[v5,15/16] ARM: add uprobes support

From: "David A. Long" <dave.long@linaro.org>

Using Rabin Vincent's ARM uprobes patches as a base, enable uprobes
support on ARM.

Caveats:

 - Thumb is not supported

Signed-off-by: David A. Long <dave.long@linaro.org>
---
 arch/arm/Kconfig                   |   4 +
 arch/arm/include/asm/ptrace.h      |   6 +
 arch/arm/include/asm/thread_info.h |   5 +-
 arch/arm/include/asm/uprobes.h     |  45 ++++++++
 arch/arm/kernel/Makefile           |   1 +
 arch/arm/kernel/signal.c           |   4 +
 arch/arm/kernel/uprobes-arm.c      | 231 +++++++++++++++++++++++++++++++++++++
 arch/arm/kernel/uprobes.c          | 208 +++++++++++++++++++++++++++++++++
 arch/arm/kernel/uprobes.h          |  35 ++++++
 9 files changed, 538 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm/include/asm/uprobes.h
 create mode 100644 arch/arm/kernel/uprobes-arm.c
 create mode 100644 arch/arm/kernel/uprobes.c
 create mode 100644 arch/arm/kernel/uprobes.h

On Thu, 2014-01-23 at 15:05 -0500, David Long wrote:
> From: "David A. Long" <dave.long@linaro.org>
> 
> Using Rabin Vincent's ARM uprobes patches as a base, enable uprobes
> support on ARM.
> 
> Caveats:
> 
>  - Thumb is not supported
> 
> Signed-off-by: David A. Long <dave.long@linaro.org>

As this is based on Rabin's work, and the new files have his Copyright,
then this patch also needs his 'Signed-off-by'. Rabin, I assume that you
agree?

I have no more comments about this patch, however I have included the
rest of the patch below so Rabin can see it's contents (in case he
doesn't still have the original)...


> ---
>  arch/arm/Kconfig                   |   4 +
>  arch/arm/include/asm/ptrace.h      |   6 +
>  arch/arm/include/asm/thread_info.h |   5 +-
>  arch/arm/include/asm/uprobes.h     |  45 ++++++++
>  arch/arm/kernel/Makefile           |   1 +
>  arch/arm/kernel/signal.c           |   4 +
>  arch/arm/kernel/uprobes-arm.c      | 231 +++++++++++++++++++++++++++++++++++++
>  arch/arm/kernel/uprobes.c          | 208 +++++++++++++++++++++++++++++++++
>  arch/arm/kernel/uprobes.h          |  35 ++++++
>  9 files changed, 538 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm/include/asm/uprobes.h
>  create mode 100644 arch/arm/kernel/uprobes-arm.c
>  create mode 100644 arch/arm/kernel/uprobes.c
>  create mode 100644 arch/arm/kernel/uprobes.h
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index c1f1a7e..fec5a6b 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -203,6 +203,10 @@ config ZONE_DMA
>  config NEED_DMA_MAP_STATE
>         def_bool y
>  
> +config ARCH_SUPPORTS_UPROBES
> +	depends on KPROBES
> +	def_bool y
> +
>  config ARCH_HAS_DMA_SET_COHERENT_MASK
>  	bool
>  
> diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
> index 04c99f3..ee688b0a 100644
> --- a/arch/arm/include/asm/ptrace.h
> +++ b/arch/arm/include/asm/ptrace.h
> @@ -80,6 +80,12 @@ static inline long regs_return_value(struct pt_regs *regs)
>  
>  #define instruction_pointer(regs)	(regs)->ARM_pc
>  
> +static inline void instruction_pointer_set(struct pt_regs *regs,
> +					   unsigned long val)
> +{
> +	instruction_pointer(regs) = val;
> +}
> +
>  #ifdef CONFIG_SMP
>  extern unsigned long profile_pc(struct pt_regs *regs);
>  #else
> diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
> index 71a06b2..f989d7c 100644
> --- a/arch/arm/include/asm/thread_info.h
> +++ b/arch/arm/include/asm/thread_info.h
> @@ -153,6 +153,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
>  #define TIF_SIGPENDING		0
>  #define TIF_NEED_RESCHED	1
>  #define TIF_NOTIFY_RESUME	2	/* callback before returning to user */
> +#define TIF_UPROBE		7
>  #define TIF_SYSCALL_TRACE	8
>  #define TIF_SYSCALL_AUDIT	9
>  #define TIF_SYSCALL_TRACEPOINT	10
> @@ -165,6 +166,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
>  #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
>  #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
>  #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
> +#define _TIF_UPROBE		(1 << TIF_UPROBE)
>  #define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)
>  #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
>  #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
> @@ -178,7 +180,8 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
>  /*
>   * Change these and you break ASM code in entry-common.S
>   */
> -#define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_RESUME)
> +#define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
> +				 _TIF_NOTIFY_RESUME | _TIF_UPROBE)
>  
>  #endif /* __KERNEL__ */
>  #endif /* __ASM_ARM_THREAD_INFO_H */
> diff --git a/arch/arm/include/asm/uprobes.h b/arch/arm/include/asm/uprobes.h
> new file mode 100644
> index 0000000..9472c20
> --- /dev/null
> +++ b/arch/arm/include/asm/uprobes.h
> @@ -0,0 +1,45 @@
> +/*
> + * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
> + *
> + * 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.
