After the single-step exception handling oops is fixed, when we execute
single-step in kdb/kgdb, we may see it jumps to the irq_handler (where
PSTATE.D is cleared) instead of the next instruction.
Add the prepare and cleanup work for single-step when enabling and
disabling to maintain the PSTATE.I and PSTATE.D carefully.
Before this patch:
* kdb:
Entering kdb (current=0xffff8000119e2dc0, pid 0) on processor 0 due to Keyboard
Entry
[0]kdb> bp printk
Instruction(i) BP #0 at 0xffff8000101486cc (printk)
is enabled addr at ffff8000101486cc, hardtype=0 installed=0
[0]kdb> g
/ # echo h > /proc/sysrq-trigger
Entering kdb (current=0xffff0000fada65c0, pid 267) on processor 0 due to
Breakpoint @ 0xffff8000101486cc
[0]kdb> ss
Entering kdb (current=0xffff0000fada65c0, pid 267) on processor 0 due to SS
trap @ 0xffff800010082ab8
[0]kdb> 0xffff800010082ab8
0xffff800010082ab8 = 0xffff800010082ab8 (el1_irq+0x78)
[0]kdb>
0xffff800010082ab0 <+112>: nop
0xffff800010082ab4 <+116>: msr daifclr, #0xd
0xffff800010082ab8 <+120>: adrp x1, 0xffff8000113a7000 <cpu_ops+1288>
0xffff800010082abc <+124>: ldr x1, [x1, #1408]
* kgdb:
(gdb) target remote 127.1:23002
Remote debugging using 127.1:23002
arch_kgdb_breakpoint () at
/home/liwei/main_code/linux/arch/arm64/include/asm/kgdb.h:21
21 asm ("brk %0" : : "I" (KGDB_COMPILED_DBG_BRK_IMM));
(gdb) b printk
Breakpoint 1 at 0xffff8000101486cc: file
/home/liwei/main_code/linux/kernel/printk/printk.c, line 2076.
(gdb) c
Continuing.
[New Thread 287]
[Switching to Thread 283]
Thread 177 hit Breakpoint 1, printk (fmt=0xffff80001130c9d8 "\001\066sysrq:
HELP : ")
at /home/liwei/main_code/linux/kernel/printk/printk.c:2076
2076 {
(gdb) stepi
el1_irq () at /home/liwei/main_code/linux/arch/arm64/kernel/entry.S:608
608 irq_handler
(gdb)
After this patch:
* kdb:
Entering kdb (current=0xffff8000119d2dc0, pid 0) on processor 0 due to Keyboard
Entry
[0]kdb> bp printk
Instruction(i) BP #0 at 0xffff80001014874c (printk)
is enabled addr at ffff80001014874c, hardtype=0 installed=0
[0]kdb> g
/ # echo h > /proc/sysrq-trigger
Entering kdb (current=0xffff0000fa6948c0, pid 265) on processor 0 due to
Breakpoint @ 0xffff80001014874c
[0]kdb> ss
Entering kdb (current=0xffff0000fa6948c0, pid 265) on processor 0 due to SS
trap @ 0xffff800010148750
[0]kdb>
* kgdb:
(gdb) target remote 127.1:23002
Remote debugging using 127.1:23002
arch_kgdb_breakpoint () at
/home/liwei/main_code/linux/arch/arm64/include/asm/kgdb.h:21
21 asm ("brk %0" : : "I" (KGDB_COMPILED_DBG_BRK_IMM));
(gdb) b printk
Breakpoint 1 at 0xffff80001014874c: file
/home/liwei/main_code/linux/kernel/printk/printk.c, line 2076.
(gdb) c
Continuing.
[New Thread 277]
[Switching to Thread 276]
Thread 171 hit Breakpoint 1, printk (fmt=0xffff8000112fc130 "\001\066sysrq:
HELP : ")
at /home/liwei/main_code/linux/kernel/printk/printk.c:2076
2076 {
(gdb) stepi
0xffff800010148750 2076 {
(gdb)
Fixes: 44679a4f142b ("arm64: KGDB: Add step debugging support")
Signed-off-by: Wei Li <liwei...@huawei.com>
---
arch/arm64/kernel/kgdb.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
index 1a157ca33262..3910ac06c261 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -100,6 +100,8 @@ struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
{ "fpcr", 4, -1 },
};
+static DEFINE_PER_CPU(unsigned long, kgdb_ss_flags);
+
char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
{
if (regno >= DBG_MAX_REG_NUM || regno < 0)
@@ -200,8 +202,11 @@ int kgdb_arch_handle_exception(int exception_vector, int
signo,
/*
* Received continue command, disable single step
*/
- if (kernel_active_single_step())
+ if (kernel_active_single_step()) {
+ kernel_cleanup_single_step(per_cpu(kgdb_ss_flags,
+ raw_smp_processor_id()), linux_regs);
kernel_disable_single_step();
+ }
err = 0;
break;
@@ -221,8 +226,12 @@ int kgdb_arch_handle_exception(int exception_vector, int
signo,
/*
* Enable single step handling
*/
- if (!kernel_active_single_step())
+ if (!kernel_active_single_step()) {
+ kernel_prepare_single_step(&per_cpu(kgdb_ss_flags,
+ raw_smp_processor_id()), linux_regs);
kernel_enable_single_step(linux_regs);
+ }
+
err = 0;
break;
default:
--
2.17.1
