perf events, x86/stacktrace: Make stack walking optional

The current print_context_stack helper that does the stack
walking job is good for usual stacktraces as it walks through
all the stack and reports even addresses that look unreliable,
which is nice when we don't have frame pointers for example.

But we have users like perf that only require reliable
stacktraces, and those may want a more adapted stack walker, so
lets make this function a callback in stacktrace_ops that users
can tune for their needs.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1261024834-5336-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

6 files changed, 19 insertions, 21 deletions

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 45506d5dd8df..d3802ee5a416 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2336,6 +2336,7 @@ static const struct stacktrace_ops backtrace_ops = {
         .warning_symbol         = backtrace_warning_symbol,
         .stack                  = backtrace_stack,
         .address                = backtrace_address,
+        .walk_stack             = print_context_stack,
 };
 
 #include "../dumpstack.h"
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 0a0aa1cec8f1..8aaa119b7cad 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -141,10 +141,11 @@ static void print_trace_address(void *data, unsigned long addr, int reliable)
 }
 
 static const struct stacktrace_ops print_trace_ops = {
-        .warning = print_trace_warning,
-        .warning_symbol = print_trace_warning_symbol,
-        .stack = print_trace_stack,
-        .address = print_trace_address,
+        .warning                = print_trace_warning,
+        .warning_symbol         = print_trace_warning_symbol,
+        .stack                  = print_trace_stack,
+        .address                = print_trace_address,
+        .walk_stack             = print_context_stack,
 };
 
 void
diff --git a/arch/x86/kernel/dumpstack.h b/arch/x86/kernel/dumpstack.h
index 81086c227ab7..4fd1420faffa 100644
--- a/arch/x86/kernel/dumpstack.h
+++ b/arch/x86/kernel/dumpstack.h
@@ -14,12 +14,6 @@
 #define get_bp(bp) asm("movq %%rbp, %0" : "=r" (bp) :)
 #endif
 
-extern unsigned long
-print_context_stack(struct thread_info *tinfo,
-                unsigned long *stack, unsigned long bp,
-                const struct stacktrace_ops *ops, void *data,
-                unsigned long *end, int *graph);
-
 extern void
 show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
                 unsigned long *stack, unsigned long bp, char *log_lvl);
diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index e0ed4c7abb62..ae775ca47b25 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -58,7 +58,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
 
                 context = (struct thread_info *)
                         ((unsigned long)stack & (~(THREAD_SIZE - 1)));
-                bp = print_context_stack(context, stack, bp, ops, data, NULL, &graph);
+                bp = ops->walk_stack(context, stack, bp, ops, data, NULL, &graph);
 
                 stack = (unsigned long *)context->previous_esp;
                 if (!stack)
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index b13af53883aa..0ad9597073f5 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -188,8 +188,8 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                         if (ops->stack(data, id) < 0)
                                 break;
 
-                        bp = print_context_stack(tinfo, stack, bp, ops,
-                                                 data, estack_end, &graph);
+                        bp = ops->walk_stack(tinfo, stack, bp, ops,
+                                             data, estack_end, &graph);
                         ops->stack(data, "<EOE>");
                         /*
                          * We link to the next stack via the
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index c3eb207181fe..922eefbb3f6c 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -53,17 +53,19 @@ save_stack_address_nosched(void *data, unsigned long addr, int reliable)
 }
 
 static const struct stacktrace_ops save_stack_ops = {
-        .warning = save_stack_warning,
-        .warning_symbol = save_stack_warning_symbol,
-        .stack = save_stack_stack,
-        .address = save_stack_address,
+        .warning        = save_stack_warning,
+        .warning_symbol = save_stack_warning_symbol,
+        .stack          = save_stack_stack,
+        .address        = save_stack_address,
+        .walk_stack     = print_context_stack,
 };
 
 static const struct stacktrace_ops save_stack_ops_nosched = {
-        .warning = save_stack_warning,
-        .warning_symbol = save_stack_warning_symbol,
-        .stack = save_stack_stack,
-        .address = save_stack_address_nosched,
+        .warning        = save_stack_warning,
+        .warning_symbol = save_stack_warning_symbol,
+        .stack          = save_stack_stack,
+        .address        = save_stack_address_nosched,
+        .walk_stack     = print_context_stack,
 };
 
 /*