> + */
> +
> +#ifndef _ASM_UPROBES_H
> +#define _ASM_UPROBES_H
> +
> +#include <asm/probes.h>
> +#include <asm/opcodes.h>
> +
> +typedef u32 uprobe_opcode_t;
> +
> +#define MAX_UINSN_BYTES		4
> +#define UPROBE_XOL_SLOT_BYTES	64
> +
> +#define UPROBE_SWBP_ARM_INSN	0xe7f001f9
> +#define UPROBE_SS_ARM_INSN	0xe7f001fa
> +#define UPROBE_SWBP_INSN	__opcode_to_mem_arm(UPROBE_SWBP_ARM_INSN)
> +#define UPROBE_SWBP_INSN_SIZE	4
> +
> +struct arch_uprobe_task {
> +	u32 backup;
> +	unsigned long	saved_trap_no;
> +};
> +
> +struct arch_uprobe {
> +	u8 insn[MAX_UINSN_BYTES];
> +	unsigned long ixol[2];
> +	uprobe_opcode_t bpinsn;
> +	bool simulate;
> +	u32 pcreg;
> +	void (*prehandler)(struct arch_uprobe *auprobe,
> +			   struct arch_uprobe_task *autask,
> +			   struct pt_regs *regs);
> +	void (*posthandler)(struct arch_uprobe *auprobe,
> +			    struct arch_uprobe_task *autask,
> +			    struct pt_regs *regs);
> +	struct arch_probes_insn asi;
> +};
> +
> +#endif
> diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> index bb739f2..a766bcb 100644
> --- a/arch/arm/kernel/Makefile
> +++ b/arch/arm/kernel/Makefile
> @@ -50,6 +50,7 @@ obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o insn.o
>  obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o insn.o
>  obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o insn.o patch.o
>  obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
> +obj-$(CONFIG_UPROBES)		+= probes.o probes-arm.o uprobes.o uprobes-arm.o
>  obj-$(CONFIG_KPROBES)		+= probes.o kprobes.o kprobes-common.o patch.o
>  ifdef CONFIG_THUMB2_KERNEL
>  obj-$(CONFIG_KPROBES)		+= kprobes-thumb.o probes-thumb.o
> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
> index 04d6388..bd19834 100644
> --- a/arch/arm/kernel/signal.c
> +++ b/arch/arm/kernel/signal.c
> @@ -13,6 +13,7 @@
>  #include <linux/personality.h>
>  #include <linux/uaccess.h>
>  #include <linux/tracehook.h>
> +#include <linux/uprobes.h>
>  
>  #include <asm/elf.h>
>  #include <asm/cacheflush.h>
> @@ -590,6 +591,9 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
>  					return restart;
>  				}
>  				syscall = 0;
> +			} else if (thread_flags & _TIF_UPROBE) {
> +				clear_thread_flag(TIF_UPROBE);
> +				uprobe_notify_resume(regs);
>  			} else {
>  				clear_thread_flag(TIF_NOTIFY_RESUME);
>  				tracehook_notify_resume(regs);
> diff --git a/arch/arm/kernel/uprobes-arm.c b/arch/arm/kernel/uprobes-arm.c
> new file mode 100644
> index 0000000..d5feb50
> --- /dev/null
> +++ b/arch/arm/kernel/uprobes-arm.c
> @@ -0,0 +1,231 @@
> +/*
> + * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
> + *
> + * 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.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/wait.h>
> +#include <linux/uprobes.h>
> +#include <linux/module.h>
> +
> +#include "probes.h"
> +#include "probes-arm.h"
> +#include "uprobes.h"
> +
> +static int uprobes_substitute_pc(unsigned long *pinsn, u32 oregs)
> +{
> +	probes_opcode_t insn = __mem_to_opcode_arm(*pinsn);
> +	probes_opcode_t temp;
> +	probes_opcode_t mask;
> +	int freereg;
> +	u32 free = 0xffff;
> +	u32 regs;
> +
> +	for (regs = oregs; regs; regs >>= 4, insn >>= 4) {
> +		if ((regs & 0xf) == REG_TYPE_NONE)
> +			continue;
> +
> +		free &= ~(1 << (insn & 0xf));
> +	}
> +
> +	/* No PC, no problem */
> +	if (free & (1 << 15))
> +		return 15;
> +
> +	if (!free)
> +		return -1;
> +
> +	/*
> +	 * fls instead of ffs ensures that for "ldrd r0, r1, [pc]" we would
> +	 * pick LR instead of R1.
