https://github.com/torvalds/linux
Tip revision: c3f38fa61af77b49866b006939479069cd451173 authored by Linus Torvalds on 02 June 2024, 22:44:56 UTC
Linux 6.10-rc2
Linux 6.10-rc2
Tip revision: c3f38fa
core.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Kernel Probes (KProbes)
*
* Copyright (C) IBM Corporation, 2002, 2004
*
* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
* Probes initial implementation ( includes contributions from
* Rusty Russell).
* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
* interface to access function arguments.
* 2004-Oct Jim Keniston <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
* <prasanna@in.ibm.com> adapted for x86_64 from i386.
* 2005-Mar Roland McGrath <roland@redhat.com>
* Fixed to handle %rip-relative addressing mode correctly.
* 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
* <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
* <prasanna@in.ibm.com> added function-return probes.
* 2005-May Rusty Lynch <rusty.lynch@intel.com>
* Added function return probes functionality
* 2006-Feb Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> added
* kprobe-booster and kretprobe-booster for i386.
* 2007-Dec Masami Hiramatsu <mhiramat@redhat.com> added kprobe-booster
* and kretprobe-booster for x86-64
* 2007-Dec Masami Hiramatsu <mhiramat@redhat.com>, Arjan van de Ven
* <arjan@infradead.org> and Jim Keniston <jkenisto@us.ibm.com>
* unified x86 kprobes code.
*/
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/hardirq.h>
#include <linux/preempt.h>
#include <linux/sched/debug.h>
#include <linux/perf_event.h>
#include <linux/extable.h>
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
#include <linux/kgdb.h>
#include <linux/ftrace.h>
#include <linux/kasan.h>
#include <linux/objtool.h>
#include <linux/vmalloc.h>
#include <linux/pgtable.h>
#include <linux/set_memory.h>
#include <linux/cfi.h>
#include <linux/execmem.h>
#include <asm/text-patching.h>
#include <asm/cacheflush.h>
#include <asm/desc.h>
#include <linux/uaccess.h>
#include <asm/alternative.h>
#include <asm/insn.h>
#include <asm/debugreg.h>
#include <asm/ibt.h>
#include "common.h"
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
#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) | \
(b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
(b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
(bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
<< (row % 32))
/*
* Undefined/reserved opcodes, conditional jump, Opcode Extension
* Groups, and some special opcodes can not boost.
* This is non-const and volatile to keep gcc from statically
* optimizing it out, as variable_test_bit makes gcc think only
* *(unsigned long*) is used.
*/
static volatile u32 twobyte_is_boostable[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
/* ----------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
#undef W
struct kretprobe_blackpoint kretprobe_blacklist[] = {
{"__switch_to", }, /* This function switches only current task, but
doesn't switch kernel stack.*/
{NULL, NULL} /* Terminator */
};
const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
static nokprobe_inline void
__synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
{
struct __arch_relative_insn {
u8 op;
s32 raddr;
} __packed *insn;
insn = (struct __arch_relative_insn *)dest;
insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
insn->op = op;
}
/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
void synthesize_reljump(void *dest, void *from, void *to)
{
__synthesize_relative_insn(dest, from, to, JMP32_INSN_OPCODE);
}
NOKPROBE_SYMBOL(synthesize_reljump);
/* Insert a call instruction at address 'from', which calls address 'to'.*/
void synthesize_relcall(void *dest, void *from, void *to)
{
__synthesize_relative_insn(dest, from, to, CALL_INSN_OPCODE);
}
NOKPROBE_SYMBOL(synthesize_relcall);
/*
* Returns non-zero if INSN is boostable.
* RIP relative instructions are adjusted at copying time in 64 bits mode
*/
bool can_boost(struct insn *insn, void *addr)
{
kprobe_opcode_t opcode;
insn_byte_t prefix;
int i;
if (search_exception_tables((unsigned long)addr))
return false; /* Page fault may occur on this address. */
/* 2nd-byte opcode */
if (insn->opcode.nbytes == 2)
return test_bit(insn->opcode.bytes[1],
(unsigned long *)twobyte_is_boostable);
if (insn->opcode.nbytes != 1)
return false;
for_each_insn_prefix(insn, i, prefix) {
insn_attr_t attr;
attr = inat_get_opcode_attribute(prefix);
/* Can't boost Address-size override prefix and CS override prefix */
if (prefix == 0x2e || inat_is_address_size_prefix(attr))
return false;
}
opcode = insn->opcode.bytes[0];
switch (opcode) {
case 0x62: /* bound */
case 0x70 ... 0x7f: /* Conditional jumps */
case 0x9a: /* Call far */
case 0xcc ... 0xce: /* software exceptions */
case 0xd6: /* (UD) */
case 0xd8 ... 0xdf: /* ESC */
case 0xe0 ... 0xe3: /* LOOP*, JCXZ */
case 0xe8 ... 0xe9: /* near Call, JMP */
case 0xeb: /* Short JMP */
case 0xf0 ... 0xf4: /* LOCK/REP, HLT */
/* ... are not boostable */
return false;
case 0xc0 ... 0xc1: /* Grp2 */
case 0xd0 ... 0xd3: /* Grp2 */
/*
* AMD uses nnn == 110 as SHL/SAL, but Intel makes it reserved.
