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uprobes/core: Clean up, refactor and improve the code
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Make the uprobes code readable to me:

 - improve the Kconfig text so that a mere mortal gets some idea
   what CONFIG_UPROBES=y is really about

 - do trivial renames to standardize around the uprobes_*() namespace

 - clean up and simplify various code flow details

 - separate basic blocks of functionality

 - line break artifact and white space related removal

 - use standard local varible definition blocks

 - use vertical spacing to make things more readable

 - remove unnecessary volatile

 - restructure comment blocks to make them more uniform and
   more readable in general

Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Anton Arapov <anton@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Link: http://lkml.kernel.org/n/tip-ewbwhb8o6navvllsauu7k07p@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Ingo Molnar committed Feb 17, 2012
1 parent 2b14449 commit 7b2d81d
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Showing 6 changed files with 233 additions and 186 deletions.
14 changes: 10 additions & 4 deletions arch/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -66,13 +66,19 @@ config OPTPROBES
depends on !PREEMPT

config UPROBES
bool "User-space probes (EXPERIMENTAL)"
bool "Transparent user-space probes (EXPERIMENTAL)"
depends on ARCH_SUPPORTS_UPROBES
default n
help
Uprobes enables kernel subsystems to establish probepoints
in user applications and execute handler functions when
the probepoints are hit.
Uprobes is the user-space counterpart to kprobes: they
enable instrumentation applications (such as 'perf probe')
to establish unintrusive probes in user-space binaries and
libraries, by executing handler functions when the probes
are hit by user-space applications.

( These probes come in the form of single-byte breakpoints,
managed by the kernel and kept transparent to the probed
application. )

If in doubt, say "N".

Expand Down
17 changes: 9 additions & 8 deletions arch/x86/include/asm/uprobes.h
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
#ifndef _ASM_UPROBES_H
#define _ASM_UPROBES_H
/*
* Userspace Probes (UProbes) for x86
* User-space Probes (UProbes) for x86
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
Expand All @@ -24,19 +24,20 @@
*/

typedef u8 uprobe_opcode_t;
#define MAX_UINSN_BYTES 16
#define UPROBES_XOL_SLOT_BYTES 128 /* to keep it cache aligned */

#define UPROBES_BKPT_INSN 0xcc
#define UPROBES_BKPT_INSN_SIZE 1
#define MAX_UINSN_BYTES 16
#define UPROBES_XOL_SLOT_BYTES 128 /* to keep it cache aligned */

#define UPROBES_BKPT_INSN 0xcc
#define UPROBES_BKPT_INSN_SIZE 1

struct uprobe_arch_info {
u16 fixups;
u16 fixups;
#ifdef CONFIG_X86_64
unsigned long rip_rela_target_address;
unsigned long rip_rela_target_address;
#endif
};

struct uprobe;
extern int analyze_insn(struct mm_struct *mm, struct uprobe *uprobe);
extern int arch_uprobes_analyze_insn(struct mm_struct *mm, struct uprobe *uprobe);
#endif /* _ASM_UPROBES_H */
129 changes: 68 additions & 61 deletions arch/x86/kernel/uprobes.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Userspace Probes (UProbes) for x86
* User-space Probes (UProbes) for x86
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
Expand All @@ -20,7 +20,6 @@
* Srikar Dronamraju
* Jim Keniston
*/

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
Expand All @@ -42,10 +41,10 @@
#define UPROBES_FIX_RIP_CX 0x4000

/* Adaptations for mhiramat x86 decoder v14. */
#define OPCODE1(insn) ((insn)->opcode.bytes[0])
#define OPCODE2(insn) ((insn)->opcode.bytes[1])
#define OPCODE3(insn) ((insn)->opcode.bytes[2])
#define MODRM_REG(insn) X86_MODRM_REG(insn->modrm.value)
#define OPCODE1(insn) ((insn)->opcode.bytes[0])
#define OPCODE2(insn) ((insn)->opcode.bytes[1])
#define OPCODE3(insn) ((insn)->opcode.bytes[2])
#define MODRM_REG(insn) X86_MODRM_REG(insn->modrm.value)

