Commit da6a9125 authored by William Cohen's avatar William Cohen Committed by Catalin Marinas
Browse files

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: default avatarWilliam Cohen <wcohen@redhat.com>
Signed-off-by: default avatarDavid A. Long <dave.long@linaro.org>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
[catalin.marinas@arm.com: removed unnecessary masking of the PSTATE bits]
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 39a67d49

arch/arm64/include/asm/kprobes.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

arch/arm64/kernel/asm-offsets.c

+11 −0
Original line number Diff line number Diff line
@@ -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

arch/arm64/kernel/probes/Makefile

+1 −0
Original line number Diff line number Diff line 
obj-$(CONFIG_KPROBES)		+= kprobes.o decode-insn.o	\

				   kprobes_trampoline.o		\

				   simulate-insn.o

arch/arm64/kernel/probes/kprobes.c

+5 −0
Original line number Diff line number Diff line
@@ -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;

arch/arm64/kernel/probes/kprobes_trampoline.S

0 → 100644
+81 −0
Original line number Diff line number Diff line 
/*

 * 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)

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