[PATCH] perf test: probe_vfs_getname add do_getname() probing fallback

[PATCH] perf test: probe_vfs_getname add do_getname() probing fallback

[Thomas Richter]

The following tests are skipped for some time now on platforms
s390 and x86_64:

 # perf test vfs_getname
 138: Add vfs_getname probe to get syscall args filenames    : Skip
 140: Use vfs_getname probe to get syscall args filenames    : Skip
 154: Check open filename arg using perf trace + vfs_getname : Skip
 #

This is caused by a change in kernel code of function
getname_flags(), see
  commit 9fa3ec84587c ("allow incomplete imports of filenames")
This commit changed the function getname_flags() implementation.

Now the perf probe 'vfs_getname parameter=xxx' does not match any
more. Extend the test logic to fall back to probing do_getname().
This reflects the updated kernel code.

Output after:
 # perf test vfs_getname
 138: Add vfs_getname probe to get syscall args filenames    : Ok
 140: Use vfs_getname probe to get syscall args filenames    : Ok
 154: Check open filename arg using perf trace + vfs_getname : Ok
 #

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
---
 tools/perf/tests/shell/lib/probe_vfs_getname.sh | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
index 88cd0e26d5f6..9156a79212b9 100644
--- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
+++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
@@ -12,6 +12,8 @@ cleanup_probe_vfs_getname() {
 
 add_probe_vfs_getname() {
 	add_probe_verbose=$1
+	do_getname=0
+
 	if [ $had_vfs_getname -eq 1 ] ; then
 		result_initname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+initname.*"
 		line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_initname_re" | sed -r "s/$result_initname_re/\1/")
@@ -28,12 +30,24 @@ add_probe_vfs_getname() {
 			line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_aname_re" | sed -r "s/$result_aname_re/\1/")
 		fi
 
+		if [ -z "$line" ] ; then
+			do_getname=1
+			result_iname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+initname\(result\);"
+			line=$(perf probe -L do_getname 2>&1 | grep -E "$result_iname_re" | sed -r "s/$result_iname_re/\1/")
+		fi
+
 		if [ -z "$line" ] ; then
 			echo "Could not find probeable line"
 			return 2
 		fi
 
-		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
+		if [ "$do_getname" -eq 1 ]
+		then
+			param="vfs_getname=do_getname:${line} pathname=result->iname:string"
+			perf probe -q "$param" || perf probe $add_probe_verbose "$param" || return 1
+			return 0
+		fi
+		perf probe -q "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
 		perf probe $add_probe_verbose "vfs_getname=getname_flags:${line} pathname=filename:ustring" || return 1
 	fi
 }
-- 
2.53.0

[PATCH Ping] perf test: probe_vfs_getname add do_getname() probing fallback

[Thomas Richter]

Friendly ping...

On 4/16/26 14:55, Thomas Richter wrote:
> The following tests are skipped for some time now on platforms
> s390 and x86_64:
> 
>  # perf test vfs_getname
>  138: Add vfs_getname probe to get syscall args filenames    : Skip
>  140: Use vfs_getname probe to get syscall args filenames    : Skip
>  154: Check open filename arg using perf trace + vfs_getname : Skip
>  #
> 
> This is caused by a change in kernel code of function
> getname_flags(), see
>   commit 9fa3ec84587c ("allow incomplete imports of filenames")
> This commit changed the function getname_flags() implementation.
> 
> Now the perf probe 'vfs_getname parameter=xxx' does not match any
> more. Extend the test logic to fall back to probing do_getname().
> This reflects the updated kernel code.
> 
> Output after:
>  # perf test vfs_getname
>  138: Add vfs_getname probe to get syscall args filenames    : Ok
>  140: Use vfs_getname probe to get syscall args filenames    : Ok
>  154: Check open filename arg using perf trace + vfs_getname : Ok
>  #
> 
> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
> Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
> ---
>  tools/perf/tests/shell/lib/probe_vfs_getname.sh | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> index 88cd0e26d5f6..9156a79212b9 100644
> --- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> +++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> @@ -12,6 +12,8 @@ cleanup_probe_vfs_getname() {
>  
>  add_probe_vfs_getname() {
>  	add_probe_verbose=$1
> +	do_getname=0
> +
>  	if [ $had_vfs_getname -eq 1 ] ; then
>  		result_initname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+initname.*"
>  		line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_initname_re" | sed -r "s/$result_initname_re/\1/")
> @@ -28,12 +30,24 @@ add_probe_vfs_getname() {
>  			line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_aname_re" | sed -r "s/$result_aname_re/\1/")
>  		fi
>  
> +		if [ -z "$line" ] ; then
> +			do_getname=1
> +			result_iname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+initname\(result\);"
> +			line=$(perf probe -L do_getname 2>&1 | grep -E "$result_iname_re" | sed -r "s/$result_iname_re/\1/")
> +		fi
> +
>  		if [ -z "$line" ] ; then
>  			echo "Could not find probeable line"
>  			return 2
>  		fi
>  
> -		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
> +		if [ "$do_getname" -eq 1 ]
> +		then
> +			param="vfs_getname=do_getname:${line} pathname=result->iname:string"
> +			perf probe -q "$param" || perf probe $add_probe_verbose "$param" || return 1
> +			return 0
> +		fi
> +		perf probe -q "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
>  		perf probe $add_probe_verbose "vfs_getname=getname_flags:${line} pathname=filename:ustring" || return 1
>  	fi
>  }