> +	 */
> +	freereg = free = fls(free) - 1;
> +
> +	temp = __mem_to_opcode_arm(*pinsn);
> +	insn = temp;
> +	regs = oregs;
> +	mask = 0xf;
> +
> +	for (; regs; regs >>= 4, mask <<= 4, free <<= 4, temp >>= 4) {
> +		if ((regs & 0xf) == REG_TYPE_NONE)
> +			continue;
> +
> +		if ((temp & 0xf) != 15)
> +			continue;
> +
> +		insn &= ~mask;
> +		insn |= free & mask;
> +	}
> +
> +	*pinsn = __opcode_to_mem_arm(insn);
> +	return freereg;
> +}
> +
> +static void uprobe_set_pc(struct arch_uprobe *auprobe,
> +			  struct arch_uprobe_task *autask,
> +			  struct pt_regs *regs)
> +{
> +	u32 pcreg = auprobe->pcreg;
> +
> +	autask->backup = regs->uregs[pcreg];
> +	regs->uregs[pcreg] = regs->ARM_pc + 8;
> +}
> +
> +static void uprobe_unset_pc(struct arch_uprobe *auprobe,
> +			    struct arch_uprobe_task *autask,
> +			    struct pt_regs *regs)
> +{
> +	/* PC will be taken care of by common code */
> +	regs->uregs[auprobe->pcreg] = autask->backup;
> +}
> +
> +static void uprobe_aluwrite_pc(struct arch_uprobe *auprobe,
> +			       struct arch_uprobe_task *autask,
> +			       struct pt_regs *regs)
> +{
> +	u32 pcreg = auprobe->pcreg;
> +
> +	alu_write_pc(regs->uregs[pcreg], regs);
> +	regs->uregs[pcreg] = autask->backup;
> +}
> +
> +static void uprobe_write_pc(struct arch_uprobe *auprobe,
> +			    struct arch_uprobe_task *autask,
> +			    struct pt_regs *regs)
> +{
> +	u32 pcreg = auprobe->pcreg;
> +
> +	load_write_pc(regs->uregs[pcreg], regs);
> +	regs->uregs[pcreg] = autask->backup;
> +}
> +
> +enum probes_insn
> +decode_pc_ro(probes_opcode_t insn, struct arch_probes_insn *asi,
> +	     struct decode_header *d)
> +{
> +	struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
> +						   asi);
> +	struct decode_emulate *decode = (struct decode_emulate *) d;
> +	u32 regs = decode->header.type_regs.bits >> DECODE_TYPE_BITS;
> +	int reg;
> +
> +	reg = uprobes_substitute_pc(&auprobe->ixol[0], regs);
> +	if (reg == 15)
> +		return INSN_GOOD;
> +
> +	if (reg == -1)
> +		return INSN_REJECTED;
> +
> +	auprobe->pcreg = reg;
> +	auprobe->prehandler = uprobe_set_pc;
> +	auprobe->posthandler = uprobe_unset_pc;
> +
> +	return INSN_GOOD;
> +}
> +
> +enum probes_insn
> +decode_wb_pc(probes_opcode_t insn, struct arch_probes_insn *asi,
> +	     struct decode_header *d, bool alu)
> +{
> +	struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
> +						   asi);
> +	enum probes_insn ret = decode_pc_ro(insn, asi, d);
> +
> +	if (((insn >> 12) & 0xf) == 15)
> +		auprobe->posthandler = alu ? uprobe_aluwrite_pc
> +					   : uprobe_write_pc;
> +
> +	return ret;
> +}
> +
> +enum probes_insn
> +decode_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
> +			      struct arch_probes_insn *asi,
> +			      struct decode_header *d)
> +{
> +	return decode_wb_pc(insn, asi, d, true);
> +}
> +
> +enum probes_insn
> +decode_ldr(probes_opcode_t insn, struct arch_probes_insn *asi,
> +	   struct decode_header *d)
> +{
> +	return decode_wb_pc(insn, asi, d, false);
> +}
> +
> +enum probes_insn
> +uprobe_decode_ldmstm(probes_opcode_t insn,
> +		     struct arch_probes_insn *asi, struct decode_header *d)
