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arm64: debug: Don't propagate UNKNOWN FAR into si_code for debug signals

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FAR_EL1 is UNKNOWN for all debug exceptions other than those caused by
taking a hardware watchpoint. Unfortunately, if a debug handler returns
a non-zero value, then we will propagate the UNKNOWN FAR value to
userspace via the si_addr field of the SIGTRAP siginfo_t.

Instead, let's set si_addr to take on the PC of the faulting instruction,
which we have available in the current pt_regs.

Cc: <stable@vger.kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Will Deacon 2019-03-01 13:28:00 +00:00 committed by Catalin Marinas
parent 3cd0ddb3de
commit b9a4b9d084
1 changed files with 5 additions and 4 deletions
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9
arch/arm64/mm/fault.c
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@ -824,11 +824,12 @@ void __init hook_debug_fault_code(int nr,
debug_fault_info[nr].name = name;
}
asmlinkage int __exception do_debug_exception(unsigned long addr,
asmlinkage int __exception do_debug_exception(unsigned long addr_if_watchpoint,
unsigned int esr,
struct pt_regs *regs)
{
const struct fault_info *inf = esr_to_debug_fault_info(esr);
unsigned long pc = instruction_pointer(regs);
int rv;
/*
@ -838,14 +839,14 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
if (interrupts_enabled(regs))
trace_hardirqs_off();
if (user_mode(regs) && !is_ttbr0_addr(instruction_pointer(regs)))
if (user_mode(regs) && !is_ttbr0_addr(pc))
arm64_apply_bp_hardening();
if (!inf->fn(addr, esr, regs)) {
if (!inf->fn(addr_if_watchpoint, esr, regs)) {
rv = 1;
} else {
arm64_notify_die(inf->name, regs,
inf->sig, inf->code, (void __user *)addr, esr);
inf->sig, inf->code, (void __user *)pc, esr);
rv = 0;
}