Commit b9a4b9d084d978f80eb9210727c81804588b42ff 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 # 4.19.y 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 --- arch/arm64/mm/fault.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 50b30ff30de4..a4c134677285 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -827,11 +827,12 @@ 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); int rv;

/* @@ -841,10 +842,10 @@ 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 { struct siginfo info; @@ -853,7 +854,7 @@ asmlinkage int __exception do_debug_exception(unsigned long addr, 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(inf->name, regs, &info, esr); rv = 0; }