riscv: stacktrace: fix the riscv stacktrace when CONFIG_FRAME_POINTER enabled

As [1] and [2] said, the arch_stack_walk should not to trace itself, or it will
leave the trace unexpectedly when called. The example is when we do "cat
/sys/kernel/debug/page_owner", all pages' stack is the same.

arch_stack_walk+0x18/0x20
stack_trace_save+0x40/0x60
register_dummy_stack+0x24/0x5e
init_page_owner+0x2e

So we use __builtin_frame_address(1) as the first frame to be walked. And mark
the arch_stack_walk() noinline.

We found that pr_cont will affact pages' stack whose task state is RUNNING when
testing "echo t > /proc/sysrq-trigger". So move the place of pr_cont and mark
the function dump_backtrace() noinline.

Also we move the case when task == NULL into else branch, and test for it in
"echo c > /proc/sysrq-trigger".

[1] https://lore.kernel.org/lkml/20210319184106.5688-1-mark.rutland@arm.com/
[2] https://lore.kernel.org/lkml/20210317142050.57712-1-chenjun102@huawei.com/

Signed-off-by: Chen Huang <chenhuang5@huawei.com>
Fixes: 5d8544e2d007 ("RISC-V: Generic library routines and assembly")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 2b3e0cb..bde85fc 100644 (file)
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -27,10 +27,10 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
                fp = frame_pointer(regs);
                sp = user_stack_pointer(regs);
                pc = instruction_pointer(regs);
-       } else if (task == NULL || task == current) {
-               fp = (unsigned long)__builtin_frame_address(0);
-               sp = sp_in_global;
-               pc = (unsigned long)walk_stackframe;
+       } else if (task == current) {
+               fp = (unsigned long)__builtin_frame_address(1);
+               sp = (unsigned long)__builtin_frame_address(0);
+               pc = (unsigned long)__builtin_return_address(0);
        } else {
                /* task blocked in __switch_to */
                fp = task->thread.s[0];
@@ -106,15 +106,15 @@ static bool print_trace_address(void *arg, unsigned long pc)
        return true;
 }
 
-void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
+noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
                    const char *loglvl)
 {
-       pr_cont("%sCall Trace:\n", loglvl);
        walk_stackframe(task, regs, print_trace_address, (void *)loglvl);
 }
 
 void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
 {
+       pr_cont("%sCall Trace:\n", loglvl);
        dump_backtrace(NULL, task, loglvl);
 }
 
@@ -139,7 +139,7 @@ unsigned long get_wchan(struct task_struct *task)
 
 #ifdef CONFIG_STACKTRACE
 
-void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
                     struct task_struct *task, struct pt_regs *regs)
 {
        walk_stackframe(task, regs, consume_entry, cookie);