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authorWilliam Cohen <wcohen@redhat.com>2016-07-08 12:35:52 -0400
committerAlex Shi <alex.shi@linaro.org>2016-10-20 15:38:13 +0800
commitaecc244b48b51e2ce0f1fefd3111ba6d6548d0ce (patch)
treecb9d3864f6b3ae52cbf61659209651a4c1bf20eb
parent1f4a59d0e95a8b5a1a3e35080b4e6b579d6b2f52 (diff)
downloadlinux-linaro-stable-aecc244b48b51e2ce0f1fefd3111ba6d6548d0ce.tar.gz
arm64: Add trampoline code for kretprobes
commit da6a91252ad98d49b49e83b76c1f032cdf6e5258 upstream. The trampoline code is used by kretprobes to capture a return from a probed function. This is done by saving the registers, calling the handler, and restoring the registers. The code then returns to the original saved caller return address. It is necessary to do this directly instead of using a software breakpoint because the code used in processing that breakpoint could itself be kprobe'd and cause a problematic reentry into the debug exception handler. Signed-off-by: William Cohen <wcohen@redhat.com> Signed-off-by: David A. Long <dave.long@linaro.org> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> [catalin.marinas@arm.com: removed unnecessary masking of the PSTATE bits] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/include/asm/kprobes.h2
-rw-r--r--arch/arm64/kernel/asm-offsets.c11
-rw-r--r--arch/arm64/kernel/probes/Makefile1
-rw-r--r--arch/arm64/kernel/probes/kprobes.c5
-rw-r--r--arch/arm64/kernel/probes/kprobes_trampoline.S81
5 files changed, 100 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h
index 79c9511612b5..61b49150dfa3 100644
--- a/arch/arm64/include/asm/kprobes.h
+++ b/arch/arm64/include/asm/kprobes.h
@@ -56,5 +56,7 @@ 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);
#endif /* _ARM_KPROBES_H */
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 087cf9a65359..dd2925192405 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -49,6 +49,17 @@ int main(void)
DEFINE(S_X5, offsetof(struct pt_regs, regs[5]));
DEFINE(S_X6, offsetof(struct pt_regs, regs[6]));
DEFINE(S_X7, offsetof(struct pt_regs, regs[7]));
+ DEFINE(S_X8, offsetof(struct pt_regs, regs[8]));
+ DEFINE(S_X10, offsetof(struct pt_regs, regs[10]));
+ DEFINE(S_X12, offsetof(struct pt_regs, regs[12]));
+ DEFINE(S_X14, offsetof(struct pt_regs, regs[14]));
+ DEFINE(S_X16, offsetof(struct pt_regs, regs[16]));
+ DEFINE(S_X18, offsetof(struct pt_regs, regs[18]));
+ DEFINE(S_X20, offsetof(struct pt_regs, regs[20]));
+ DEFINE(S_X22, offsetof(struct pt_regs, regs[22]));
+ DEFINE(S_X24, offsetof(struct pt_regs, regs[24]));
+ DEFINE(S_X26, offsetof(struct pt_regs, regs[26]));
+ DEFINE(S_X28, offsetof(struct pt_regs, regs[28]));
DEFINE(S_LR, offsetof(struct pt_regs, regs[30]));
DEFINE(S_SP, offsetof(struct pt_regs, sp));
#ifdef CONFIG_COMPAT
diff --git a/arch/arm64/kernel/probes/Makefile b/arch/arm64/kernel/probes/Makefile
index e184d00ebf01..ce06312e3d34 100644
--- a/arch/arm64/kernel/probes/Makefile
+++ b/arch/arm64/kernel/probes/Makefile
@@ -1,2 +1,3 @@
obj-$(CONFIG_KPROBES) += kprobes.o decode-insn.o \
+ kprobes_trampoline.o \
simulate-insn.o
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index aff80b342382..5619041ac74b 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -565,6 +565,11 @@ bool arch_within_kprobe_blacklist(unsigned long addr)
return false;
}
+void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
+{
+ return NULL;
+}
+
int __init arch_init_kprobes(void)
{
return 0;
diff --git a/arch/arm64/kernel/probes/kprobes_trampoline.S b/arch/arm64/kernel/probes/kprobes_trampoline.S
new file mode 100644
index 000000000000..5d6e7f14638c
--- /dev/null
+++ b/arch/arm64/kernel/probes/kprobes_trampoline.S
@@ -0,0 +1,81 @@
+/*
+ * trampoline entry and return code for kretprobes.
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm-offsets.h>
+#include <asm/assembler.h>
+
+ .text
+
+ .macro save_all_base_regs
+ stp x0, x1, [sp, #S_X0]
+ stp x2, x3, [sp, #S_X2]
+ stp x4, x5, [sp, #S_X4]
+ stp x6, x7, [sp, #S_X6]
+ stp x8, x9, [sp, #S_X8]
+ stp x10, x11, [sp, #S_X10]
+ stp x12, x13, [sp, #S_X12]
+ stp x14, x15, [sp, #S_X14]
+ stp x16, x17, [sp, #S_X16]
+ stp x18, x19, [sp, #S_X18]
+ stp x20, x21, [sp, #S_X20]
+ stp x22, x23, [sp, #S_X22]
+ stp x24, x25, [sp, #S_X24]
+ stp x26, x27, [sp, #S_X26]
+ stp x28, x29, [sp, #S_X28]
+ add x0, sp, #S_FRAME_SIZE
+ stp lr, x0, [sp, #S_LR]
+ /*
+ * Construct a useful saved PSTATE
+ */
+ mrs x0, nzcv
+ mrs x1, daif
+ orr x0, x0, x1
+ mrs x1, CurrentEL
+ orr x0, x0, x1
+ mrs x1, SPSel
+ orr x0, x0, x1
+ stp xzr, x0, [sp, #S_PC]
+ .endm
+
+ .macro restore_all_base_regs
+ ldr x0, [sp, #S_PSTATE]
+ and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT)
+ msr nzcv, x0
+ ldp x0, x1, [sp, #S_X0]
+ ldp x2, x3, [sp, #S_X2]
+ ldp x4, x5, [sp, #S_X4]
+ ldp x6, x7, [sp, #S_X6]
+ ldp x8, x9, [sp, #S_X8]
+ ldp x10, x11, [sp, #S_X10]
+ ldp x12, x13, [sp, #S_X12]
+ ldp x14, x15, [sp, #S_X14]
+ ldp x16, x17, [sp, #S_X16]
+ ldp x18, x19, [sp, #S_X18]
+ ldp x20, x21, [sp, #S_X20]
+ ldp x22, x23, [sp, #S_X22]
+ ldp x24, x25, [sp, #S_X24]
+ ldp x26, x27, [sp, #S_X26]
+ ldp x28, x29, [sp, #S_X28]
+ .endm
+
+ENTRY(kretprobe_trampoline)
+ sub sp, sp, #S_FRAME_SIZE
+
+ save_all_base_regs
+
+ mov x0, sp
+ bl trampoline_probe_handler
+ /*
+ * Replace trampoline address in lr with actual orig_ret_addr return
+ * address.
+ */
+ mov lr, x0
+
+ restore_all_base_regs
+
+ add sp, sp, #S_FRAME_SIZE
+ ret
+
+ENDPROC(kretprobe_trampoline)