#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
Expand All @@ -55,7 +54,7 @@
<< (row % 32))

#ifdef CONFIG_X86_64
static volatile u32 good_insns_64[256 / 32] = {
static u32 good_insns_64[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) | /* 00 */
Expand All @@ -81,7 +80,7 @@ static volatile u32 good_insns_64[256 / 32] = {

/* Good-instruction tables for 32-bit apps */

static volatile u32 good_insns_32[256 / 32] = {
static u32 good_insns_32[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) | /* 00 */
Expand All @@ -105,7 +104,7 @@ static volatile u32 good_insns_32[256 / 32] = {
};

/* Using this for both 64-bit and 32-bit apps */
static volatile u32 good_2byte_insns[256 / 32] = {
static u32 good_2byte_insns[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1) | /* 00 */
Expand All @@ -132,42 +131,47 @@ static volatile u32 good_2byte_insns[256 / 32] = {

/*
* opcodes we'll probably never support:
* 6c-6d, e4-e5, ec-ed - in
* 6e-6f, e6-e7, ee-ef - out
* cc, cd - int3, int
* cf - iret
* d6 - illegal instruction
* f1 - int1/icebp
* f4 - hlt
* fa, fb - cli, sti
* 0f - lar, lsl, syscall, clts, sysret, sysenter, sysexit, invd, wbinvd, ud2
*
* 6c-6d, e4-e5, ec-ed - in
* 6e-6f, e6-e7, ee-ef - out
* cc, cd - int3, int
* cf - iret
* d6 - illegal instruction
* f1 - int1/icebp
* f4 - hlt
* fa, fb - cli, sti
* 0f - lar, lsl, syscall, clts, sysret, sysenter, sysexit, invd, wbinvd, ud2
*
* invalid opcodes in 64-bit mode:
* 06, 0e, 16, 1e, 27, 2f, 37, 3f, 60-62, 82, c4-c5, d4-d5
*
* 63 - we support this opcode in x86_64 but not in i386.
* 06, 0e, 16, 1e, 27, 2f, 37, 3f, 60-62, 82, c4-c5, d4-d5
* 63 - we support this opcode in x86_64 but not in i386.
*
* opcodes we may need to refine support for:
* 0f - 2-byte instructions: For many of these instructions, the validity
* depends on the prefix and/or the reg field. On such instructions, we
* just consider the opcode combination valid if it corresponds to any
* valid instruction.
* 8f - Group 1 - only reg = 0 is OK
* c6-c7 - Group 11 - only reg = 0 is OK
* d9-df - fpu insns with some illegal encodings
* f2, f3 - repnz, repz prefixes. These are also the first byte for
* certain floating-point instructions, such as addsd.
* fe - Group 4 - only reg = 0 or 1 is OK
* ff - Group 5 - only reg = 0-6 is OK
*
* 0f - 2-byte instructions: For many of these instructions, the validity
* depends on the prefix and/or the reg field. On such instructions, we
* just consider the opcode combination valid if it corresponds to any
* valid instruction.
*
* 8f - Group 1 - only reg = 0 is OK
* c6-c7 - Group 11 - only reg = 0 is OK
* d9-df - fpu insns with some illegal encodings
* f2, f3 - repnz, repz prefixes. These are also the first byte for
* certain floating-point instructions, such as addsd.
*
* fe - Group 4 - only reg = 0 or 1 is OK
* ff - Group 5 - only reg = 0-6 is OK
*
* others -- Do we need to support these?
* 0f - (floating-point?) prefetch instructions
* 07, 17, 1f - pop es, pop ss, pop ds
* 26, 2e, 36, 3e - es:, cs:, ss:, ds: segment prefixes --
*
* 0f - (floating-point?) prefetch instructions
* 07, 17, 1f - pop es, pop ss, pop ds
* 26, 2e, 36, 3e - es:, cs:, ss:, ds: segment prefixes --
* but 64 and 65 (fs: and gs:) seem to be used, so we support them
* 67 - addr16 prefix
* ce - into
* f0 - lock prefix
* 67 - addr16 prefix
* ce - into
* f0 - lock prefix
*/

