mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
synced 2025-01-07 14:32:23 +00:00
c8e57ab099
In the current code, gdb can set the watchpoint successfully through
ptrace interface, but watchpoint will not be triggered.
When debugging the following code using gdb.
lihui@bogon:~$ cat test.c
#include <stdio.h>
int a = 0;
int main()
{
a = 1;
printf("a = %d\n", a);
return 0;
}
lihui@bogon:~$ gcc -g test.c -o test
lihui@bogon:~$ gdb test
...
(gdb) watch a
...
(gdb) r
...
a = 1
[Inferior 1 (process 4650) exited normally]
No watchpoints were triggered, the root causes are:
1. Kernel uses perf_event and hw_breakpoint framework to control
watchpoint, but the perf_event corresponding to watchpoint is
not enabled. So it needs to be enabled according to MWPnCFG3
or FWPnCFG3 PLV bit field in ptrace_hbp_set_ctrl(), and privilege
is set according to the monitored addr in hw_breakpoint_control().
Furthermore, add a judgment in ptrace_hbp_set_addr() to ensure
kernel-space addr cannot be monitored in user mode.
2. The global enable control for all watchpoints is the WE bit of
CSR.CRMD, and hardware sets the value to 0 when an exception is
triggered. When the ERTN instruction is executed to return, the
hardware restores the value of the PWE field of CSR.PRMD here.
So, before a thread containing watchpoints be scheduled, the PWE
field of CSR.PRMD needs to be set to 1. Add this modification in
hw_breakpoint_control().
All changes according to the LoongArch Reference Manual:
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#basic-control-and-status-registers
With this patch:
lihui@bogon:~$ gdb test
...
(gdb) watch a
Hardware watchpoint 1: a
(gdb) r
...
Hardware watchpoint 1: a
Old value = 0
New value = 1
main () at test.c:6
6 printf("a = %d\n", a);
(gdb) c
Continuing.
a = 1
[Inferior 1 (process 775) exited normally]
Cc: stable@vger.kernel.org
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
|
||
|---|---|---|
| .. | ||
| boot | ||
| configs | ||
| crypto | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mm | ||
| net | ||
| pci | ||
| power | ||
| vdso | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||