> +{
> +	struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
> +						   asi);
> +	unsigned reglist = insn & 0xffff;
> +	int rn = (insn >> 16) & 0xf;
> +	int lbit = insn & (1 << 20);
> +	unsigned used = reglist | (1 << rn);
> +
> +	if (rn == 15)
> +		return INSN_REJECTED;
> +
> +	if (!(used & (1 << 15)))
> +		return INSN_GOOD;
> +
> +	if (used & (1 << 14))
> +		return INSN_REJECTED;
> +
> +	/* Use LR instead of PC */
> +	insn ^= 0xc000;
> +
> +	auprobe->pcreg = 14;
> +	auprobe->ixol[0] = __opcode_to_mem_arm(insn);
> +
> +	auprobe->prehandler = uprobe_set_pc;
> +	if (lbit)
> +		auprobe->posthandler = uprobe_write_pc;
> +	else
> +		auprobe->posthandler = uprobe_unset_pc;
> +
> +	return INSN_GOOD;
> +}
> +
> +const union decode_action uprobes_probes_actions[] = {
> +	[PROBES_EMULATE_NONE] = {.handler = probes_simulate_nop},
> +	[PROBES_SIMULATE_NOP] = {.handler = probes_simulate_nop},
> +	[PROBES_PRELOAD_IMM] = {.handler = probes_simulate_nop},
> +	[PROBES_PRELOAD_REG] = {.handler = probes_simulate_nop},
> +	[PROBES_BRANCH_IMM] = {.handler = simulate_blx1},
> +	[PROBES_MRS] = {.handler = simulate_mrs},
> +	[PROBES_BRANCH_REG] = {.handler = simulate_blx2bx},
> +	[PROBES_CLZ] = {.handler = probes_simulate_nop},
> +	[PROBES_SATURATING_ARITHMETIC] = {.handler = probes_simulate_nop},
> +	[PROBES_MUL1] = {.handler = probes_simulate_nop},
> +	[PROBES_MUL2] = {.handler = probes_simulate_nop},
> +	[PROBES_SWP] = {.handler = probes_simulate_nop},
> +	[PROBES_LDRSTRD] = {.decoder = decode_pc_ro},
> +	[PROBES_LOAD_EXTRA] = {.decoder = decode_pc_ro},
> +	[PROBES_LOAD] = {.decoder = decode_ldr},
> +	[PROBES_STORE_EXTRA] = {.decoder = decode_pc_ro},
> +	[PROBES_STORE] = {.decoder = decode_pc_ro},
> +	[PROBES_MOV_IP_SP] = {.handler = simulate_mov_ipsp},
> +	[PROBES_DATA_PROCESSING_REG] = {
> +		.decoder = decode_rd12rn16rm0rs8_rwflags},
> +	[PROBES_DATA_PROCESSING_IMM] = {
> +		.decoder = decode_rd12rn16rm0rs8_rwflags},
> +	[PROBES_MOV_HALFWORD] = {.handler = probes_simulate_nop},
> +	[PROBES_SEV] = {.handler = probes_simulate_nop},
> +	[PROBES_WFE] = {.handler = probes_simulate_nop},
> +	[PROBES_SATURATE] = {.handler = probes_simulate_nop},
> +	[PROBES_REV] = {.handler = probes_simulate_nop},
> +	[PROBES_MMI] = {.handler = probes_simulate_nop},
> +	[PROBES_PACK] = {.handler = probes_simulate_nop},
> +	[PROBES_EXTEND] = {.handler = probes_simulate_nop},
> +	[PROBES_EXTEND_ADD] = {.handler = probes_simulate_nop},
> +	[PROBES_MUL_ADD_LONG] = {.handler = probes_simulate_nop},
> +	[PROBES_MUL_ADD] = {.handler = probes_simulate_nop},
> +	[PROBES_BITFIELD] = {.handler = probes_simulate_nop},
> +	[PROBES_BRANCH] = {.handler = simulate_bbl},
> +	[PROBES_LDMSTM] = {.decoder = uprobe_decode_ldmstm}
> +};
> diff --git a/arch/arm/kernel/uprobes.c b/arch/arm/kernel/uprobes.c
> new file mode 100644
> index 0000000..bfe08ba2
> --- /dev/null
> +++ b/arch/arm/kernel/uprobes.c
> @@ -0,0 +1,208 @@
> +/*
> + * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
> + *
> + * 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.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/highmem.h>
