ARM: 7473/1: deal with handlerless restarts without leaving the kernel (81783786) · Commits · e / devices / android_kernel_oneplus_sm7250

arch/arm/kernel/entry-common.S

+6 −1

Original line number	Diff line number	Diff line
		@@ -54,7 +54,11 @@ work_pending:
		mov r0, sp @ 'regs'
		mov r2, why @ 'syscall'
		bl do_work_pending
		b no_work_pending
		tst r0, #1
		beq no_work_pending
		ldmia sp, {r0 - r6} @ have to reload r0 - r6
		b local_restart @ ... and off we go

		/*
		* "slow" syscall return path. "why" tells us if this was a real syscall.
		*/
		@@ -396,6 +400,7 @@ ENTRY(vector_swi)
		eor scno, scno, #__NR_SYSCALL_BASE @ check OS number
		#endif

		local_restart:
		ldr r10, [tsk, #TI_FLAGS] @ check for syscall tracing
		stmdb sp!, {r4, r5} @ push fifth and sixth args

arch/arm/kernel/signal.c

+29 −21

Original line number	Diff line number	Diff line
		@@ -569,12 +569,13 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
		* the kernel can handle, and then we build all the user-level signal handling
		* stack-frames in one go after that.
		*/
		static void do_signal(struct pt_regs *regs, int syscall)
		static int do_signal(struct pt_regs *regs, int syscall)
		{
		unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
		struct k_sigaction ka;
		siginfo_t info;
		int signr;
		int restart = 0;

		/*
		* If we were from a system call, check for system call restarting...
		@@ -589,10 +590,12 @@ static void do_signal(struct pt_regs *regs, int syscall)
		* debugger will see the already changed PSW.
		*/
		switch (retval) {
		case -ERESTART_RESTARTBLOCK:
		restart++;
		case -ERESTARTNOHAND:
		case -ERESTARTSYS:
		case -ERESTARTNOINTR:
		case -ERESTART_RESTARTBLOCK:
		restart++;
		regs->ARM_r0 = regs->ARM_ORIG_r0;
		regs->ARM_pc = restart_addr;
		break;
		@@ -604,13 +607,15 @@ static void do_signal(struct pt_regs *regs, int syscall)
		* point the debugger may change all our registers ...
		*/
		signr = get_signal_to_deliver(&info, &ka, regs, NULL);
		if (signr > 0) {
		/*
		* Depending on the signal settings we may need to revert the
		* decision to restart the system call. But skip this if a
		* debugger has chosen to restart at a different PC.
		*/
		if (regs->ARM_pc == restart_addr) {
		if (regs->ARM_pc != restart_addr)
		restart = 0;
		if (signr > 0) {
		if (unlikely(restart)) {
		if (retval == -ERESTARTNOHAND \|\|
		retval == -ERESTART_RESTARTBLOCK
		\|\| (retval == -ERESTARTSYS
		@@ -618,28 +623,23 @@ static void do_signal(struct pt_regs *regs, int syscall)
		regs->ARM_r0 = -EINTR;
		regs->ARM_pc = continue_addr;
		}
		clear_thread_flag(TIF_SYSCALL_RESTARTSYS);
		}

		handle_signal(signr, &ka, &info, regs);
		return;
		return 0;
		}

		if (syscall) {
		/*
		* Handle restarting a different system call. As above,
		* if a debugger has chosen to restart at a different PC,
		* ignore the restart.
		*/
		if (retval == -ERESTART_RESTARTBLOCK
		&& regs->ARM_pc == restart_addr)
		if (unlikely(restart)) {
		if (restart > 1)
		set_thread_flag(TIF_SYSCALL_RESTARTSYS);
		regs->ARM_pc = continue_addr;
		}

		restore_saved_sigmask();
		return restart;
		}

		asmlinkage void
		asmlinkage int
		do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
		{
		do {
		@@ -647,10 +647,17 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
		schedule();
		} else {
		if (unlikely(!user_mode(regs)))
		return;
		return 0;
		local_irq_enable();
		if (thread_flags & _TIF_SIGPENDING) {
		do_signal(regs, syscall);
		if (unlikely(do_signal(regs, syscall))) {
		/*
		* Restart without handlers.
		* Deal with it without leaving
		* the kernel space.
		*/
		return 1;
		}
		syscall = 0;
		} else {
		clear_thread_flag(TIF_NOTIFY_RESUME);
		@@ -660,4 +667,5 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
		local_irq_disable();
		thread_flags = current_thread_info()->flags;
		} while (thread_flags & _TIF_WORK_MASK);
		return 0;
		}