openkylin
/
linux
mirror of https://gitee.com/openkylin/linux.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

powerpc/kprobe: Don't emulate store when kprobe stwu r1 

We don't do the real store operation for kprobing 'stwu Rx,(y)R1'
since this may corrupt the exception frame, now we will do this
operation safely in exception return code after migrate current
exception frame below the kprobed function stack.

So we only update gpr[1] here and trigger a thread flag to mask
this.

Note we should make sure if we trigger kernel stack over flow.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Tiejun Chen 2012-09-16 23:54:31 +00:00 committed by Benjamin Herrenschmidt
parent a9c4e541ea
commit 8e9f693715
1 changed files with 34 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
arch/powerpc/lib/sstep.c
View File

@ -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];