@@ -325,6 +325,9 @@ static int brk_handler(unsigned long addr, unsigned int esr,
return -EFAULT;
}
+ if (kernel_active_single_step() || test_thread_flag(TIF_SINGLESTEP))
+ return 1;
+
return 0;
}
NOKPROBE_SYMBOL(brk_handler);
@@ -698,7 +698,7 @@ static int breakpoint_handler(unsigned long unused, unsigned int esr,
}
}
- return 0;
+ return 1;
}
NOKPROBE_SYMBOL(breakpoint_handler);
@@ -843,7 +843,7 @@ static int watchpoint_handler(unsigned long addr, unsigned int esr,
}
}
- return 0;
+ return 1;
}
NOKPROBE_SYMBOL(watchpoint_handler);
@@ -653,6 +653,13 @@ static struct fault_info __refdata debug_fault_info[] = {
{ do_bad, SIGBUS, 0, "unknown 7" },
};
+/*
+ * fn should return 0 from any software breakpoint and hw
+ * breakpoint/watchpoint handler if it does not expect a single step stage
+ * and 1 if it expects single step followed by its execution. A single step
+ * handler should always return 0. All handler should return a -ve error in
+ * any other case.
+ */
void __init hook_debug_fault_code(int nr,
int (*fn)(unsigned long, unsigned int, struct pt_regs *),
int sig, int code, const char *name)
@@ -665,6 +672,8 @@ void __init hook_debug_fault_code(int nr,
debug_fault_info[nr].name = name;
}
+static DEFINE_PER_CPU(bool, irq_enable_needed);
+
asmlinkage int __exception do_debug_exception(unsigned long addr,
unsigned int esr,
struct pt_regs *regs)
@@ -672,6 +681,7 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
struct siginfo info;
int rv;
+ bool *irq_en_needed = this_cpu_ptr(&irq_enable_needed);
/*
* Tell lockdep we disabled irqs in entry.S. Do nothing if they were
@@ -680,9 +690,8 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
if (interrupts_enabled(regs))
trace_hardirqs_off();
- if (!inf->fn(addr, esr, regs)) {
- rv = 1;
- } else {
+ rv = inf->fn(addr, esr, regs);
+ if (rv < 0) {
pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n",
inf->name, esr, addr);
@@ -691,7 +700,12 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
info.si_code = inf->code;
info.si_addr = (void __user *)addr;
arm64_notify_die("", regs, &info, 0);
- rv = 0;
+ } else if (rv == 1 && interrupts_enabled(regs)) {
+ regs->pstate |= PSR_I_BIT;
+ *irq_en_needed = true;
+ } else if (rv == 0 && *irq_en_needed) {
+ regs->pstate &= ~PSR_I_BIT;
+ *irq_en_needed = false;
}
if (interrupts_enabled(regs))
If an interrupt is generated between breakpoint and step handler then step handler can not get correct step address. This situation can easily be invoked by samples/hw_breakpoint/data_breakpoint.c. It can also be reproduced if we insert any printk() statement or dump_stack() in perf overflow_handler. So, it seems that perf is working fine just luckily. If the CPU which is handling perf breakpoint handler receives any interrupt then, perf step handler will not execute sanely. This patch improves do_debug_exception() handling, which enforces now, that exception handler function: - should return 0 for any software breakpoint and hw breakpoint/watchpoint handler if it does not expect a single step stage - should return 1 if it expects single step. - A single step handler should always return 0. - All handler should return a -ve error in any other case. Now, we can know in do_debug_exception() that whether a step exception will be followed or not. If there will a step exception then disable irq. Re-enable it after single step handling. Signed-off-by: Pratyush Anand <panand@redhat.com> --- arch/arm64/kernel/debug-monitors.c | 3 +++ arch/arm64/kernel/hw_breakpoint.c | 4 ++-- arch/arm64/mm/fault.c | 22 ++++++++++++++++++---- 3 files changed, 23 insertions(+), 6 deletions(-)