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[ARM] 5558/1: Add extra checks to ARM unwinder to avoid tracing corrupt stacks

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There are situations where the unwinder goes beyond stack boundaries and
unwinds random data. This patch moves the stack boundaries check after
the unwind_exec_insn() call and adds an extra check for possible
infinite loops (like "mov pc, lr" with pc == lr).

The patch also fixes a bug in the unwind instructions interpreter. The
0xb0 instruction can only set PC to LR if this wasn't already set by
a previous instruction (this is used on exceptions taken while in kernel
mode where svc_entry is annotated with ".save {r0 - pc}").

Tested-by: Tony Lindgren <tony@atomide.com>

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Catalin Marinas 2009-06-19 16:42:11 +01:00 committed by Russell King
parent 7436127ce9
commit c894ed6956
1 changed files with 9 additions and 10 deletions
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19
arch/arm/kernel/unwind.c
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@ -212,7 +212,8 @@ static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
ctrl->vrs[14] = *vsp++;
ctrl->vrs[SP] = (unsigned long)vsp;
} else if (insn == 0xb0) {
ctrl->vrs[PC] = ctrl->vrs[LR];
if (ctrl->vrs[PC] == 0)
ctrl->vrs[PC] = ctrl->vrs[LR];
/* no further processing */
ctrl->entries = 0;
} else if (insn == 0xb1) {
@ -309,18 +310,20 @@ int unwind_frame(struct stackframe *frame)
}
while (ctrl.entries > 0) {
int urc;
if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
return -URC_FAILURE;
urc = unwind_exec_insn(&ctrl);
int urc = unwind_exec_insn(&ctrl);
if (urc < 0)
return urc;
if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
return -URC_FAILURE;
}
if (ctrl.vrs[PC] == 0)
ctrl.vrs[PC] = ctrl.vrs[LR];
/* check for infinite loop */
if (frame->pc == ctrl.vrs[PC])
return -URC_FAILURE;
frame->fp = ctrl.vrs[FP];
frame->sp = ctrl.vrs[SP];
frame->lr = ctrl.vrs[LR];
@ -332,7 +335,6 @@ int unwind_frame(struct stackframe *frame)
void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
struct stackframe frame;
unsigned long high, low;
register unsigned long current_sp asm ("sp");
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
@ -362,9 +364,6 @@ void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
frame.pc = thread_saved_pc(tsk);
}
low = frame.sp & ~(THREAD_SIZE - 1);
high = low + THREAD_SIZE;
while (1) {
int urc;
unsigned long where = frame.pc;