-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH

Vorsitzender des Aufsichtsrats: Wolfgang Wendt

Geschäftsführung: David Faller

Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

Re: [PATCH] perf test: probe_vfs_getname add do_getname() probing fallback

[sashiko-bot]

Sashiko AI review found 2 potential issue(s):
- [Medium] Out-of-bounds kernel memory read in `do_getname` perf probe due to unterminated string.
- [Medium] Missing user-space pointer fallback logic reduces test robustness.
--

commit 44caa018a80d8e3283b4eda7b6e0f0690afbe123
Author: Thomas Richter <tmricht@linux.ibm.com>

perf test: probe_vfs_getname add do_getname() probing fallback

This commit extends the vfs_getname perf test logic to fall back to probing
do_getname() if getname_flags() does not match. This reflects updated kernel
code where the getname_flags() implementation was changed.

> diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> --- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> +++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
[ ... ]
> @@ -28,12 +30,24 @@ add_probe_vfs_getname() {
>  			line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_aname_re" | sed -r "s/$result_aname_re/\1/")
>  		fi
>  
> +		if [ -z "$line" ] ; then
> +			do_getname=1
> +			result_iname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+initname\(result\);"
> +			line=$(perf probe -L do_getname 2>&1 | grep -E "$result_iname_re" | sed -r "s/$result_iname_re/\1/")
> +		fi
> +
>  		if [ -z "$line" ] ; then
>  			echo "Could not find probeable line"
>  			return 2
>  		fi
>  
> -		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
> +		if [ "$do_getname" -eq 1 ]
> +		then
> +			param="vfs_getname=do_getname:${line} pathname=result->iname:string"

Does this probe cause an out-of-bounds kernel memory read when the path exceeds
EMBEDDED_NAME_MAX?

If a user provides a long file path, strncpy_from_user() completely fills the
fixed-size result->iname array without appending a NUL terminator, while the
actual NUL-terminated path is dynamically allocated and pointed to by
result->name.

Because the probe explicitly instructs the kernel to read result->iname as a
NUL-terminated string, could the kprobe fetcher read past the end of the iname
array into adjacent slab memory? Should this use result->name:string instead?

> +			perf probe -q "$param" || perf probe $add_probe_verbose "$param" || return 1

Is the user-space pointer fallback missing here?

The original probe logic for getname_flags robustly handles compiler
optimizations by falling back to probing the user-space function argument
directly (pathname=filename:ustring) if reading the kernel result struct fails.

This new block for do_getname instead retries the exact same probe string, just
adding a verbose flag. Since filename remains the first argument to
do_getname(), would it be safer to include the filename:ustring fallback to
prevent the test from failing on certain toolchains?

> +			return 0
> +		fi
> +		perf probe -q "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
>  		perf probe $add_probe_verbose "vfs_getname=getname_flags:${line} pathname=filename:ustring" || return 1
>  	fi
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260416125515.3481495-1-tmricht@linux.ibm.com?part=1