From 955a7ae4415fa6d12a4ca953c9dfd37f6c056736 Mon Sep 17 00:00:00 2001 From: William Cohen Date: Fri, 8 Jul 2016 12:35:52 -0400 Subject: [PATCH] arm64: Add trampoline code for kretprobes 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 Signed-off-by: David A. Long Acked-by: Masami Hiramatsu [catalin.marinas@arm.com: removed unnecessary masking of the PSTATE bits] Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/kprobes.h | 2 + arch/arm64/kernel/asm-offsets.c | 11 +++ arch/arm64/kernel/probes/Makefile | 1 + arch/arm64/kernel/probes/kprobes.c | 5 ++ arch/arm64/kernel/probes/kprobes_trampoline.S | 81 +++++++++++++++++++ 5 files changed, 100 insertions(+) create mode 100644 arch/arm64/kernel/probes/kprobes_trampoline.S diff --git a/arch/arm64/include/asm/kprobes.h b/arch/arm64/include/asm/kprobes.h index 79c9511612b51..61b49150dfa30 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 f8e5d47f08807..03dfa27ccf0f2 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -51,6 +51,17 @@ 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 e184d00ebf017..ce06312e3d349 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 63eb0a14d8e9d..be1f074b57368 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -576,6 +576,11 @@ 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 0000000000000..5d6e7f14638c6 --- /dev/null +++ b/arch/arm64/kernel/probes/kprobes_trampoline.S @@ -0,0 +1,81 @@ +/* + * trampoline entry and return code for kretprobes. + */ + +#include +#include +#include + + .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) -- 2.39.5