From 9b34dffcd943044501d62cedb50c30e01fc3c679 Mon Sep 17 00:00:00 2001 From: Tiezhu Yang Date: Thu, 24 Apr 2025 20:15:41 +0800 Subject: [PATCH] LoongArch: Make do_xyz() exception handlers more robust [ Upstream commit cc73cc6bcdb5f959670e3ff9abdc62461452ddff ] 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: 6d4cc40fb5f5 ("LoongArch: Add kprobes support") Suggested-by: Jinyang He Suggested-by: Huacai Chen Co-developed-by: Tianyang Zhang Signed-off-by: Tianyang Zhang Signed-off-by: Tiezhu Yang Signed-off-by: Huacai Chen Signed-off-by: Sasha Levin --- arch/loongarch/kernel/traps.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c index c57b4134f3e8..00424b7e34c1 100644 --- a/arch/loongarch/kernel/traps.c +++ b/arch/loongarch/kernel/traps.c @@ -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 @@ sigbus: 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); @@ -614,12 +615,13 @@ 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(); @@ -685,7 +687,7 @@ 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); @@ -703,11 +705,12 @@ bad_era: 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)) @@ -773,7 +776,7 @@ 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); @@ -1008,6 +1011,7 @@ 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); /* @@ -1017,7 +1021,7 @@ 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) { @@ -1031,7 +1035,7 @@ 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);