Perf failed to add kretprobe event with debuginfo of vmlinux which is
compiled by gcc with -fpatchable-function-entry option enabled.
The same issue with kernel module.
Issue:
# perf probe -v 'kernel_clone%return $retval'
......
Writing event: r:probe/kernel_clone__return _text+599624 $retval
Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
# cat /sys/kernel/debug/tracing/error_log
[156.75] trace_kprobe: error: Retprobe address must be an function entry
Command: r:probe/kernel_clone__return _text+599624 $retval
^
# llvm-dwarfdump vmlinux |grep -A 10 -w 0x00df2c2b
0x00df2c2b: DW_TAG_subprogram
DW_AT_external (true)
DW_AT_name ("kernel_clone")
DW_AT_decl_file ("/home/code/linux-next/kernel/fork.c")
DW_AT_decl_line (2423)
DW_AT_decl_column (0x07)
DW_AT_prototyped (true)
DW_AT_type (0x00dcd492 "pid_t")
DW_AT_low_pc (0xffff800010092648)
DW_AT_high_pc (0xffff800010092b9c)
DW_AT_frame_base (DW_OP_call_frame_cfa)
# cat /proc/kallsyms |grep kernel_clone
ffff800010092640 T kernel_clone
# readelf -s vmlinux |grep -i kernel_clone
183173: ffff800010092640 1372 FUNC GLOBAL DEFAULT 2 kernel_clone
# objdump -d vmlinux |grep -A 10 -w \<kernel_clone\>:
ffff800010092640 <kernel_clone>:
ffff800010092640: d503201f nop
ffff800010092644: d503201f nop
ffff800010092648: d503233f paciasp
ffff80001009264c: a9b87bfd stp x29, x30, [sp, #-128]!
ffff800010092650: 910003fd mov x29, sp
ffff800010092654: a90153f3 stp x19, x20, [sp, #16]
The entry address of kernel_clone converted by debuginfo is _text+599624
(0x92648), which is consistent with the value of DW_AT_low_pc attribute.
But the symbolic address of kernel_clone from /proc/kallsyms is
ffff800010092640.
This issue is found on arm64, -fpatchable-function-entry=2 is enabled when
CONFIG_DYNAMIC_FTRACE_WITH_REGS=y;
Just as objdump displayed the assembler contents of kernel_clone,
GCC generate 2 NOPs at the beginning of each function.
kprobe_on_func_entry detects that (_text+599624) is not the entry address
of the function, which leads to the failure of adding kretprobe event.
kprobe_on_func_entry
->_kprobe_addr
->kallsyms_lookup_size_offset
->arch_kprobe_on_func_entry // FALSE
The cause of the issue is that the first instruction in the compile unit
indicated by DW_AT_low_pc does not include NOPs.
This issue exists in all gcc versions that support
-fpatchable-function-entry option.
I have reported it to the GCC community:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98776
Currently arm64 and PA-RISC may enable fpatchable-function-entry option.
The kernel compiled with clang does not have this issue.
FIX:
This GCC issue only cause the registration failure of the kretprobe event
which doesn't need debuginfo. So, stop using debuginfo for retprobe.
map will be used to query the probe function address.
Signed-off-by: Jianlin Lv <[email protected]>
---
v2: stop using debuginfo for retprobe, and update changelog.
v3: Update changelog, fixed misuse of --- marker.
---
tools/perf/util/probe-event.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 8eae2afff71a..a59d3268adb0 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -894,6 +894,16 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
struct debuginfo *dinfo;
int ntevs, ret = 0;
+ /* Workaround for gcc #98776 issue.
+ * Perf failed to add kretprobe event with debuginfo of vmlinux which is
+ * compiled by gcc with -fpatchable-function-entry option enabled. The
+ * same issue with kernel module. The retprobe doesn`t need debuginfo.
+ * This workaround solution use map to query the probe function address
+ * for retprobe event.
+ */
+ if (pev->point.retprobe)
+ return 0;
+
dinfo = open_debuginfo(pev->target, pev->nsi, !need_dwarf);
if (!dinfo) {
if (need_dwarf)
--
2.25.1
On Tue, 16 Feb 2021 18:30:26 +0800
Jianlin Lv <[email protected]> wrote:
> Perf failed to add kretprobe event with debuginfo of vmlinux which is
> compiled by gcc with -fpatchable-function-entry option enabled.
> The same issue with kernel module.
>
> Issue:
>
> # perf probe -v 'kernel_clone%return $retval'
> ......
