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

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>
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>

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 50b30ff..a4c1346 100644 (file)
--- 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;
        }