Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e04a28d4 authored by Will Deacon's avatar Will Deacon
Browse files

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: default avatarYang Shi <yang.shi@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent bcaf669b

arch/arm64/kernel/debug-monitors.c

+22 −26
Original line number Diff line number Diff line
@@ -226,11 +226,28 @@ static int call_step_hook(struct pt_regs *regs, unsigned int esr) 
	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 @@ static int single_step_handler(unsigned long addr, unsigned int esr, 
		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 call_break_hook(struct pt_regs *regs, unsigned int esr) 
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 @@ static int brk_handler(unsigned long addr, unsigned int esr, 


int aarch32_break_handler(struct pt_regs *regs)

{

	siginfo_t info;

	u32 arm_instr;

	u16 thumb_instr;

	bool bp = false;
@@ -359,14 +362,7 @@ int aarch32_break_handler(struct pt_regs *regs) 
	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;

}