/*
Expand All @@ -182,11 +186,11 @@ static bool is_prefix_bad(struct insn *insn)

for (i = 0; i < insn->prefixes.nbytes; i++) {
switch (insn->prefixes.bytes[i]) {
case 0x26: /*INAT_PFX_ES */
case 0x2E: /*INAT_PFX_CS */
case 0x36: /*INAT_PFX_DS */
case 0x3E: /*INAT_PFX_SS */
case 0xF0: /*INAT_PFX_LOCK */
case 0x26: /* INAT_PFX_ES */
case 0x2E: /* INAT_PFX_CS */
case 0x36: /* INAT_PFX_DS */
case 0x3E: /* INAT_PFX_SS */
case 0xF0: /* INAT_PFX_LOCK */
return true;
}
}
Expand All @@ -201,12 +205,15 @@ static int validate_insn_32bits(struct uprobe *uprobe, struct insn *insn)
insn_get_opcode(insn);
if (is_prefix_bad(insn))
return -ENOTSUPP;

if (test_bit(OPCODE1(insn), (unsigned long *)good_insns_32))
return 0;

if (insn->opcode.nbytes == 2) {
if (test_bit(OPCODE2(insn), (unsigned long *)good_2byte_insns))
return 0;
}

return -ENOTSUPP;
}

Expand Down Expand Up @@ -282,12 +289,12 @@ static void prepare_fixups(struct uprobe *uprobe, struct insn *insn)
* disastrous.
*
* Some useful facts about rip-relative instructions:
* - There's always a modrm byte.
* - There's never a SIB byte.
* - The displacement is always 4 bytes.
*
* - There's always a modrm byte.
* - There's never a SIB byte.
* - The displacement is always 4 bytes.
*/
static void handle_riprel_insn(struct mm_struct *mm, struct uprobe *uprobe,
struct insn *insn)
static void handle_riprel_insn(struct mm_struct *mm, struct uprobe *uprobe, struct insn *insn)
{
u8 *cursor;
u8 reg;
Expand Down Expand Up @@ -342,13 +349,12 @@ static void handle_riprel_insn(struct mm_struct *mm, struct uprobe *uprobe,
}

/* Target address = address of next instruction + (signed) offset */
uprobe->arch_info.rip_rela_target_address = (long)insn->length
+ insn->displacement.value;
uprobe->arch_info.rip_rela_target_address = (long)insn->length + insn->displacement.value;

/* Displacement field is gone; slide immediate field (if any) over. */
if (insn->immediate.nbytes) {
cursor++;
memmove(cursor, cursor + insn->displacement.nbytes,
insn->immediate.nbytes);
memmove(cursor, cursor + insn->displacement.nbytes, insn->immediate.nbytes);
}
return;
}
Expand All @@ -361,43 +367,42 @@ static int validate_insn_64bits(struct uprobe *uprobe, struct insn *insn)
insn_get_opcode(insn);
if (is_prefix_bad(insn))
return -ENOTSUPP;

if (test_bit(OPCODE1(insn), (unsigned long *)good_insns_64))
return 0;

if (insn->opcode.nbytes == 2) {
if (test_bit(OPCODE2(insn), (unsigned long *)good_2byte_insns))
return 0;
}
return -ENOTSUPP;
}

