x86: pull bp calculation earlier into the backtrace path

Right now, we take the stack pointer early during the backtrace path, but
only calculate bp several functions deep later, making it hard to reconcile
the stack and bp backtraces (as well as showing several internal backtrace
functions on the stack with bp based backtracing).

This patch moves the bp taking to the same place we take the stack pointer;
sadly this ripples through several layers of the back tracing stack,
but it's not all that bad in the end I hope.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 17 insertions, 22 deletions

diff --git a/arch/x86/kernel/traps_32.c b/arch/x86/kernel/traps_32.c
index 959d40edecd5..6f3bb287c702 100644
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -120,15 +120,6 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo,
 {
         struct stack_frame *frame = (struct stack_frame *)bp;
 
-        /*
-         * if EBP is "deeper" into the stack than the actual stack pointer,
-         * we need to rewind the stack pointer a little to start at the
-         * first stack frame, but only if EBP is in this stack frame.
-         */
-        if (stack > (unsigned long *) bp
-                        && valid_stack_ptr(tinfo, frame, sizeof(*frame)))
-                stack = (unsigned long *) bp;
-
         while (valid_stack_ptr(tinfo, stack, sizeof(*stack))) {
                 unsigned long addr;
 
@@ -139,7 +130,7 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo,
                                 frame = frame->next_frame;
                                 bp = (unsigned long) frame;
                         } else {
-                                ops->address(data, addr, 0);
+                                ops->address(data, addr, bp == 0);
                         }
                 }
                 stack++;
@@ -150,11 +141,9 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo,
 #define MSG(msg) ops->warning(data, msg)
 
 void dump_trace(struct task_struct *task, struct pt_regs *regs,
-                unsigned long *stack,
+                unsigned long *stack, unsigned long bp,
                 const struct stacktrace_ops *ops, void *data)
 {
-        unsigned long bp = 0;
-
         if (!task)
                 task = current;
 
@@ -234,20 +223,20 @@ static const struct stacktrace_ops print_trace_ops = {
 
 static void
 show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
-                   unsigned long * stack, char *log_lvl)
+                unsigned long *stack, unsigned long bp, char *log_lvl)
 {
-        dump_trace(task, regs, stack, &print_trace_ops, log_lvl);
+        dump_trace(task, regs, stack, bp, &print_trace_ops, log_lvl);
         printk("%s =======================\n", log_lvl);
 }
 
 void show_trace(struct task_struct *task, struct pt_regs *regs,
-                unsigned long * stack)
+                unsigned long *stack, unsigned long bp)
 {
-        show_trace_log_lvl(task, regs, stack, "");
+        show_trace_log_lvl(task, regs, stack, bp, "");
 }
 
 static void show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
-                               unsigned long *sp, char *log_lvl)
+                       unsigned long *sp, unsigned long bp, char *log_lvl)
 {
         unsigned long *stack;
         int i;
@@ -268,13 +257,13 @@ static void show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
                 printk("%08lx ", *stack++);
         }
         printk("\n%sCall Trace:\n", log_lvl);
-        show_trace_log_lvl(task, regs, sp, log_lvl);
+        show_trace_log_lvl(task, regs, sp, bp, log_lvl);
 }
 
 void show_stack(struct task_struct *task, unsigned long *sp)
 {
         printk("       ");
-        show_stack_log_lvl(task, NULL, sp, "");
+        show_stack_log_lvl(task, NULL, sp, 0, "");
 }
 
 /*
@@ -283,13 +272,19 @@ void show_stack(struct task_struct *task, unsigned long *sp)
 void dump_stack(void)
 {
         unsigned long stack;
+        unsigned long bp = 0;
+
+#ifdef CONFIG_FRAME_POINTER
+        if (!bp)
+                asm("movl %%ebp, %0" : "=r" (bp):);
+#endif
 
         printk("Pid: %d, comm: %.20s %s %s %.*s\n",
                 current->pid, current->comm, print_tainted(),
                 init_utsname()->release,
                 (int)strcspn(init_utsname()->version, " "),
                 init_utsname()->version);
-        show_trace(current, NULL, &stack);
+        show_trace(current, NULL, &stack, bp);
 }
 
 EXPORT_SYMBOL(dump_stack);
@@ -314,7 +309,7 @@ void show_registers(struct pt_regs *regs)
                 unsigned char c;
 
                 printk("\n" KERN_EMERG "Stack: ");
-                show_stack_log_lvl(NULL, regs, &regs->sp, KERN_EMERG);
+                show_stack_log_lvl(NULL, regs, &regs->sp, 0, KERN_EMERG);
 
                 printk(KERN_EMERG "Code: ");