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

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commit b9a4b9d084 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Will Deacon
2019-03-01 13:28:00 +00:00
committed by Chris
parent ae4eded44e
commit 58425db229
1 changed files with 6 additions and 5 deletions
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11
arch/arm64/mm/fault.c
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@@ -787,11 +787,12 @@ 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 = debug_fault_info + DBG_ESR_EVT(esr);
unsigned long pc = instruction_pointer(regs);
struct siginfo info;
int rv;
@@ -802,19 +803,19 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
if (interrupts_enabled(regs))
trace_hardirqs_off();
if (user_mode(regs) && instruction_pointer(regs) > TASK_SIZE)
if (user_mode(regs) && pc > TASK_SIZE)
arm64_apply_bp_hardening();
if (!inf->fn(addr, esr, regs)) {
if (!inf->fn(addr_if_watchpoint, esr, regs)) {
rv = 1;
} else {
pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n",
inf->name, esr, addr);
inf->name, esr, pc);
info.si_signo = inf->sig;
info.si_errno = 0;
info.si_code = inf->code;
info.si_addr = (void __user *)addr;
info.si_addr = (void __user *)pc;
arm64_notify_die("", regs, &info, 0);
rv = 0;
}