2012-11-05 22:49:21

by Hannes Frederic Sowa

Subject: [PATCH] [perf] convert_variable_type does not correctly check type of arrays

While casting an array of (unsigned) chars to a string, perf does not
check the containing type but only the opaque type and is bailing out:

$ perf probe -v -a 'neigh_destroy:22 dev->name:string'
probe-definition(0): neigh_destroy:22 dev->name:string
symbol:neigh_destroy file:(null) line:22 offset:0 return:0 lazy:(null)
parsing arg: dev->name:string into type:string dev, name(1)
1 arguments
Use vmlinux: /home/hannes/linux/vmlinux
Using /home/hannes/linux/vmlinux for symbols
Probe point found: neigh_destroy+115
Searching 'dev' variable in context.
Converting variable dev into trace event.
converting name in dev
name type is (null).
Failed to cast into string: name is not (unsigned) char *.
Failed to find 'dev' in this function.
An error occurred in debuginfo analysis (-22).
Error: Failed to add events. (-22)

After the code flow ensures that type could only be a pointer or
array type, call die_get_real_type unconditionally again to fetch the
containing type and have further validation been done on that Die.

Cc: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Hannes Frederic Sowa <[email protected]>
---
tools/perf/util/probe-finder.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 1daf5c1..2a61ea5 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -413,12 +413,13 @@ static int convert_variable_type(Dwarf_Die *vr_die,
dwarf_diename(vr_die), dwarf_diename(&type));
return -EINVAL;
}
+ if (die_get_real_type(&type, &type) == NULL) {
+ pr_warning("Failed to get a type information.\n");
+ return -ENOENT;
+ }
+ pr_debug("containing type of %s is %s.\n",
+ dwarf_diename(vr_die), dwarf_diename(&type));
if (ret == DW_TAG_pointer_type) {
- if (die_get_real_type(&type, &type) == NULL) {
- pr_warning("Failed to get a type"
- " information.\n");
- return -ENOENT;
- }
while (*ref_ptr)
ref_ptr = &(*ref_ptr)->next;
/* Add new reference with offset +0 */

2012-11-07 07:46:35

by Namhyung Kim

Subject: Re: [PATCH] [perf] convert_variable_type does not correctly check type of arrays

Hi Hannes,

On Mon, 5 Nov 2012 23:49:16 +0100, Hannes Frederic Sowa wrote:
> While casting an array of (unsigned) chars to a string, perf does not
> check the containing type but only the opaque type and is bailing out:
>
> $ perf probe -v -a 'neigh_destroy:22 dev->name:string'
> probe-definition(0): neigh_destroy:22 dev->name:string
> symbol:neigh_destroy file:(null) line:22 offset:0 return:0 lazy:(null)
> parsing arg: dev->name:string into type:string dev, name(1)
> 1 arguments
> Use vmlinux: /home/hannes/linux/vmlinux
> Using /home/hannes/linux/vmlinux for symbols
> Probe point found: neigh_destroy+115
> Searching 'dev' variable in context.
> Converting variable dev into trace event.
> converting name in dev
> name type is (null).
> Failed to cast into string: name is not (unsigned) char *.
> Failed to find 'dev' in this function.
> An error occurred in debuginfo analysis (-22).
> Error: Failed to add events. (-22)
>
> After the code flow ensures that type could only be a pointer or
> array type, call die_get_real_type unconditionally again to fetch the
> containing type and have further validation been done on that Die.

Hyeoncheol posted a same fix before, but not merged yet, Arnaldo?

https://lkml.org/lkml/2012/9/20/3

Thanks,
Namhyung