forked from luck/tmp_suning_uos_patched
091283e3d5
[ Upstream commit 3cb17cce1e76ccc5499915a4d7e095a1ad6bf7ff ]
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:
|
||
---|---|---|
.. | ||
accounting | ||
arch | ||
bootconfig | ||
bpf | ||
build | ||
cgroup | ||
debugging | ||
edid | ||
firewire | ||
firmware | ||
gpio | ||
hv | ||
iio | ||
include | ||
io_uring | ||
kvm/kvm_stat | ||
laptop | ||
leds | ||
lib | ||
memory-model | ||
objtool | ||
pci | ||
pcmcia | ||
perf | ||
power | ||
scripts | ||
spi | ||
testing | ||
thermal/tmon | ||
time | ||
usb | ||
virtio | ||
vm | ||
wmi | ||
Makefile |