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

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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>
This commit is contained in:
Will Deacon 2019-03-01 13:28:00 +00:00 • committed by Greg Kroah-Hartman
parent 12ae58ca7e
commit a930f8ce20
1 changed files with 5 additions and 4 deletions
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9
arch/arm64/mm/fault.c
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@ -589,11 +589,12 @@ void __init hook_debug_fault_code(int nr,
debug_fault_info[nr].name = name; 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, unsigned int esr,
struct pt_regs *regs) struct pt_regs *regs)
{ {
const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr); const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
unsigned long pc = instruction_pointer(regs);
struct siginfo info; struct siginfo info;
int rv; int rv;
@ -604,16 +605,16 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
if (interrupts_enabled(regs)) if (interrupts_enabled(regs))
trace_hardirqs_off(); trace_hardirqs_off();
if (!inf->fn(addr, esr, regs)) { if (!inf->fn(addr_if_watchpoint, esr, regs)) {
rv = 1; rv = 1;
} else { } else {
pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n", 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_signo = inf->sig;
info.si_errno = 0; info.si_errno = 0;
info.si_code = inf->code; info.si_code = inf->code;
info.si_addr = (void __user *)addr; info.si_addr = (void __user *)pc;
arm64_notify_die("", regs, &info, 0); arm64_notify_die("", regs, &info, 0);
rv = 0; rv = 0;
} }