[PATCH v2] perf test: Fix test trace+probe_vfs_getname.sh

[PATCH v2] perf test: Fix test trace+probe_vfs_getname.sh

[Thomas Richter]

This test places a kprobe to function getname_flags() in the kernel
which has the following prototype:

  struct filename *
  getname_flags(const char __user *filename, int flags, int *empty)

Variable filename points to a filename located in user space memory.
Looking at
commit 88903c464321c ("tracing/probe: Add ustring type for user-space string")
the kprobe should indicate that user space memory is accessed.

Fix this with a patch to specify user space memory access to
parameter 'filename' and 'string' is replaced by 'ustring'.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/tests/shell/lib/probe_vfs_getname.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
index 7cb99b433888..7ecf117651dd 100644
--- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
+++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
@@ -13,8 +13,8 @@ add_probe_vfs_getname() {
 	local verbose=$1
 	if [ $had_vfs_getname -eq 1 ] ; then
 		line=$(perf probe -L getname_flags 2>&1 | egrep 'result.*=.*filename;' | sed -r 's/[[:space:]]+([[:digit:]]+)[[:space:]]+result->uptr.*/\1/')
-		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
-		perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:string"
+		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->uptr:ustring" || \
+		perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:ustring"
 	fi
 }
 
-- 
2.21.0

Re: [PATCH v2] perf test: Fix test trace+probe_vfs_getname.sh

[Arnaldo Carvalho de Melo]

Em Mon, Jan 20, 2020 at 02:20:11PM +0100, Thomas Richter escreveu:
> This test places a kprobe to function getname_flags() in the kernel
> which has the following prototype:
> 
>   struct filename *
>   getname_flags(const char __user *filename, int flags, int *empty)
> 
> Variable filename points to a filename located in user space memory.
> Looking at
> commit 88903c464321c ("tracing/probe: Add ustring type for user-space string")
> the kprobe should indicate that user space memory is accessed.

We can't just replace it, right? I.e. this should continue to work with
older kernels, i.e. the latest userspace tooling version should work
when installed in an older kernel, i.e. please just add more fallbacks
to cover the new cases.

- Arnaldo
 
> Fix this with a patch to specify user space memory access to
> parameter 'filename' and 'string' is replaced by 'ustring'.
> 
> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
> ---
>  tools/perf/tests/shell/lib/probe_vfs_getname.sh | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> index 7cb99b433888..7ecf117651dd 100644
> --- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> +++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> @@ -13,8 +13,8 @@ add_probe_vfs_getname() {
>  	local verbose=$1
>  	if [ $had_vfs_getname -eq 1 ] ; then
>  		line=$(perf probe -L getname_flags 2>&1 | egrep 'result.*=.*filename;' | sed -r 's/[[:space:]]+([[:digit:]]+)[[:space:]]+result->uptr.*/\1/')
> -		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
> -		perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:string"
> +		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->uptr:ustring" || \
> +		perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:ustring"
>  	fi
>  }
>  
> -- 
> 2.21.0
> 

-- 

- Arnaldo

[PATCH v2] perf test: Fix test trace+probe_vfs_getname.sh

[Thomas Richter]

This test places a kprobe to function getname_flags() in the kernel
which has the following prototype:

  struct filename *
  getname_flags(const char __user *filename, int flags, int *empty)

Variable filename points to a filename located in user space memory.
Looking at
commit 88903c464321c ("tracing/probe: Add ustring type for user-space string")
the kprobe should indicate that user space memory is accessed.

So I suggest the following patch to specify user space memory access.
Try type 'ustring' first and use type 'string' in case 'ustring'
is not supported.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/tests/shell/lib/probe_vfs_getname.sh | 4 +++-
 1 file changed, 3 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 7cb99b433888..30c1eadbc5be 100644
--- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
+++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
@@ -13,7 +13,9 @@ add_probe_vfs_getname() {
 	local verbose=$1
 	if [ $had_vfs_getname -eq 1 ] ; then
 		line=$(perf probe -L getname_flags 2>&1 | egrep 'result.*=.*filename;' | sed -r 's/[[:space:]]+([[:digit:]]+)[[:space:]]+result->uptr.*/\1/')
-		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
+		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->uptr:ustring" || \
+		perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:ustring" || \
+		perf probe -q       "vfs_getname=getname_flags:${line} pathname=result->uptr:string" || \
 		perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:string"
 	fi
 }
-- 
2.21.0