ARM kprobes: special hook for the kprobes breakpoint handler

The kprobes code is already able to cope with reentrant probes, so its
handler must be called outside of the region protected by undef_lock.

If ever this lock is released when handlers are called then this commit
could be reverted.

Signed-off-by: Nicolas Pitre <nico@marvell.com>

diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 450ee2cbfe17ebfca26b856388c25880955f70c5..a22a98c43ca5911e9b8f9328509fbd4b9a973ca3 100644 (file)
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -26,12 +26,6 @@
 #include <asm/traps.h>
 #include <asm/cacheflush.h>
 
-/*
- * This undefined instruction must be unique and
- * reserved solely for kprobes' use.
- */
-#define KPROBE_BREAKPOINT_INSTRUCTION  0xe7f001f8
-
 #define MIN_STACK_SIZE(addr)                           \
        min((unsigned long)MAX_STACK_SIZE,              \
            (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
@@ -206,7 +200,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
        }
 }
 
-static int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
+int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 {
        kprobe_handler(regs);
        return 0;

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 65bb762b2d804fed04730ec6986e9bf88bb16bba..5595fdd75e8200ec0e8d5ea8a54c750ed0398e1f 100644 (file)
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -19,6 +19,7 @@
 #include <linux/kallsyms.h>
 #include <linux/delay.h>
 #include <linux/init.h>
+#include <linux/kprobes.h>
 
 #include <asm/atomic.h>
 #include <asm/cacheflush.h>
@@ -313,6 +314,17 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
                get_user(instr, (u32 __user *)pc);
        }
 
+#ifdef CONFIG_KPROBES
+       /*
+        * It is possible to have recursive kprobes, so we can't call
+        * the kprobe trap handler with the undef_lock held.
+        */
+       if (instr == KPROBE_BREAKPOINT_INSTRUCTION && !user_mode(regs)) {
+               kprobe_trap_handler(regs, instr);
+               return;
+       }
+#endif
+
        spin_lock_irqsave(&undef_lock, flags);
        list_for_each_entry(hook, &undef_hook, node) {
                if ((instr & hook->instr_mask) == hook->instr_val &&

diff --git a/include/asm-arm/kprobes.h b/include/asm-arm/kprobes.h
index 273f37413ee6fd9cd2921775d6803d434a3fabaa..4e7bd32288ae6196a2fa5082173d5510cacd0b7a 100644 (file)
--- a/include/asm-arm/kprobes.h
+++ b/include/asm-arm/kprobes.h
@@ -25,6 +25,12 @@
 #define MAX_INSN_SIZE                  2
 #define MAX_STACK_SIZE                 64      /* 32 would probably be OK */
 
+/*
+ * This undefined instruction must be unique and
+ * reserved solely for kprobes' use.
+ */
+#define KPROBE_BREAKPOINT_INSTRUCTION  0xe7f001f8
+
 #define regs_return_value(regs)                ((regs)->ARM_r0)
 #define flush_insn_slot(p)             do { } while (0)
 #define kretprobe_blacklist_size       0
@@ -55,6 +61,7 @@ struct kprobe_ctlblk {
 
 void arch_remove_kprobe(struct kprobe *);
 
+int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr);
 int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
 int kprobe_exceptions_notify(struct notifier_block *self,
                             unsigned long val, void *data);