From 0754dedadf2c026bc8075fb9600d4bd313fdc4a0 Mon Sep 17 00:00:00 2001
From: Tiejun Chen <tiejun.chen@windriver.com>
Date: Sun, 16 Sep 2012 23:54:31 +0000
Subject: [PATCH] --- yaml --- r: 330334 b: refs/heads/master c:
 8e9f69371536981a2a8c9ee4a49dbe3aa4946df4 h: refs/heads/master v: v3

---
 [refs]                         |  2 +-
 trunk/arch/powerpc/lib/sstep.c | 36 ++++++++++++++++++++++++++++++++--
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index d59bf7952e68..2db99a21a7b8 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a9c4e541ea9b22944da356f2a9258b4eddcc953b
+refs/heads/master: 8e9f69371536981a2a8c9ee4a49dbe3aa4946df4
diff --git a/trunk/arch/powerpc/lib/sstep.c b/trunk/arch/powerpc/lib/sstep.c
index 9a52349874ee..e15c521846ca 100644
--- a/trunk/arch/powerpc/lib/sstep.c
+++ b/trunk/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];