> +#include <linux/sched.h>
> +#include <linux/uprobes.h>
> +#include <linux/notifier.h>
> +
> +#include <asm/opcodes.h>
> +#include <asm/traps.h>
> +
> +#include "probes.h"
> +#include "probes-arm.h"
> +#include "uprobes.h"
> +
> +#define UPROBE_TRAP_NR	UINT_MAX
> +
> +bool is_swbp_insn(uprobe_opcode_t *insn)
> +{
> +	return (__mem_to_opcode_arm(*insn) & 0x0fffffff) ==
> +		(UPROBE_SWBP_ARM_INSN & 0x0fffffff);
> +}
> +
> +int set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm,
> +	     unsigned long vaddr)
> +{
> +	return uprobe_write_opcode(mm, vaddr,
> +		   __opcode_to_mem_arm(auprobe->bpinsn));
> +}
> +
> +bool arch_uprobe_ignore(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> +	if (!auprobe->asi.insn_check_cc(regs->ARM_cpsr)) {
> +		regs->ARM_pc += 4;
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> +	probes_opcode_t opcode;
> +
> +	if (!auprobe->simulate)
> +		return false;
> +
> +	opcode = __mem_to_opcode_arm(*(unsigned int *) auprobe->insn);
> +
> +	auprobe->asi.insn_singlestep(opcode, &auprobe->asi, regs);
> +
> +	return true;
> +}
> +
> +unsigned long
> +arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
> +				  struct pt_regs *regs)
> +{
> +	unsigned long orig_ret_vaddr;
> +
> +	orig_ret_vaddr = regs->ARM_lr;
> +	/* Replace the return addr with trampoline addr */
> +	regs->ARM_lr = trampoline_vaddr;
> +	return orig_ret_vaddr;
> +}
> +
> +int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
> +			     unsigned long addr)
> +{
> +	unsigned int insn;
> +	unsigned int bpinsn;
> +	enum probes_insn ret;
> +
> +	/* Thumb not yet support */
> +	if (addr & 0x3)
> +		return -EINVAL;
> +
> +	insn = __mem_to_opcode_arm(*(unsigned int *)auprobe->insn);
> +	auprobe->ixol[0] = __opcode_to_mem_arm(insn);
> +	auprobe->ixol[1] = __opcode_to_mem_arm(UPROBE_SS_ARM_INSN);
> +
> +	ret = arm_probes_decode_insn(insn, &auprobe->asi, false,
> +				     uprobes_probes_actions);
> +	switch (ret) {
> +	case INSN_REJECTED:
> +		return -EINVAL;
> +
> +	case INSN_GOOD_NO_SLOT:
> +		auprobe->simulate = true;
> +		break;
> +
> +	case INSN_GOOD:
> +	default:
> +		break;
> +	}
> +
> +	bpinsn = UPROBE_SWBP_ARM_INSN & 0x0fffffff;
> +	if (insn >= 0xe0000000)
> +		bpinsn |= 0xe0000000;  /* Unconditional instruction */
> +	else
> +		bpinsn |= insn & 0xf0000000;  /* Copy condition from insn */
> +
> +	auprobe->bpinsn = bpinsn;
> +
> +	return 0;
> +}
> +
> +int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> +	struct uprobe_task *utask = current->utask;
> +
> +	if (auprobe->prehandler)
> +		auprobe->prehandler(auprobe, &utask->autask, regs);
> +
> +	utask->autask.saved_trap_no = current->thread.trap_no;
> +	current->thread.trap_no = UPROBE_TRAP_NR;
> +	regs->ARM_pc = utask->xol_vaddr;
> +
> +	return 0;
> +}
> +
> +int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> +	struct uprobe_task *utask = current->utask;
> +
> +	WARN_ON_ONCE(current->thread.trap_no != UPROBE_TRAP_NR);
> +
> +	current->thread.trap_no = utask->autask.saved_trap_no;
> +	regs->ARM_pc = utask->vaddr + 4;
