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author | Li Huafei <lihuafei1@huawei.com> | 2021-06-01 12:27:50 +0300 |
---|---|---|
committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2021-06-01 16:11:24 +0300 |
commit | 3cb17cce1e76ccc5499915a4d7e095a1ad6bf7ff (patch) | |
tree | c29bce58c7dfa286185d854f9d7e6d98122d37d7 /tools/perf/util | |
parent | 6c1ced2f701618e912be6c549139d58c180419ea (diff) | |
download | linux-3cb17cce1e76ccc5499915a4d7e095a1ad6bf7ff.tar.xz |
perf probe: Fix NULL pointer dereference in convert_variable_location()
If we just check whether the variable can be converted, 'tvar' should be
a null pointer. However, the null pointer check is missing in the
'Constant value' execution path.
The following cases can trigger this problem:
$ cat test.c
#include <stdio.h>
void main(void)
{
int a;
const int b = 1;
asm volatile("mov %1, %0" : "=r"(a): "i"(b));
printf("a: %d\n", a);
}
$ gcc test.c -o test -O -g
$ sudo ./perf probe -x ./test -L "main"
<main@/home/lhf/test.c:0>
0 void main(void)
{
2 int a;
const int b = 1;
asm volatile("mov %1, %0" : "=r"(a): "i"(b));
6 printf("a: %d\n", a);
}
$ sudo ./perf probe -x ./test -V "main:6"
Segmentation fault
The check on 'tvar' is added. If 'tavr' is a null pointer, we return 0
to indicate that the variable can be converted. Now, we can successfully
show the variables that can be accessed.
$ sudo ./perf probe -x ./test -V "main:6"
Available variables at main:6
@<main+13>
char* __fmt
int a
int b
However, the variable 'b' cannot be tracked.
$ sudo ./perf probe -x ./test -D "main:6 b"
Failed to find the location of the 'b' variable at this address.
Perhaps it has been optimized out.
Use -V with the --range option to show 'b' location range.
Error: Failed to add events.
This is because __die_find_variable_cb() did not successfully match
variable 'b', which has the DW_AT_const_value attribute instead of
DW_AT_location. We added support for DW_AT_const_value in
__die_find_variable_cb(). With this modification, we can successfully
track the variable 'b'.
$ sudo ./perf probe -x ./test -D "main:6 b"
p:probe_test/main_L6 /home/lhf/test:0x1156 b=\1:s32
Fixes: 66f69b219716 ("perf probe: Support DW_AT_const_value constant value")
Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Jianlin Lv <jianlin.lv@arm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Zhang Jinhao <zhangjinhao2@huawei.com>
http://lore.kernel.org/lkml/20210601092750.169601-1-lihuafei1@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util')
-rw-r--r-- | tools/perf/util/dwarf-aux.c | 8 | ||||
-rw-r--r-- | tools/perf/util/probe-finder.c | 3 |
2 files changed, 9 insertions, 2 deletions
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index b2f4920e19a6..7d2ba8419b0c 100644 --- a/tools/perf/util/dwarf-aux.c +++ b/tools/perf/util/dwarf-aux.c @@ -975,9 +975,13 @@ static int __die_find_variable_cb(Dwarf_Die *die_mem, void *data) if ((tag == DW_TAG_formal_parameter || tag == DW_TAG_variable) && die_compare_name(die_mem, fvp->name) && - /* Does the DIE have location information or external instance? */ + /* + * Does the DIE have location information or const value + * or external instance? + */ (dwarf_attr(die_mem, DW_AT_external, &attr) || - dwarf_attr(die_mem, DW_AT_location, &attr))) + dwarf_attr(die_mem, DW_AT_location, &attr) || + dwarf_attr(die_mem, DW_AT_const_value, &attr))) return DIE_FIND_CB_END; if (dwarf_haspc(die_mem, fvp->addr)) return DIE_FIND_CB_CONTINUE; diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c index 866f2d514d72..b029c29ce227 100644 --- a/tools/perf/util/probe-finder.c +++ b/tools/perf/util/probe-finder.c @@ -190,6 +190,9 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr, immediate_value_is_supported()) { Dwarf_Sword snum; + if (!tvar) + return 0; + dwarf_formsdata(&attr, &snum); ret = asprintf(&tvar->value, "\\%ld", (long)snum); |