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perf, x86: Fix callgraphs of 32-bit processes on 64-bit kernels 

When profiling a 32-bit process on a 64-bit kernel, callgraph tracing
stopped after the first function, because it has seen a garbage memory
address (tried to interpret the frame pointer, and return address as a
64-bit pointer).

Fix this by using a struct stack_frame with 32-bit pointers when the
TIF_IA32 flag is set.

Note that TIF_IA32 flag must be used, and not is_compat_task(), because
the latter is only set when the 32-bit process is executing a syscall,
which may not always be the case (when tracing page fault events for
example).

Signed-off-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
LKML-Reference: <1268820436-13145-1-git-send-email-edwintorok@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Torok Edwin 2010-03-17 12:07:16 +02:00 committed by Ingo Molnar
parent b38b24ead3
commit 257ef9d21f
2 changed files with 44 additions and 5 deletions
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44
arch/x86/kernel/cpu/perf_event.c
View File

@ -28,6 +28,7 @@
#include <asm/apic.h>
#include <asm/stacktrace.h>
#include <asm/nmi.h>
#include <asm/compat.h>
static u64 perf_event_mask __read_mostly;
@ -1630,14 +1631,42 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
return len;
}
static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
#ifdef CONFIG_COMPAT
static inline int
perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
unsigned long bytes;
/* 32-bit process in 64-bit kernel. */
struct stack_frame_ia32 frame;
const void __user *fp;
bytes = copy_from_user_nmi(frame, fp, sizeof(*frame));
if (!test_thread_flag(TIF_IA32))
return 0;
return bytes == sizeof(*frame);
fp = compat_ptr(regs->bp);
while (entry->nr < PERF_MAX_STACK_DEPTH) {
unsigned long bytes;
frame.next_frame = 0;
frame.return_address = 0;
bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
if (bytes != sizeof(frame))
break;
if (fp < compat_ptr(regs->sp))
break;
callchain_store(entry, frame.return_address);
fp = compat_ptr(frame.next_frame);
}
return 1;
}
#else
static inline int
perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
{
return 0;
}
#endif
static void
perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry)
@ -1653,11 +1682,16 @@ perf_callchain_user(struct pt_regs *regs, struct perf_callchain_entry *entry)
callchain_store(entry, PERF_CONTEXT_USER);
callchain_store(entry, regs->ip);
if (perf_callchain_user32(regs, entry))
return;
while (entry->nr < PERF_MAX_STACK_DEPTH) {
unsigned long bytes;
frame.next_frame = NULL;
frame.return_address = 0;
if (!copy_stack_frame(fp, &frame))
bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
if (bytes != sizeof(frame))
break;
if ((unsigned long)fp < regs->sp)

5
arch/x86/kernel/dumpstack.h
View File

@ -30,6 +30,11 @@ struct stack_frame {
unsigned long return_address;
};
struct stack_frame_ia32 {
u32 next_frame;
u32 return_address;
};
static inline unsigned long rewind_frame_pointer(int n)
{
struct stack_frame *frame;