscv no longer supports dumping in the middle of instructions. Increase
> > the objdump window by 2-bytes to ensure that any instruction that sits
> > on the boundary of the specified stop-address is not cut in half.
> >
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > ---
> > arch/riscv/Kconfig | 5 +++++
> > tools/perf/tests/code-reading.c | 17 ++++++++++++++++-
>
> Files under tools use a different Build system than the kernel. The
> Kconfig value won't have an effect. Check out Makefile.config:
> https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/Makefile.config?h=perf-tools-next
> which is included into the build here:
> https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/Makefile.perf?h=perf-tools-next#n313
>
Ahh okay, thank you. It was properly enabling when I was testing, is
there some bleeding over?
> > 2 files changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index d4a7ca0388c071b536df59c0eb11d55f9080c7cd..f164047471267936bc62389b7d7d9a7cbdca8f97 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -229,6 +229,11 @@ config GCC_SUPPORTS_DYNAMIC_FTRACE
> > def_bool CC_IS_GCC
> > depends on $(cc-option,-fpatchable-function-entry=8)
> >
> > +config RISCV_OBJDUMP_SUPPORTS_SPLIT_INSTRUCTION
> > + # Some versions of objdump do not support dumping partial instructions
> > + def_bool y
> > + depends on !(OBJDUMP_IS_GNU && OBJDUMP_VERSION > 24100)
> > +
> > config HAVE_SHADOW_CALL_STACK
> > def_bool $(cc-option,-fsanitize=shadow-call-stack)
> > # https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/a484e843e6eeb51f0cb7b8819e50da6d2444d769
> > diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
> > index 27c82cfb7e7de42284bf5af9cf7594a3a963052e..605f4a8e1dbc00d8a572503f45053c2f30ad19e3 100644
> > --- a/tools/perf/tests/code-reading.c
> > +++ b/tools/perf/tests/code-reading.c
> > @@ -1,5 +1,6 @@
> > // SPDX-License-Identifier: GPL-2.0
> > #include <errno.h>
> > +#include <linux/kconfig.h>
> > #include <linux/kernel.h>
> > #include <linux/types.h>
> > #include <inttypes.h>
> > @@ -183,9 +184,23 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
> > const char *fmt;
> > FILE *f;
> > int ret;
> > + u64 stop_address = addr + len;
> > +
> > + if (IS_ENABLED(__riscv) && !IS_ENABLED(CONFIG_RISCV_OBJDUMP_SUPPORTS_SPLIT_INSTRUCTION)) {
>
> It would be nice if this could be a runtime rather than build time detected.
Hmm that is a good point. I will change this to check the version at
runtime.
- Charlie
>
> Thanks,
> Ian
>
> > + /*
> > + * On some versions of riscv objdump, dumping in the middle of
> > + * instructions is not supported. riscv instructions are aligned along
> > + * 2-byte intervals and can be either 2-bytes or 4-bytes. This makes it
> > + * possible that the stop-address lands in the middle of a 4-byte
> > + * instruction. Increase the stop_address by two to ensure an
> > + * instruction is not cut in half, but leave the len as-is so only the
> > + * expected number of bytes are collected.
> > + */
> > + stop_address += 2;
> > + }
> >
> > fmt = "%s -z -d --start-address=0x%"PRIx64" --stop-address=0x%"PRIx64" %s";
> > - ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, addr + len,
> > + ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, stop_address,
> > filename);
> > if (ret <= 0 || (size_t)ret >= sizeof(cmd))
> > return -1;
> >
> > --
> > 2.34.1
> >
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