From: Hui Li <lihui@xxxxxxxxxxx>
commit 3eb2a8b23598e90fda43abb0f23cb267bd5018ba upstream.
In the current code, if multiple hardware breakpoints/watchpoints in
a user-space thread, some of them will not be triggered.
When debugging the following code using gdb.
lihui@bogon:~$ cat test.c
#include <stdio.h>
int a = 0;
int main()
{
printf("start test\n");
a = 1;
printf("a = %d\n", a);
printf("end test\n");
return 0;
}
lihui@bogon:~$ gcc -g test.c -o test
lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5 printf("start test\n");
(gdb) watch a
Hardware watchpoint 2: a
(gdb) hbreak 8
Hardware assisted breakpoint 3 at 0x1200006ec: file test.c, line 8.
(gdb) c
Continuing.
start test
a = 1
Breakpoint 3, main () at test.c:8
8 printf("end test\n");
...
The first hardware watchpoint is not triggered, the root causes are:
1. In hw_breakpoint_control(), The FWPnCFG1.2.4/MWPnCFG1.2.4 register
settings are not distinguished. They should be set based on hardware
watchpoint functions (fetch or load/store operations).
2. In breakpoint_handler() and watchpoint_handler(), it doesn't identify
which watchpoint is triggered. So, all watchpoint-related perf_event
callbacks are called and siginfo is sent to the user space. This will
cause user-space unable to determine which watchpoint is triggered.
The kernel need to identity which watchpoint is triggered via MWPS/
FWPS registers, and then call the corresponding perf event callbacks
to report siginfo to the user-space.
Modify the relevant code to solve above issues.
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
With this patch:
lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5 printf("start test\n");
(gdb) watch a
Hardware watchpoint 2: a
(gdb) hbreak 8
Hardware assisted breakpoint 3 at 0x1200006ec: file test.c, line 8.
(gdb) c
Continuing.
start test
Hardware watchpoint 2: a
Old value = 0
New value = 1
main () at test.c:7
7 printf("a = %d\n", a);
(gdb) c
Continuing.
a = 1
Breakpoint 3, main () at test.c:8
8 printf("end test\n");
(gdb) c
Continuing.
end test
[Inferior 1 (process 778) exited normally]
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hui Li <lihui@xxxxxxxxxxx>
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/loongarch/kernel/hw_breakpoint.c | 57 +++++++++++++++++++---------------
1 file changed, 33 insertions(+), 24 deletions(-)
--- a/arch/loongarch/kernel/hw_breakpoint.c
+++ b/arch/loongarch/kernel/hw_breakpoint.c
@@ -207,15 +207,15 @@ static int hw_breakpoint_control(struct
switch (ops) {
case HW_BREAKPOINT_INSTALL:
/* Set the FWPnCFG/MWPnCFG 1~4 register. */
- write_wb_reg(CSR_CFG_ADDR, i, 0, info->address);
- write_wb_reg(CSR_CFG_ADDR, i, 1, info->address);
- write_wb_reg(CSR_CFG_MASK, i, 0, info->mask);
- write_wb_reg(CSR_CFG_MASK, i, 1, info->mask);
- write_wb_reg(CSR_CFG_ASID, i, 0, 0);
- write_wb_reg(CSR_CFG_ASID, i, 1, 0);
if (info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) {
+ write_wb_reg(CSR_CFG_ADDR, i, 0, info->address);
+ write_wb_reg(CSR_CFG_MASK, i, 0, info->mask);
+ write_wb_reg(CSR_CFG_ASID, i, 0, 0);
write_wb_reg(CSR_CFG_CTRL, i, 0, privilege);
} else {
+ write_wb_reg(CSR_CFG_ADDR, i, 1, info->address);
+ write_wb_reg(CSR_CFG_MASK, i, 1, info->mask);
+ write_wb_reg(CSR_CFG_ASID, i, 1, 0);
ctrl = encode_ctrl_reg(info->ctrl);
write_wb_reg(CSR_CFG_CTRL, i, 1, ctrl | privilege);
}
@@ -226,14 +226,17 @@ static int hw_breakpoint_control(struct
break;
case HW_BREAKPOINT_UNINSTALL:
/* Reset the FWPnCFG/MWPnCFG 1~4 register. */
- write_wb_reg(CSR_CFG_ADDR, i, 0, 0);
- write_wb_reg(CSR_CFG_ADDR, i, 1, 0);
- write_wb_reg(CSR_CFG_MASK, i, 0, 0);
- write_wb_reg(CSR_CFG_MASK, i, 1, 0);
- write_wb_reg(CSR_CFG_CTRL, i, 0, 0);
- write_wb_reg(CSR_CFG_CTRL, i, 1, 0);
- write_wb_reg(CSR_CFG_ASID, i, 0, 0);
- write_wb_reg(CSR_CFG_ASID, i, 1, 0);
+ if (info->ctrl.type == LOONGARCH_BREAKPOINT_EXECUTE) {
+ write_wb_reg(CSR_CFG_ADDR, i, 0, 0);
+ write_wb_reg(CSR_CFG_MASK, i, 0, 0);
+ write_wb_reg(CSR_CFG_CTRL, i, 0, 0);
+ write_wb_reg(CSR_CFG_ASID, i, 0, 0);
+ } else {
+ write_wb_reg(CSR_CFG_ADDR, i, 1, 0);
+ write_wb_reg(CSR_CFG_MASK, i, 1, 0);
+ write_wb_reg(CSR_CFG_CTRL, i, 1, 0);
+ write_wb_reg(CSR_CFG_ASID, i, 1, 0);
+ }
if (bp->hw.target)
regs->csr_prmd &= ~CSR_PRMD_PWE;
break;
@@ -476,12 +479,15 @@ void breakpoint_handler(struct pt_regs *
slots = this_cpu_ptr(bp_on_reg);
for (i = 0; i < boot_cpu_data.watch_ireg_count; ++i) {
- bp = slots[i];
- if (bp == NULL)
- continue;
- perf_bp_event(bp, regs);
+ if ((csr_read32(LOONGARCH_CSR_FWPS) & (0x1 << i))) {
+ bp = slots[i];
+ if (bp == NULL)
+ continue;
+ perf_bp_event(bp, regs);
+ csr_write32(0x1 << i, LOONGARCH_CSR_FWPS);
+ update_bp_registers(regs, 0, 0);
+ }
}
- update_bp_registers(regs, 0, 0);
}
NOKPROBE_SYMBOL(breakpoint_handler);
@@ -493,12 +499,15 @@ void watchpoint_handler(struct pt_regs *
slots = this_cpu_ptr(wp_on_reg);
for (i = 0; i < boot_cpu_data.watch_dreg_count; ++i) {
- wp = slots[i];
- if (wp == NULL)
- continue;
- perf_bp_event(wp, regs);
+ if ((csr_read32(LOONGARCH_CSR_MWPS) & (0x1 << i))) {
+ wp = slots[i];
+ if (wp == NULL)
+ continue;
+ perf_bp_event(wp, regs);
+ csr_write32(0x1 << i, LOONGARCH_CSR_MWPS);
+ update_bp_registers(regs, 0, 1);
+ }
}
- update_bp_registers(regs, 0, 1);
}
NOKPROBE_SYMBOL(watchpoint_handler);
Patches currently in stable-queue which might be from lihui@xxxxxxxxxxx are
queue-6.9/loongarch-fix-watchpoint-setting-error.patch
queue-6.9/loongarch-trigger-user-space-watchpoints-correctly.patch
queue-6.9/loongarch-fix-multiple-hardware-watchpoint-issues.patch
