arm64: debug: re-enable irqs before sending breakpoint SIGTRAP
force_sig_info can sleep under an -rt kernel, so attempting to send a
breakpoint SIGTRAP with interrupts disabled yields the following BUG:
BUG: sleeping function called from invalid context at
/kernel-source/kernel/locking/rtmutex.c:917
in_atomic(): 0, irqs_disabled(): 128, pid: 551, name: test.sh
CPU: 5 PID: 551 Comm: test.sh Not tainted 4.1.13-rt13 #7
Hardware name: Freescale Layerscape 2085a RDB Board (DT)
Call trace:
dump_backtrace+0x0/0x128
show_stack+0x24/0x30
dump_stack+0x80/0xa0
___might_sleep+0x128/0x1a0
rt_spin_lock+0x2c/0x40
force_sig_info+0xcc/0x210
brk_handler.part.2+0x6c/0x80
brk_handler+0xd8/0xe8
do_debug_exception+0x58/0xb8
This patch fixes the problem by ensuring that interrupts are enabled
prior to sending the SIGTRAP if they were already enabled in the user
context.
Reported-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 8aee3ae..c536c9e 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -226,11 +226,28 @@
return retval;
}
+static void send_user_sigtrap(int si_code)
+{
+ struct pt_regs *regs = current_pt_regs();
+ siginfo_t info = {
+ .si_signo = SIGTRAP,
+ .si_errno = 0,
+ .si_code = si_code,
+ .si_addr = (void __user *)instruction_pointer(regs),
+ };
+
+ if (WARN_ON(!user_mode(regs)))
+ return;
+
+ if (interrupts_enabled(regs))
+ local_irq_enable();
+
+ force_sig_info(SIGTRAP, &info, current);
+}
+
static int single_step_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
- siginfo_t info;
-
/*
* If we are stepping a pending breakpoint, call the hw_breakpoint
* handler first.
@@ -239,11 +256,7 @@
return 0;
if (user_mode(regs)) {
- info.si_signo = SIGTRAP;
- info.si_errno = 0;
- info.si_code = TRAP_HWBKPT;
- info.si_addr = (void __user *)instruction_pointer(regs);
- force_sig_info(SIGTRAP, &info, current);
+ send_user_sigtrap(TRAP_HWBKPT);
/*
* ptrace will disable single step unless explicitly
@@ -307,17 +320,8 @@
static int brk_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
- siginfo_t info;
-
if (user_mode(regs)) {
- info = (siginfo_t) {
- .si_signo = SIGTRAP,
- .si_errno = 0,
- .si_code = TRAP_BRKPT,
- .si_addr = (void __user *)instruction_pointer(regs),
- };
-
- force_sig_info(SIGTRAP, &info, current);
+ send_user_sigtrap(TRAP_BRKPT);
} else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
pr_warning("Unexpected kernel BRK exception at EL1\n");
return -EFAULT;
@@ -328,7 +332,6 @@
int aarch32_break_handler(struct pt_regs *regs)
{
- siginfo_t info;
u32 arm_instr;
u16 thumb_instr;
bool bp = false;
@@ -359,14 +362,7 @@
if (!bp)
return -EFAULT;
- info = (siginfo_t) {
- .si_signo = SIGTRAP,
- .si_errno = 0,
- .si_code = TRAP_BRKPT,
- .si_addr = pc,
- };
-
- force_sig_info(SIGTRAP, &info, current);
+ send_user_sigtrap(TRAP_BRKPT);
return 0;
}