[PATCH v2] perf probe: fix kretprobe issue caused by GCC bug

[PATCH v2] perf probe: fix kretprobe issue caused by GCC bug

[Jianlin Lv]

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 <Jianlin.Lv@arm.com>
---
v2: stop using debuginfo for retprobe, and update changelog.
---
 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

Re: [PATCH v2] perf probe: fix kretprobe issue caused by GCC bug

[Masami Hiramatsu]

On Wed, 10 Feb 2021 14:26:46 +0800
Jianlin Lv <Jianlin.Lv@arm.com> 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.

Looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thanks!

> 
> Signed-off-by: Jianlin Lv <Jianlin.Lv@arm.com>
> ---
> v2: stop using debuginfo for retprobe, and update changelog.
> ---
>  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 <mhiramat@kernel.org>

Re: [PATCH v2] perf probe: fix kretprobe issue caused by GCC bug

[Arnaldo Carvalho de Melo]

Em Wed, Feb 10, 2021 at 02:26:46PM +0800, Jianlin Lv escreveu:
> 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
> ---

Please don't use --- at the start of a line, it is used to separate from
the patch itself, later down your message.

It causes this:

[acme@five perf]$ am /wb/1.patch
Traceback (most recent call last):
  File "/home/acme/bin/ksoff.py", line 180, in <module>
    sign_msg(sys.stdin, sys.stdout)
  File "/home/acme/bin/ksoff.py", line 142, in sign_msg
    sob.remove(last_sob[0])
TypeError: 'NoneType' object is not subscriptable
[acme@five perf]$

I'm fixing this by removing that --- markers
 
> 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 <Jianlin.Lv@arm.com>
> ---
> v2: stop using debuginfo for retprobe, and update changelog.
> ---
>  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
> 

-- 

- Arnaldo

RE: [PATCH v2] perf probe: fix kretprobe issue caused by GCC bug

[Jianlin Lv]

> -----Original Message-----
> From: Arnaldo Carvalho de Melo <acme@kernel.org>
> Sent: Saturday, February 13, 2021 5:34 AM
> To: Jianlin Lv <Jianlin.Lv@arm.com>
> Cc: peterz@infradead.org; mingo@redhat.com; Mark Rutland
> <Mark.Rutland@arm.com>; alexander.shishkin@linux.intel.com;
> jolsa@redhat.com; namhyung@kernel.org; nathan@kernel.org;
> ndesaulniers@google.com; mhiramat@kernel.org; fche@redhat.com;
> irogers@google.com; sumanthk@linux.ibm.com; linux-
> kernel@vger.kernel.org; clang-built-linux@googlegroups.com
> Subject: Re: [PATCH v2] perf probe: fix kretprobe issue caused by GCC bug
>
> Em Wed, Feb 10, 2021 at 02:26:46PM +0800, Jianlin Lv escreveu:
> > 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
> > ---
>
> Please don't use --- at the start of a line, it is used to separate from the patch
> itself, later down your message.
>
> It causes this:
>
> [acme@five perf]$ am /wb/1.patch
> Traceback (most recent call last):
>   File "/home/acme/bin/ksoff.py", line 180, in <module>
>     sign_msg(sys.stdin, sys.stdout)
>   File "/home/acme/bin/ksoff.py", line 142, in sign_msg
>     sob.remove(last_sob[0])
> TypeError: 'NoneType' object is not subscriptable [acme@five perf]$
>
> I'm fixing this by removing that --- markers
>

Sorry for the inconvenience?
Should I commit another version to fix this issue?

Jianlin

> > 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 <Jianlin.Lv@arm.com>
> > ---
> > v2: stop using debuginfo for retprobe, and update changelog.
> > ---
> >  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
> >
>
> --
>
> - Arnaldo
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