ARM: 9234/1: stacktrace: Avoid duplicate saving of exception PC value

Because an exception stack frame is not created in the exception entry,
save_trace() does special handling for the exception PC, but this is
only needed when CONFIG_FRAME_POINTER_UNWIND=y. When
CONFIG_ARM_UNWIND=y, unwind annotations have been added to the exception
entry and save_trace() will repeatedly save the exception PC:

    [0x7f000090] hrtimer_hander+0x8/0x10 [hrtimer]
    [0x8019ec50] __hrtimer_run_queues+0x18c/0x394
    [0x8019f760] hrtimer_run_queues+0xbc/0xd0
    [0x8019def0] update_process_times+0x34/0x80
    [0x801ad2a4] tick_periodic+0x48/0xd0
    [0x801ad3dc] tick_handle_periodic+0x1c/0x7c
    [0x8010f2e0] twd_handler+0x30/0x40
    [0x80177620] handle_percpu_devid_irq+0xa0/0x23c
    [0x801718d0] generic_handle_domain_irq+0x24/0x34
    [0x80502d28] gic_handle_irq+0x74/0x88
    [0x8085817c] generic_handle_arch_irq+0x58/0x78
    [0x80100ba8] __irq_svc+0x88/0xc8
    [0x80108114] arch_cpu_idle+0x38/0x3c
    [0x80108114] arch_cpu_idle+0x38/0x3c    <==== duplicate saved exception PC
    [0x80861bf8] default_idle_call+0x38/0x130
    [0x8015d5cc] do_idle+0x150/0x214
    [0x8015d978] cpu_startup_entry+0x18/0x1c
    [0x808589c0] rest_init+0xd8/0xdc
    [0x80c00a44] arch_post_acpi_subsys_init+0x0/0x8

We can move the special handling of the exception PC in save_trace() to
the unwind_frame() of the frame pointer unwinder.

Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Reviewed-by: Linus Waleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
index dd19a46..36b2ff4 100644 (file)
--- a/arch/arm/include/asm/stacktrace.h
+++ b/arch/arm/include/asm/stacktrace.h
@@ -21,6 +21,9 @@ struct stackframe {
        struct llist_node *kr_cur;
        struct task_struct *tsk;
 #endif
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+       bool ex_frame;
+#endif
 };
 
 static __always_inline
@@ -34,6 +37,9 @@ void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
                frame->kr_cur = NULL;
                frame->tsk = current;
 #endif
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+               frame->ex_frame = in_entry_text(frame->pc);
+#endif
 }
 
 extern int unwind_frame(struct stackframe *frame);

diff --git a/arch/arm/kernel/return_address.c b/arch/arm/kernel/return_address.c
index 8aac1e1..38f1ea9 100644 (file)
--- a/arch/arm/kernel/return_address.c
+++ b/arch/arm/kernel/return_address.c
@@ -47,6 +47,7 @@ here:
        frame.kr_cur = NULL;
        frame.tsk = current;
 #endif
+       frame.ex_frame = false;
 
        walk_stackframe(&frame, save_return_addr, &data);
 

diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index af87040..85443b5 100644 (file)
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -82,6 +82,27 @@ int notrace unwind_frame(struct stackframe *frame)
        if (frame_pointer_check(frame))
                return -EINVAL;
 
+       /*
+        * When we unwind through an exception stack, include the saved PC
+        * value into the stack trace.
+        */
+       if (frame->ex_frame) {
+               struct pt_regs *regs = (struct pt_regs *)frame->sp;
+
+               /*
+                * We check that 'regs + sizeof(struct pt_regs)' (that is,
+                * &regs[1]) does not exceed the bottom of the stack to avoid
+                * accessing data outside the task's stack. This may happen
+                * when frame->ex_frame is a false positive.
+                */
+               if ((unsigned long)&regs[1] > ALIGN(frame->sp, THREAD_SIZE))
+                       return -EINVAL;
+
+               frame->pc = regs->ARM_pc;
+               frame->ex_frame = false;
+               return 0;
+       }
+
        /* restore the registers from the stack frame */
 #ifdef CONFIG_CC_IS_CLANG
        frame->sp = frame->fp;
@@ -98,6 +119,9 @@ int notrace unwind_frame(struct stackframe *frame)
                                        (void *)frame->fp, &frame->kr_cur);
 #endif
 
+       if (in_entry_text(frame->pc))
+               frame->ex_frame = true;
+
        return 0;
 }
 #endif
@@ -128,7 +152,6 @@ static int save_trace(struct stackframe *frame, void *d)
 {
        struct stack_trace_data *data = d;
        struct stack_trace *trace = data->trace;
-       struct pt_regs *regs;
        unsigned long addr = frame->pc;
 
        if (data->no_sched_functions && in_sched_functions(addr))
@@ -139,19 +162,6 @@ static int save_trace(struct stackframe *frame, void *d)
        }
 
        trace->entries[trace->nr_entries++] = addr;
-
-       if (trace->nr_entries >= trace->max_entries)
-               return 1;
-
-       if (!in_entry_text(frame->pc))
-               return 0;
-
-       regs = (struct pt_regs *)frame->sp;
-       if ((unsigned long)&regs[1] > ALIGN(frame->sp, THREAD_SIZE))
-               return 0;
-
-       trace->entries[trace->nr_entries++] = regs->ARM_pc;
-
        return trace->nr_entries >= trace->max_entries;
 }
 
@@ -193,6 +203,9 @@ here:
        frame.kr_cur = NULL;
        frame.tsk = tsk;
 #endif
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+       frame.ex_frame = false;
+#endif
 
        walk_stackframe(&frame, save_trace, &data);
 }
@@ -214,6 +227,9 @@ void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
        frame.kr_cur = NULL;
        frame.tsk = current;
 #endif
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+       frame.ex_frame = in_entry_text(frame.pc);
+#endif
 
        walk_stackframe(&frame, save_trace, &data);
 }