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Commit 257ef9d2 authored by Torok Edwin's avatar Torok Edwin Committed by Ingo Molnar
Browse files

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: default avatarTörök Edwin <edwintorok@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarFrederic 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: default avatarIngo Molnar <mingo@elte.hu>
parent b38b24ea

arch/x86/kernel/cpu/perf_event.c

+39 −5
Original line number Diff line number Diff line
@@ -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)

{

	/* 32-bit process in 64-bit kernel. */

	struct stack_frame_ia32 frame;

	const void __user *fp;



	if (!test_thread_flag(TIF_IA32))

		return 0;



	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));

		bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));

		if (bytes != sizeof(frame))

			break;



	return bytes == sizeof(*frame);

		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)

arch/x86/kernel/dumpstack.h

+5 −0
Original line number Diff line number Diff line
@@ -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;