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Diffstat (limited to 'arch/powerpc/lib/sstep.c')
-rw-r--r--arch/powerpc/lib/sstep.c36
1 files changed, 34 insertions, 2 deletions
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 9a52349874e..e15c521846c 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -566,7 +566,7 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
unsigned long int ea;
unsigned int cr, mb, me, sh;
int err;
- unsigned long old_ra;
+ unsigned long old_ra, val3;
long ival;
opcode = instr >> 26;
@@ -1486,11 +1486,43 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
goto ldst_done;
case 36: /* stw */
- case 37: /* stwu */
val = regs->gpr[rd];
err = write_mem(val, dform_ea(instr, regs), 4, regs);
goto ldst_done;
+ case 37: /* stwu */
+ val = regs->gpr[rd];
+ val3 = dform_ea(instr, regs);
+ /*
+ * For PPC32 we always use stwu to change stack point with r1. So
+ * this emulated store may corrupt the exception frame, now we
+ * have to provide the exception frame trampoline, which is pushed
+ * below the kprobed function stack. So we only update gpr[1] but
+ * don't emulate the real store operation. We will do real store
+ * operation safely in exception return code by checking this flag.
+ */
+ if ((ra == 1) && !(regs->msr & MSR_PR) \
+ && (val3 >= (regs->gpr[1] - STACK_INT_FRAME_SIZE))) {
+ /*
+ * Check if we will touch kernel sack overflow
+ */
+ if (val3 - STACK_INT_FRAME_SIZE <= current->thread.ksp_limit) {
+ printk(KERN_CRIT "Can't kprobe this since Kernel stack overflow.\n");
+ err = -EINVAL;
+ break;
+ }
+
+ /*
+ * Check if we already set since that means we'll
+ * lose the previous value.
+ */
+ WARN_ON(test_thread_flag(TIF_EMULATE_STACK_STORE));
+ set_thread_flag(TIF_EMULATE_STACK_STORE);
+ err = 0;
+ } else
+ err = write_mem(val, val3, 4, regs);
+ goto ldst_done;
+
case 38: /* stb */
case 39: /* stbu */
val = regs->gpr[rd];