From: Adam Litke <agl@us.ibm.com>
(This is a big improvement, and -fomit-frame-pointer seems to make no
difference at all to generated code size. Maybe we should kill off
-fomit-frame-pointer).
Teach the x86 stack tracing code to use frame pointers, if they are available.
The show_trace() for the CONFIG_FRAME_POINTER case will now be called the same
way as the existing code. This brings up a question though. It doesn't
appear to me that anyone is actually calling show_trace_task() yet. Am I
missing something or should we change all the callers of show_trace() to use
show_trace_task()?
I hacked read_profile() a bit so I could catch it inside down(). This looks
good to me. In fact, even the inline asm functions were recognized.
cat D 00000246 0 215 212 (NOTLB)
Call Trace:
f296feec 00000086 f296ff60 00000246 f296ff10 f681dd60
00000004 f2b59ce8 f2b59d6c f296fed0 c04b4c80 c04b6680
f296fee4 c01d7f2a bffffafc f296ff08 002e58e9 08848a79
00000018 c1a0cbe0 f29a2160 f29a2328 f296ff18
[<c01079b2>] __down+0x76/0xe0
00000400 00000000 0804c038 f29a2160 00000001 f29a2160
c0118c8c f296ff6c f296ff6c f296ff2c
[<c0107b7f>] __down_failed+0xb/0x14
f296ff60 f296ff68 f296ff6c f296ff74
[<c017887e>] .text.lock.proc_misc+0xf/0x21
00000000 f2a851e0 f2a85200 000011b4 00000000 40869be4
15b4a440 40869be4 15b4a440 40869be4 00000004 ffffffff
00000001 00000001 f296ff10 f296ff10 f296ff98
[<c014a62e>] vfs_read+0x9e/0xd0
f2a851e0 0804c038 00000400 f2a85200 f2a851e0 fffffff7
0804c038 f296ffbc
[<c014a810>] sys_read+0x30/0x50
f2a851e0 0804c038 00000400 f2a85200 00000003 00000400
00000000 f296e000
[<c0108aff>] syscall_call+0x7/0xb
The top stack frame is defined to be all values from esp to ebp. Subsequent
frames are defined as ebp to *ebp (if ebp is a valid stack address).
Therefore in the worst case, a stack frame may include data from two "logical
functions" if a new frame was not defined (but we will not lose any data).
GCC seems to be generating frame-pointer enabled code even for inline asm
calls so we should only see this "worst-case" behavior around actual assembly
functions.
---
25-akpm/arch/i386/kernel/traps.c | 68 ++++++++++++++++++++++++++++++---------
1 files changed, 53 insertions(+), 15 deletions(-)
diff -puN arch/i386/kernel/traps.c~frame-pointer-based-stack-dumps arch/i386/kernel/traps.c
--- 25/arch/i386/kernel/traps.c~frame-pointer-based-stack-dumps Thu Apr 29 16:35:49 2004
+++ 25-akpm/arch/i386/kernel/traps.c Thu Apr 29 16:35:49 2004
@@ -94,27 +94,65 @@ asmlinkage void machine_check(void);
static int kstack_depth_to_print = 24;
-void show_trace(struct task_struct *task, unsigned long * stack)
+#define valid_stack_ptr(task, p) \
+ ((struct thread_info*)p > task->thread_info) && \
+ !kstack_end((unsigned long*)p)
+
+#ifdef CONFIG_FRAME_POINTER
+void print_context_stack(struct task_struct *task, unsigned long * stack,
+ unsigned long ebp)
{
unsigned long addr;
- if (!stack)
- stack = (unsigned long*)&stack;
+ while (valid_stack_ptr(task, ebp)) {
+ addr = *(unsigned long *) (ebp + 4);
+ printk(" [<%08lx>] ", addr);
+ print_symbol("%s", addr);
+ printk("\n");
+ ebp = *(unsigned long *) ebp;
+ }
+}
+#else
+void print_context_stack(struct task_struct *task, unsigned long * stack,
+ unsigned long ebp)
+{
+ unsigned long addr;
- printk("Call Trace:");
-#ifdef CONFIG_KALLSYMS
- printk("\n");
+ while (!kstack_end(stack)) {
+ addr = *stack++;
+ if (kernel_text_address(addr)) {
+ printk(" [<%08lx>] ", addr);
+ print_symbol("%s\n", addr);
+ }
+ }
+}
#endif
+
+void show_trace(struct task_struct *task, unsigned long * stack)
+{
+ unsigned long ebp;
+
+ if (!task)
+ task = current;
+
+ if (!valid_stack_ptr(task, stack)) {
+ printk("Stack pointer is garbage, not printing trace\n");
+ return;
+ }
+
+ if (task == current) {
+ /* Grab ebp right from our regs */
+ asm ("movl %%ebp, %0" : "=r" (ebp) : );
+ } else {
+ /* ebp is the last reg pushed by switch_to */
+ ebp = *(unsigned long *) task->thread.esp;
+ }
+
while (1) {
struct thread_info *context;
- context = (struct thread_info*) ((unsigned long)stack & (~(THREAD_SIZE - 1)));
- while (!kstack_end(stack)) {
- addr = *stack++;
- if (kernel_text_address(addr)) {
- printk(" [<%08lx>] ", addr);
- print_symbol("%s\n", addr);
- }
- }
+ context = (struct thread_info*)
+ ((unsigned long)stack & (~(THREAD_SIZE - 1)));
+ print_context_stack(task, stack, ebp);
stack = (unsigned long*)context->previous_esp;
if (!stack)
break;
@@ -143,7 +181,7 @@ void show_stack(struct task_struct *task
printk("\n ");
printk("%08lx ", *stack++);
}
- printk("\n");
+ printk("\nCall Trace:\n");
show_trace(task, esp);
}
_