> Writing event: r:probe/kernel_clone__return _text+599624 $retval
> Failed to write event: Invalid argument
> Error: Failed to add events. Reason: Invalid argument (Code: -22)
>
> # cat /sys/kernel/debug/tracing/error_log
> [156.75] trace_kprobe: error: Retprobe address must be an function entry
> Command: r:probe/kernel_clone__return _text+599624 $retval
> ^
>
> # llvm-dwarfdump vmlinux |grep -A 10 -w 0x00df2c2b
> 0x00df2c2b: DW_TAG_subprogram
> DW_AT_external (true)
> DW_AT_name ("kernel_clone")
> DW_AT_decl_file ("/home/code/linux-next/kernel/fork.c")
> DW_AT_decl_line (2423)
> DW_AT_decl_column (0x07)
> DW_AT_prototyped (true)
> DW_AT_type (0x00dcd492 "pid_t")
> DW_AT_low_pc (0xffff800010092648)
> DW_AT_high_pc (0xffff800010092b9c)
> DW_AT_frame_base (DW_OP_call_frame_cfa)
>
> # cat /proc/kallsyms |grep kernel_clone
> ffff800010092640 T kernel_clone
> # readelf -s vmlinux |grep -i kernel_clone
> 183173: ffff800010092640 1372 FUNC GLOBAL DEFAULT 2 kernel_clone
>
> # objdump -d vmlinux |grep -A 10 -w \<kernel_clone\>:
> ffff800010092640 <kernel_clone>:
> ffff800010092640: d503201f nop
> ffff800010092644: d503201f nop
> ffff800010092648: d503233f paciasp
> ffff80001009264c: a9b87bfd stp x29, x30, [sp, #-128]!
> ffff800010092650: 910003fd mov x29, sp
> ffff800010092654: a90153f3 stp x19, x20, [sp, #16]
>
> The entry address of kernel_clone converted by debuginfo is _text+599624
> (0x92648), which is consistent with the value of DW_AT_low_pc attribute.
> But the symbolic address of kernel_clone from /proc/kallsyms is
> ffff800010092640.
>
> This issue is found on arm64, -fpatchable-function-entry=2 is enabled when
> CONFIG_DYNAMIC_FTRACE_WITH_REGS=y;
> Just as objdump displayed the assembler contents of kernel_clone,
> GCC generate 2 NOPs at the beginning of each function.
>
> kprobe_on_func_entry detects that (_text+599624) is not the entry address
> of the function, which leads to the failure of adding kretprobe event.
>
> kprobe_on_func_entry
> ->_kprobe_addr
> ->kallsyms_lookup_size_offset
> ->arch_kprobe_on_func_entry // FALSE
>
> The cause of the issue is that the first instruction in the compile unit
> indicated by DW_AT_low_pc does not include NOPs.
> This issue exists in all gcc versions that support
> -fpatchable-function-entry option.
>
> I have reported it to the GCC community:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98776
>
> Currently arm64 and PA-RISC may enable fpatchable-function-entry option.
> The kernel compiled with clang does not have this issue.
>
> FIX:
>
> This GCC issue only cause the registration failure of the kretprobe event
> which doesn't need debuginfo. So, stop using debuginfo for retprobe.
> map will be used to query the probe function address.
>
> Signed-off-by: Jianlin Lv <[email protected]>
Looks good to me.
Acked-by: Masami Hiramatsu <[email protected]>
Thank you!
> ---
> v2: stop using debuginfo for retprobe, and update changelog.
> v3: Update changelog, fixed misuse of --- marker.
> ---
> tools/perf/util/probe-event.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 8eae2afff71a..a59d3268adb0 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -894,6 +894,16 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
> struct debuginfo *dinfo;
> int ntevs, ret = 0;
>
> + /* Workaround for gcc #98776 issue.
> + * Perf failed to add kretprobe event with debuginfo of vmlinux which is
> + * compiled by gcc with -fpatchable-function-entry option enabled. The
> + * same issue with kernel module. The retprobe doesn`t need debuginfo.
> + * This workaround solution use map to query the probe function address
> + * for retprobe event.
> + */
> + if (pev->point.retprobe)
> + return 0;
> +
> dinfo = open_debuginfo(pev->target, pev->nsi, !need_dwarf);
> if (!dinfo) {
> if (need_dwarf)
> --
> 2.25.1
>
--
Masami Hiramatsu <[email protected]>
On Tue, Feb 16, 2021 at 2:30 AM Jianlin Lv <[email protected]> wrote:
>
> Perf failed to add kretprobe event with debuginfo of vmlinux which is
> compiled by gcc with -fpatchable-function-entry option enabled.