> +
> +	if (auprobe->posthandler)
> +		auprobe->posthandler(auprobe, &utask->autask, regs);
> +
> +	return 0;
> +}
> +
> +bool arch_uprobe_xol_was_trapped(struct task_struct *t)
> +{
> +	if (t->thread.trap_no != UPROBE_TRAP_NR)
> +		return true;
> +
> +	return false;
> +}
> +
> +void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> +	struct uprobe_task *utask = current->utask;
> +
> +	current->thread.trap_no = utask->autask.saved_trap_no;
> +	instruction_pointer_set(regs, utask->vaddr);
> +}
> +
> +int arch_uprobe_exception_notify(struct notifier_block *self,
> +				 unsigned long val, void *data)
> +{
> +	return NOTIFY_DONE;
> +}
> +
> +static int uprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
> +{
> +	unsigned long flags;
> +
> +	local_irq_save(flags);
> +	instr &= 0x0fffffff;
> +	if (instr == (UPROBE_SWBP_ARM_INSN & 0x0fffffff))
> +		uprobe_pre_sstep_notifier(regs);
> +	else if (instr == (UPROBE_SS_ARM_INSN & 0x0fffffff))
> +		uprobe_post_sstep_notifier(regs);
> +	local_irq_restore(flags);
> +
> +	return 0;
> +}
> +
> +unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
> +{
> +	return instruction_pointer(regs);
> +}
> +
> +static struct undef_hook uprobes_arm_break_hook = {
> +	.instr_mask	= 0x0fffffff,
> +	.instr_val	= (UPROBE_SWBP_ARM_INSN & 0x0fffffff),
> +	.cpsr_mask	= MODE_MASK,
> +	.cpsr_val	= USR_MODE,
> +	.fn		= uprobe_trap_handler,
> +};
> +
> +static struct undef_hook uprobes_arm_ss_hook = {
> +	.instr_mask	= 0x0fffffff,
> +	.instr_val	= (UPROBE_SS_ARM_INSN & 0x0fffffff),
> +	.cpsr_mask	= MODE_MASK,
> +	.cpsr_val	= USR_MODE,
> +	.fn		= uprobe_trap_handler,
> +};
> +
> +static int arch_uprobes_init(void)
> +{
> +	register_undef_hook(&uprobes_arm_break_hook);
> +	register_undef_hook(&uprobes_arm_ss_hook);
> +
> +	return 0;
> +}
> +device_initcall(arch_uprobes_init);
> diff --git a/arch/arm/kernel/uprobes.h b/arch/arm/kernel/uprobes.h
> new file mode 100644
> index 0000000..a6581f5
> --- /dev/null
> +++ b/arch/arm/kernel/uprobes.h
> @@ -0,0 +1,35 @@
> +/*
> + * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
> + *
> + * 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.
> + */
> +
> +#ifndef __ARM_KERNEL_UPROBES_H
> +#define __ARM_KERNEL_UPROBES_H
> +
> +enum probes_insn uprobe_decode_ldmstm(probes_opcode_t insn,
> +				      struct arch_probes_insn *asi,
> +				      struct decode_header *d);
> +
> +enum probes_insn decode_ldr(probes_opcode_t insn,
> +			    struct arch_probes_insn *asi,
> +			    struct decode_header *d);
> +
> +enum probes_insn
> +decode_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
> +			      struct arch_probes_insn *asi,
> +			      struct decode_header *d);
> +
> +enum probes_insn
> +decode_wb_pc(probes_opcode_t insn, struct arch_probes_insn *asi,
> +	     struct decode_header *d, bool alu);
> +
> +enum probes_insn
> +decode_pc_ro(probes_opcode_t insn, struct arch_probes_insn *asi,
> +	     struct decode_header *d);
> +
> +extern const union decode_action uprobes_probes_actions[];
> +
> +#endif


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