When unwinding on __kretprobe_trampoline, the caller of traced function
will be skipped because unwinder doesn't read the saved pt_regs.
Things going like this:
caller's caller | ... |<---+
caller +---------------------------+ |
| ra caller's caller | |
| s0 of caller's caller | |
| ... | |
probed func returned +---------------------------+ |
__kretprobe_trampoline | pt_regs: | |
| epc caller | |
| ra __kretprobe_trampoline| |
| ... | |
| s0 of caller | {ra, fp}
| ... |
Since from caller to __kretprobe_trampoline, the {ra, fp} are not
changed, unwinder will go directly to caller's caller.
Now we can have an ENCODED_FRAME_POINTER on stack and read the pt_regs,
kretporbe will set the epc to correct_ret_addr so that we can unwind
to the correct caller.
Stacktrace before this patch:
Call Trace:
...
[<ffffffff800d5d48>] __kretprobe_trampoline_handler+0xc2/0x13e
[<ffffffff808b766c>] trampoline_probe_handler+0x30/0x46
[<ffffffff800070de>] __kretprobe_trampoline+0x52/0x92
[<ffffffff0163809c>] kprobe_init+0x9c/0x1000 [kprobe_unwind]
[<ffffffff800027c8>] do_one_initcall+0x4c/0x1f2
...
Stacktrace after this patch:
Call Trace:
...
[<ffffffff800d5d48>] __kretprobe_trampoline_handler+0xc2/0x13e
[<ffffffff808b766c>] trampoline_probe_handler+0x30/0x46
[<ffffffff800070de>] __kretprobe_trampoline+0x52/0x92
+ [<ffffffff01633076>] the_caller+0x2c/0x38 [kprobe_unwind]
[<ffffffff0163809c>] kprobe_init+0x9c/0x1000 [kprobe_unwind]
[<ffffffff800027c8>] do_one_initcall+0x4c/0x1f2
...
Signed-off-by: Chen Zhongjin <[email protected]>
---
arch/riscv/include/asm/stacktrace.h | 4 ++++
arch/riscv/kernel/probes/kprobes_trampoline.S | 8 ++++++++
arch/riscv/kernel/stacktrace.c | 5 +++++
3 files changed, 17 insertions(+)
diff --git a/arch/riscv/include/asm/stacktrace.h b/arch/riscv/include/asm/stacktrace.h
index a39e4ef1dbd5..506c7c38b6cb 100644
--- a/arch/riscv/include/asm/stacktrace.h
+++ b/arch/riscv/include/asm/stacktrace.h
@@ -16,6 +16,10 @@ struct unwind_state {
unsigned long sp;
unsigned long pc;
struct pt_regs *regs;
+#ifdef CONFIG_KRETPROBES
+ struct llist_node *kr_cur;
+ struct task_struct *task;
+#endif
};
extern void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
diff --git a/arch/riscv/kernel/probes/kprobes_trampoline.S b/arch/riscv/kernel/probes/kprobes_trampoline.S
index 7bdb09ded39b..3c0677a714a6 100644
--- a/arch/riscv/kernel/probes/kprobes_trampoline.S
+++ b/arch/riscv/kernel/probes/kprobes_trampoline.S
@@ -6,6 +6,8 @@
#include <asm/asm.h>
#include <asm/asm-offsets.h>
+#include <asm/frame.h>
+#include <asm/csr.h>
.text
.altmacro
@@ -79,6 +81,12 @@ ENTRY(__kretprobe_trampoline)
addi sp, sp, -(PT_SIZE_ON_STACK)
save_all_base_regs
+#ifdef CONFIG_FRAME_POINTER
+ li s0, SR_PP
+ REG_S s0, PT_STATUS(sp)
+ ENCODE_FRAME_POINTER
+#endif
+
move a0, sp /* pt_regs */
call trampoline_probe_handler
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 976dc298ab3b..53edc685ca18 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -11,6 +11,7 @@
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>
#include <linux/ftrace.h>
+#include <linux/kprobes.h>
#include <asm/stacktrace.h>
@@ -123,6 +124,10 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
state.sp = task->thread.sp;
state.pc = task->thread.ra;
}
+#ifdef CONFIG_KRETPROBES
+ state.kr_cur = NULL;
+ state.task = task;
+#endif
unwind(&state, consume_entry, cookie);
}
--
2.17.1