1 files changed, 34 insertions, 2 deletions

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 9a52349874ee..e15c521846ca 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];