x86: fix kernel panic on 32 bits when profiling

Latest kernel has a kernel panic in booting on i386 machine when
profile=2 setting in cmdline.  It is due to 'sp' being incorrect in
profile_pc().

BUG: unable to handle kernel NULL pointer dereference at 00000246
IP: [<c01288b6>] profile_pc+0x2a/0x48
*pde = 00000000
Oops: 0000 [#1] SMP

This differs from the original version by Alex Shi in that we use the
kernel_stack_pointer() inline already defined in <asm/ptrace.h> for
this purpose, instead of #ifdef.

Originally-by: Alex Shi <alex.shi@intel.com>
Cc: "Chen, Tim C" <tim.c.chen@intel.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index dcb00d2..be25734 100644 (file)
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -38,7 +38,8 @@ unsigned long profile_pc(struct pt_regs *regs)
 #ifdef CONFIG_FRAME_POINTER
                return *(unsigned long *)(regs->bp + sizeof(long));
 #else
-               unsigned long *sp = (unsigned long *)regs->sp;
+               unsigned long *sp =
+                       (unsigned long *)kernel_stack_pointer(regs);
                /*
                 * Return address is either directly at stack pointer
                 * or above a saved flags. Eflags has bits 22-31 zero,