On Thu, Oct 17, 2013 at 12:17:48PM +0100, Sandeepa Prabhu wrote:
Add support for AArch64 instruction simulation in kprobes.
Kprobes need simulation of instructions that cannot be stepped right-away from different memory location. i.e. those instructions that uses PC-relative addressing. In simulation, the behaviour of the instruction is implemented using copy of pt_regs.
Following instruction catagories are simulated:
- All branching instructions(conditional, register, and immediate)
- Literal access instructions(load-literal, adr/adrp)
conditional execution are limited to branching instructions in ARM v8. If conditions at PSTATE does not match the condition fields of opcode, the instruction is effectively NOP. Kprobes consider this case as 'miss'.
[...]
diff --git a/arch/arm64/kernel/kprobes-arm64.c b/arch/arm64/kernel/kprobes-arm64.c index 30d1c14..c690be3 100644 --- a/arch/arm64/kernel/kprobes-arm64.c +++ b/arch/arm64/kernel/kprobes-arm64.c @@ -20,6 +20,101 @@
#include "probes-decode.h" #include "kprobes-arm64.h" +#include "simulate-insn.h"
+/*
- condition check functions for kprobes simulation
- */
+static unsigned long __kprobes +__check_pstate(struct kprobe *p, struct pt_regs *regs) +{
struct arch_specific_insn *asi = &p->ainsn;unsigned long pstate = regs->pstate & 0xffffffff;return asi->pstate_cc(pstate);+}
+static unsigned long __kprobes +__check_cbz(struct kprobe *p, struct pt_regs *regs) +{
return check_cbz((u32)p->opcode, regs);
Isn't p->opcode already a u32? (by your definition of kprobe_opcode_t).
diff --git a/arch/arm64/kernel/simulate-insn.c b/arch/arm64/kernel/simulate-insn.c new file mode 100644 index 0000000..10173cf --- /dev/null +++ b/arch/arm64/kernel/simulate-insn.c @@ -0,0 +1,184 @@ +/*
- arch/arm64/kernel/simulate-insn.c
- Copyright (C) 2013 Linaro Limited.
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License version 2 as
- published by the Free Software Foundation.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- General Public License for more details.
- */
+#include <linux/kernel.h> +#include <linux/kprobes.h> +#include <linux/module.h>
+#include "simulate-insn.h"
+#define sign_extend(x, signbit) \
((x) | (0 - ((x) & (1 << (signbit)))))+#define bbl_displacement(insn) \
sign_extend(((insn) & 0x3ffffff) << 2, 27)+#define bcond_displacement(insn) \
sign_extend(((insn >> 5) & 0xfffff) << 2, 21)+#define cbz_displacement(insn) \
sign_extend(((insn >> 5) & 0xfffff) << 2, 21)+#define tbz_displacement(insn) \
sign_extend(((insn >> 5) & 0x3fff) << 2, 15)+#define ldr_displacement(insn) \
sign_extend(((insn >> 5) & 0xfffff) << 2, 21)
The mask, shift and signbit position are all related here, so you could rework the definition of sign_extend to avoid having three magic numbers.
Will