diff options
| -rw-r--r-- | arch/arm64/kernel/probes/kprobes.c | 29 |
1 files changed, 13 insertions, 16 deletions
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index c6b0f40620d8..0354ffeb2ed5 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -166,13 +166,18 @@ static void __kprobes set_current_kprobe(struct kprobe *p) } /* - * The D-flag (Debug mask) is set (masked) upon debug exception entry. - * Kprobes needs to clear (unmask) D-flag -ONLY- in case of recursive - * probe i.e. when probe hit from kprobe handler context upon - * executing the pre/post handlers. In this case we return with - * D-flag clear so that single-stepping can be carried-out. - * - * Leave D-flag set in all other cases. + * When PSTATE.D is set (masked), then software step exceptions can not be + * generated. + * SPSR's D bit shows the value of PSTATE.D immediately before the + * exception was taken. PSTATE.D is set while entering into any exception + * mode, however software clears it for any normal (none-debug-exception) + * mode in the exception entry. Therefore, when we are entering into kprobe + * breakpoint handler from any normal mode then SPSR.D bit is already + * cleared, however it is set when we are entering from any debug exception + * mode. + * Since we always need to generate single step exception after a kprobe + * breakpoint exception therefore we need to clear it unconditionally, when + * we become sure that the current breakpoint exception is for kprobe. */ static void __kprobes spsr_set_debug_flag(struct pt_regs *regs, int mask) @@ -245,10 +250,7 @@ static void __kprobes setup_singlestep(struct kprobe *p, set_ss_context(kcb, slot); /* mark pending ss */ - if (kcb->kprobe_status == KPROBE_REENTER) - spsr_set_debug_flag(regs, 0); - else - WARN_ON(regs->pstate & PSR_D_BIT); + spsr_set_debug_flag(regs, 0); /* IRQs and single stepping do not mix well. */ kprobes_save_local_irqflag(kcb, regs); @@ -333,8 +335,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) BUG(); kernel_disable_single_step(); - if (kcb->kprobe_status == KPROBE_REENTER) - spsr_set_debug_flag(regs, 1); if (kcb->kprobe_status == KPROBE_REENTER) restore_previous_kprobe(kcb); @@ -457,9 +457,6 @@ kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr) kprobes_restore_local_irqflag(kcb, regs); kernel_disable_single_step(); - if (kcb->kprobe_status == KPROBE_REENTER) - spsr_set_debug_flag(regs, 1); - post_kprobe_handler(kcb, regs); } |