static int validate_insn_bits(struct mm_struct *mm, struct uprobe *uprobe,
struct insn *insn)
static int validate_insn_bits(struct mm_struct *mm, struct uprobe *uprobe, struct insn *insn)
{
if (mm->context.ia32_compat)
return validate_insn_32bits(uprobe, insn);
return validate_insn_64bits(uprobe, insn);
}
#else
static void handle_riprel_insn(struct mm_struct *mm, struct uprobe *uprobe,
struct insn *insn)
#else /* 32-bit: */
static void handle_riprel_insn(struct mm_struct *mm, struct uprobe *uprobe, struct insn *insn)
{
return;
/* No RIP-relative addressing on 32-bit */
}

static int validate_insn_bits(struct mm_struct *mm, struct uprobe *uprobe,
struct insn *insn)
static int validate_insn_bits(struct mm_struct *mm, struct uprobe *uprobe, struct insn *insn)
{
return validate_insn_32bits(uprobe, insn);
}
#endif /* CONFIG_X86_64 */

/**
* analyze_insn - instruction analysis including validity and fixups.
* arch_uprobes_analyze_insn - instruction analysis including validity and fixups.
* @mm: the probed address space.
* @uprobe: the probepoint information.
* Return 0 on success or a -ve number on error.
*/
int analyze_insn(struct mm_struct *mm, struct uprobe *uprobe)
int arch_uprobes_analyze_insn(struct mm_struct *mm, struct uprobe *uprobe)
{
int ret;
struct insn insn;
Expand All @@ -406,7 +411,9 @@ int analyze_insn(struct mm_struct *mm, struct uprobe *uprobe)
ret = validate_insn_bits(mm, uprobe, &insn);
if (ret != 0)
return ret;

handle_riprel_insn(mm, uprobe, &insn);
prepare_fixups(uprobe, &insn);

return 0;
}
28 changes: 13 additions & 15 deletions include/linux/uprobes.h
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
#ifndef _LINUX_UPROBES_H
#define _LINUX_UPROBES_H
/*
* Userspace Probes (UProbes)
* User-space Probes (UProbes)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
Expand Down Expand Up @@ -40,8 +40,10 @@ struct uprobe_arch_info {};
#define uprobe_opcode_sz sizeof(uprobe_opcode_t)

/* flags that denote/change uprobes behaviour */

/* Have a copy of original instruction */
#define UPROBES_COPY_INSN 0x1

/* Dont run handlers when first register/ last unregister in progress*/
#define UPROBES_RUN_HANDLER 0x2

Expand Down Expand Up @@ -70,27 +72,23 @@ struct uprobe {
};

#ifdef CONFIG_UPROBES
extern int __weak set_bkpt(struct mm_struct *mm, struct uprobe *uprobe,
unsigned long vaddr);
extern int __weak set_orig_insn(struct mm_struct *mm, struct uprobe *uprobe,
unsigned long vaddr, bool verify);
extern int __weak set_bkpt(struct mm_struct *mm, struct uprobe *uprobe, unsigned long vaddr);
extern int __weak set_orig_insn(struct mm_struct *mm, struct uprobe *uprobe, unsigned long vaddr, bool verify);
extern bool __weak is_bkpt_insn(uprobe_opcode_t *insn);
extern int register_uprobe(struct inode *inode, loff_t offset,
struct uprobe_consumer *consumer);
extern void unregister_uprobe(struct inode *inode, loff_t offset,
struct uprobe_consumer *consumer);
extern int mmap_uprobe(struct vm_area_struct *vma);
extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer);
extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer);
extern int uprobe_mmap(struct vm_area_struct *vma);
#else /* CONFIG_UPROBES is not defined */
static inline int register_uprobe(struct inode *inode, loff_t offset,
struct uprobe_consumer *consumer)
static inline int
uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer)
{
return -ENOSYS;
}
static inline void unregister_uprobe(struct inode *inode, loff_t offset,
struct uprobe_consumer *consumer)
static inline void
uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer)
{
}
static inline int mmap_uprobe(struct vm_area_struct *vma)
static inline int uprobe_mmap(struct vm_area_struct *vma)
{
return 0;
}
Expand Down
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