> The same issue with kernel module.
>
> Issue:
>
> # perf probe -v 'kernel_clone%return $retval'
> ......
> Writing event: r:probe/kernel_clone__return _text+599624 $retval
> Failed to write event: Invalid argument
> Error: Failed to add events. Reason: Invalid argument (Code: -22)
>
> # cat /sys/kernel/debug/tracing/error_log
> [156.75] trace_kprobe: error: Retprobe address must be an function entry
> Command: r:probe/kernel_clone__return _text+599624 $retval
> ^
>
> # llvm-dwarfdump vmlinux |grep -A 10 -w 0x00df2c2b
> 0x00df2c2b: DW_TAG_subprogram
> DW_AT_external (true)
> DW_AT_name ("kernel_clone")
> DW_AT_decl_file ("/home/code/linux-next/kernel/fork.c")
> DW_AT_decl_line (2423)
> DW_AT_decl_column (0x07)
> DW_AT_prototyped (true)
> DW_AT_type (0x00dcd492 "pid_t")
> DW_AT_low_pc (0xffff800010092648)
> DW_AT_high_pc (0xffff800010092b9c)
> DW_AT_frame_base (DW_OP_call_frame_cfa)
>
> # cat /proc/kallsyms |grep kernel_clone
> ffff800010092640 T kernel_clone
> # readelf -s vmlinux |grep -i kernel_clone
> 183173: ffff800010092640 1372 FUNC GLOBAL DEFAULT 2 kernel_clone
>
> # objdump -d vmlinux |grep -A 10 -w \<kernel_clone\>:
> ffff800010092640 <kernel_clone>:
> ffff800010092640: d503201f nop
> ffff800010092644: d503201f nop
> ffff800010092648: d503233f paciasp
> ffff80001009264c: a9b87bfd stp x29, x30, [sp, #-128]!
> ffff800010092650: 910003fd mov x29, sp
> ffff800010092654: a90153f3 stp x19, x20, [sp, #16]
>
> The entry address of kernel_clone converted by debuginfo is _text+599624
> (0x92648), which is consistent with the value of DW_AT_low_pc attribute.
> But the symbolic address of kernel_clone from /proc/kallsyms is
> ffff800010092640.
>
> This issue is found on arm64, -fpatchable-function-entry=2 is enabled when
> CONFIG_DYNAMIC_FTRACE_WITH_REGS=y;
> Just as objdump displayed the assembler contents of kernel_clone,
> GCC generate 2 NOPs at the beginning of each function.
>
> kprobe_on_func_entry detects that (_text+599624) is not the entry address
> of the function, which leads to the failure of adding kretprobe event.
>
> kprobe_on_func_entry
> ->_kprobe_addr
> ->kallsyms_lookup_size_offset
> ->arch_kprobe_on_func_entry // FALSE
>
> The cause of the issue is that the first instruction in the compile unit
> indicated by DW_AT_low_pc does not include NOPs.
> This issue exists in all gcc versions that support
> -fpatchable-function-entry option.
>
> I have reported it to the GCC community:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98776
>
> Currently arm64 and PA-RISC may enable fpatchable-function-entry option.
> The kernel compiled with clang does not have this issue.
Thank you for taking the time to check and verify with Clang. I appreciate it!
>
> FIX:
>
> This GCC issue only cause the registration failure of the kretprobe event
> which doesn't need debuginfo. So, stop using debuginfo for retprobe.
> map will be used to query the probe function address.
>
> Signed-off-by: Jianlin Lv <[email protected]>
> ---
> v2: stop using debuginfo for retprobe, and update changelog.
> v3: Update changelog, fixed misuse of --- marker.
> ---
> tools/perf/util/probe-event.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 8eae2afff71a..a59d3268adb0 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -894,6 +894,16 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
> struct debuginfo *dinfo;
> int ntevs, ret = 0;
>
> + /* Workaround for gcc #98776 issue.
> + * Perf failed to add kretprobe event with debuginfo of vmlinux which is
> + * compiled by gcc with -fpatchable-function-entry option enabled. The
> + * same issue with kernel module. The retprobe doesn`t need debuginfo.
> + * This workaround solution use map to query the probe function address
> + * for retprobe event.
> + */
> + if (pev->point.retprobe)
> + return 0;
> +
> dinfo = open_debuginfo(pev->target, pev->nsi, !need_dwarf);
> if (!dinfo) {
> if (need_dwarf)
> --
> 2.25.1
>
--
Thanks,
~Nick Desaulniers