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Commit 0d69a052 authored by Gui,Jian's avatar Gui,Jian Committed by Paul Mackerras
Browse files

[POWERPC] Disallow kprobes on emulate_step and branch_taken 



On powerpc, probing on emulate_step function will crash 2.6.18.1 when
it is triggered.

When kprobe is triggered, emulate_step() is on its kernel path and
will cause recursive kprobe fault.  And branch_taken() is called
in emulate_step().  This disallows kprobes on both of them.

Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 292f86f0

arch/powerpc/lib/sstep.c

+3 −2
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
 * 2 of the License, or (at your option) any later version.

 */

#include <linux/kernel.h>

#include <linux/kprobes.h>

#include <linux/ptrace.h>

#include <asm/sstep.h>

#include <asm/processor.h>
@@ -25,7 +26,7 @@ extern char system_call_common[]; 
/*

 * Determine whether a conditional branch instruction would branch.

 */

static int branch_taken(unsigned int instr, struct pt_regs *regs)

static int __kprobes branch_taken(unsigned int instr, struct pt_regs *regs)

{

	unsigned int bo = (instr >> 21) & 0x1f;

	unsigned int bi;
@@ -51,7 +52,7 @@ static int branch_taken(unsigned int instr, struct pt_regs *regs) 
 * or -1 if the instruction is one that should not be stepped,

 * such as an rfid, or a mtmsrd that would clear MSR_RI.

 */

int emulate_step(struct pt_regs *regs, unsigned int instr)

int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)

{

	unsigned int opcode, rd;

	unsigned long int imm;