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Subject[PATCH] [23/45] i386: Make callgraph use dump_trace() on i386/x86_64
Date

From: jblunck@suse.de
This patch improves oprofile callgraphs for i386/x86_64. The old backtracing
code was unable to produce even kernel backtraces if the kernel wasn't
compiled with framepointers. The code now uses dump_trace().

Signed-off-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/i386/oprofile/backtrace.c | 104 ++++++++++++++---------------------------
1 file changed, 38 insertions(+), 66 deletions(-)

Index: linux/arch/i386/oprofile/backtrace.c
===================================================================
--- linux.orig/arch/i386/oprofile/backtrace.c
+++ linux/arch/i386/oprofile/backtrace.c
@@ -13,25 +13,45 @@
#include <linux/mm.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
+#include <asm/stacktrace.h>

-struct frame_head {
- struct frame_head * ebp;
- unsigned long ret;
-} __attribute__((packed));
+static void backtrace_warning_symbol(void *data, char *msg,
+ unsigned long symbol)
+{
+ /* Ignore warnings */
+}

-static struct frame_head *
-dump_kernel_backtrace(struct frame_head * head)
+static void backtrace_warning(void *data, char *msg)
{
- oprofile_add_trace(head->ret);
+ /* Ignore warnings */
+}

- /* frame pointers should strictly progress back up the stack
- * (towards higher addresses) */
- if (head >= head->ebp)
- return NULL;
+static int backtrace_stack(void *data, char *name)
+{
+ /* Yes, we want all stacks */
+ return 0;
+}

- return head->ebp;
+static void backtrace_address(void *data, unsigned long addr)
+{
+ unsigned int *depth = data;
+
+ if ((*depth)--)
+ oprofile_add_trace(addr);
}

+static struct stacktrace_ops backtrace_ops = {
+ .warning = backtrace_warning,
+ .warning_symbol = backtrace_warning_symbol,
+ .stack = backtrace_stack,
+ .address = backtrace_address,
+};
+
+struct frame_head {
+ struct frame_head * ebp;
+ unsigned long ret;
+} __attribute__((packed));
+
static struct frame_head *
dump_user_backtrace(struct frame_head * head)
{
@@ -53,72 +73,24 @@ dump_user_backtrace(struct frame_head *
return bufhead[0].ebp;
}

-/*
- * | | /\ Higher addresses
- * | |
- * --------------- stack base (address of current_thread_info)
- * | thread info |
- * . .
- * | stack |
- * --------------- saved regs->ebp value if valid (frame_head address)
- * . .
- * --------------- saved regs->rsp value if x86_64
- * | |
- * --------------- struct pt_regs * stored on stack if 32-bit
- * | |
- * . .
- * | |
- * --------------- %esp
- * | |
- * | | \/ Lower addresses
- *
- * Thus, regs (or regs->rsp for x86_64) <-> stack base restricts the
- * valid(ish) ebp values. Note: (1) for x86_64, NMI and several other
- * exceptions use special stacks, maintained by the interrupt stack table
- * (IST). These stacks are set up in trap_init() in
- * arch/x86_64/kernel/traps.c. Thus, for x86_64, regs now does not point
- * to the kernel stack; instead, it points to some location on the NMI
- * stack. On the other hand, regs->rsp is the stack pointer saved when the
- * NMI occurred. (2) For 32-bit, regs->esp is not valid because the
- * processor does not save %esp on the kernel stack when interrupts occur
- * in the kernel mode.
- */
-#ifdef CONFIG_FRAME_POINTER
-static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
-{
- unsigned long headaddr = (unsigned long)head;
-#ifdef CONFIG_X86_64
- unsigned long stack = (unsigned long)regs->rsp;
-#else
- unsigned long stack = (unsigned long)regs;
-#endif
- unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
-
- return headaddr > stack && headaddr < stack_base;
-}
-#else
-/* without fp, it's just junk */
-static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
-{
- return 0;
-}
-#endif
-
-
void
x86_backtrace(struct pt_regs * const regs, unsigned int depth)
{
struct frame_head *head;
+ unsigned long stack;

#ifdef CONFIG_X86_64
head = (struct frame_head *)regs->rbp;
+ stack = regs->rsp;
#else
head = (struct frame_head *)regs->ebp;
+ stack = regs->esp;
#endif

if (!user_mode_vm(regs)) {
- while (depth-- && valid_kernel_stack(head, regs))
- head = dump_kernel_backtrace(head);
+ if (depth)
+ dump_trace(NULL, regs, (unsigned long *)stack,
+ &backtrace_ops, &depth);
return;
}

-
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