Commit cc73cc6b authored by Tiezhu Yang's avatar Tiezhu Yang Committed by Huacai Chen
Browse files

LoongArch: Make do_xyz() exception handlers more robust 



Currently, interrupts need to be disabled before single-step mode is
set, it requires that CSR_PRMD_PIE be cleared in save_local_irqflag()
which is called by setup_singlestep(), this is reasonable.

But in the first kprobe breakpoint exception, if the irq is enabled at
the beginning of do_bp(), it will not be disabled at the end of do_bp()
due to the CSR_PRMD_PIE has been cleared in save_local_irqflag(). So for
this case, it may corrupt exception context when restoring the exception
after do_bp() in handle_bp(), this is not reasonable.

In order to restore exception safely in handle_bp(), it needs to ensure
the irq is disabled at the end of do_bp(), so just add a local variable
to record the original interrupt status in the parent context, then use
it as the check condition to enable and disable irq in do_bp().

While at it, do the similar thing for other do_xyz() exception handlers
to make them more robust.

Fixes: 6d4cc40f ("LoongArch: Add kprobes support")
Suggested-by: default avatarJinyang He <hejinyang@loongson.cn>
Suggested-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
Co-developed-by: default avatarTianyang Zhang <zhangtianyang@loongson.cn>
Signed-off-by: default avatarTianyang Zhang <zhangtianyang@loongson.cn>
Signed-off-by: default avatarTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent bb0511d5

arch/loongarch/kernel/traps.c

+12 −8
Original line number Diff line number Diff line
@@ -553,9 +553,10 @@ asmlinkage void noinstr do_ale(struct pt_regs *regs) 
	die_if_kernel("Kernel ale access", regs);

	force_sig_fault(SIGBUS, BUS_ADRALN, (void __user *)regs->csr_badvaddr);

#else

	bool pie = regs_irqs_disabled(regs);

	unsigned int *pc;



	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_enable();



	perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, regs->csr_badvaddr);
@@ -582,7 +583,7 @@ asmlinkage void noinstr do_ale(struct pt_regs *regs) 
	die_if_kernel("Kernel ale access", regs);

	force_sig_fault(SIGBUS, BUS_ADRALN, (void __user *)regs->csr_badvaddr);

out:

	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_disable();

#endif

	irqentry_exit(regs, state);
@@ -621,12 +622,13 @@ static void bug_handler(struct pt_regs *regs) 
asmlinkage void noinstr do_bce(struct pt_regs *regs)

{

	bool user = user_mode(regs);

	bool pie = regs_irqs_disabled(regs);

	unsigned long era = exception_era(regs);

	u64 badv = 0, lower = 0, upper = ULONG_MAX;

	union loongarch_instruction insn;

	irqentry_state_t state = irqentry_enter(regs);



	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_enable();



	current->thread.trap_nr = read_csr_excode();
@@ -692,7 +694,7 @@ asmlinkage void noinstr do_bce(struct pt_regs *regs) 
	force_sig_bnderr((void __user *)badv, (void __user *)lower, (void __user *)upper);



out:

	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_disable();



	irqentry_exit(regs, state);
@@ -710,11 +712,12 @@ asmlinkage void noinstr do_bce(struct pt_regs *regs) 
asmlinkage void noinstr do_bp(struct pt_regs *regs)

{

	bool user = user_mode(regs);

	bool pie = regs_irqs_disabled(regs);

	unsigned int opcode, bcode;

	unsigned long era = exception_era(regs);

	irqentry_state_t state = irqentry_enter(regs);



	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_enable();



	if (__get_inst(&opcode, (u32 *)era, user))
@@ -780,7 +783,7 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs) 
	}



out:

	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_disable();



	irqentry_exit(regs, state);
@@ -1015,6 +1018,7 @@ static void init_restore_lbt(void) 


asmlinkage void noinstr do_lbt(struct pt_regs *regs)

{

	bool pie = regs_irqs_disabled(regs);

	irqentry_state_t state = irqentry_enter(regs);



	/*
@@ -1024,7 +1028,7 @@ asmlinkage void noinstr do_lbt(struct pt_regs *regs) 
	 * (including the user using 'MOVGR2GCSR' to turn on TM, which

	 * will not trigger the BTE), we need to check PRMD first.

	 */

	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_enable();



	if (!cpu_has_lbt) {
@@ -1038,7 +1042,7 @@ asmlinkage void noinstr do_lbt(struct pt_regs *regs) 
	preempt_enable();



out:

	if (regs->csr_prmd & CSR_PRMD_PIE)

	if (!pie)

		local_irq_disable();



	irqentry_exit(regs, state);