arm64: kprobes: Avoid calling kprobes debug handlers explicitly

Kprobes bypasses our debug hook registration code so that it doesn't
get tangled up with recursive debug exceptions from things like lockdep:

  http://lists.infradead.org/pipermail/linux-arm-kernel/2015-February/324385.html

However, since then, (a) the hook list has become RCU protected and (b)
the kprobes hooks were found not to filter out exceptions from userspace
correctly. On top of that, the step handler is invoked directly from
single_step_handler(), which *does* use the debug hook list, so it's
clearly not the end of the world.

For now, have kprobes use the debug hook registration API like everybody
else. We can revisit this in the future if this is found to limit
coverage significantly.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h
index d5a44cf859e94284a1a38990105107fe3de28b2f..21721fbf44e749fdcc892428270daed95c99c4d5 100644 (file)
--- a/arch/arm64/include/asm/kprobes.h
+++ b/arch/arm64/include/asm/kprobes.h
@@ -54,8 +54,6 @@ void arch_remove_kprobe(struct kprobe *);
 int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
 int kprobe_exceptions_notify(struct notifier_block *self,
                             unsigned long val, void *data);
-int kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr);
-int kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr);
 void kretprobe_trampoline(void);
 void __kprobes *trampoline_probe_handler(struct pt_regs *regs);
 

diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 9b3fd7fa5b436357112e6b8df6e407d2053f8c73..f4d8cda8830d832181767d5b3e36a7bb239df939 100644 (file)
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -258,10 +258,6 @@ static int single_step_handler(unsigned long unused, unsigned int esr,
        if (!reinstall_suspended_bps(regs))
                return 0;
 
-#ifdef CONFIG_KPROBES
-       if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
-               handler_found = true;
-#endif
        if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
                handler_found = true;
 
@@ -337,12 +333,6 @@ static int brk_handler(unsigned long unused, unsigned int esr,
 {
        bool handler_found = false;
 
-#ifdef CONFIG_KPROBES
-       if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
-               if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED)
-                       handler_found = true;
-       }
-#endif
        if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
                handler_found = true;
 

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index 7a679caf45856e75c21860aaa7522c080fb48e41..baf97f47aec0a8675fcfe5b5e4edbffbaf0ffcab 100644 (file)
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -439,7 +439,7 @@ kprobe_ss_hit(struct kprobe_ctlblk *kcb, unsigned long addr)
        return DBG_HOOK_ERROR;
 }
 
-int __kprobes
+static int __kprobes
 kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
 {
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
@@ -461,7 +461,11 @@ kprobe_single_step_handler(struct pt_regs *regs, unsigned int esr)
        return retval;
 }
 
-int __kprobes
+static struct step_hook kprobes_step_hook = {
+       .fn = kprobe_single_step_handler,
+};
+
+static int __kprobes
 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
 {
        if (user_mode(regs))
@@ -471,6 +475,11 @@ kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr)
        return DBG_HOOK_HANDLED;
 }
 
+static struct break_hook kprobes_break_hook = {
+       .imm = BRK64_ESR_KPROBES,
+       .fn = kprobe_breakpoint_handler,
+};
+
 /*
  * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
  * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
@@ -599,5 +608,8 @@ int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 
 int __init arch_init_kprobes(void)
 {
+       register_kernel_break_hook(&kprobes_break_hook);
+       register_kernel_step_hook(&kprobes_step_hook);
+
        return 0;
 }