*/
return X86_MODRM_REG(insn->modrm.bytes[0]) != 0b110;
case 0xf6 ... 0xf7: /* Grp3 */
/* AMD uses nnn == 001 as TEST, but Intel makes it reserved. */
return X86_MODRM_REG(insn->modrm.bytes[0]) != 0b001;
case 0xfe: /* Grp4 */
/* Only INC and DEC are boostable */
return X86_MODRM_REG(insn->modrm.bytes[0]) == 0b000 ||
X86_MODRM_REG(insn->modrm.bytes[0]) == 0b001;
case 0xff: /* Grp5 */
/* Only INC, DEC, and indirect JMP are boostable */
return X86_MODRM_REG(insn->modrm.bytes[0]) == 0b000 ||
X86_MODRM_REG(insn->modrm.bytes[0]) == 0b001 ||
X86_MODRM_REG(insn->modrm.bytes[0]) == 0b100;
default:
return true;
}
}
static unsigned long
__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
{
struct kprobe *kp;
bool faddr;
kp = get_kprobe((void *)addr);
faddr = ftrace_location(addr) == addr;
/*
* Use the current code if it is not modified by Kprobe
* and it cannot be modified by ftrace.
*/
if (!kp && !faddr)
return addr;
/*
* Basically, kp->ainsn.insn has an original instruction.
* However, RIP-relative instruction can not do single-stepping
* at different place, __copy_instruction() tweaks the displacement of
* that instruction. In that case, we can't recover the instruction
* from the kp->ainsn.insn.
*
* On the other hand, in case on normal Kprobe, kp->opcode has a copy
* of the first byte of the probed instruction, which is overwritten
* by int3. And the instruction at kp->addr is not modified by kprobes
* except for the first byte, we can recover the original instruction
* from it and kp->opcode.
*
* In case of Kprobes using ftrace, we do not have a copy of
* the original instruction. In fact, the ftrace location might
* be modified at anytime and even could be in an inconsistent state.
* Fortunately, we know that the original code is the ideal 5-byte
* long NOP.
*/
if (copy_from_kernel_nofault(buf, (void *)addr,
MAX_INSN_SIZE * sizeof(kprobe_opcode_t)))
return 0UL;
if (faddr)
memcpy(buf, x86_nops[5], 5);
else
buf[0] = kp->opcode;
return (unsigned long)buf;
}
/*
* Recover the probed instruction at addr for further analysis.
* Caller must lock kprobes by kprobe_mutex, or disable preemption
* for preventing to release referencing kprobes.
* Returns zero if the instruction can not get recovered (or access failed).
*/
unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
{
unsigned long __addr;
__addr = __recover_optprobed_insn(buf, addr);
if (__addr != addr)
return __addr;
return __recover_probed_insn(buf, addr);
}
/* Check if insn is INT or UD */
static inline bool is_exception_insn(struct insn *insn)
{
/* UD uses 0f escape */
if (insn->opcode.bytes[0] == 0x0f) {
/* UD0 / UD1 / UD2 */
return insn->opcode.bytes[1] == 0xff ||
insn->opcode.bytes[1] == 0xb9 ||
insn->opcode.bytes[1] == 0x0b;
}
/* INT3 / INT n / INTO / INT1 */
return insn->opcode.bytes[0] == 0xcc ||
insn->opcode.bytes[0] == 0xcd ||
insn->opcode.bytes[0] == 0xce ||
insn->opcode.bytes[0] == 0xf1;
}
/*
* Check if paddr is at an instruction boundary and that instruction can
* be probed
*/
static bool can_probe(unsigned long paddr)
{
unsigned long addr, __addr, offset = 0;
struct insn insn;
kprobe_opcode_t buf[MAX_INSN_SIZE];
if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
return false;
/* Decode instructions */
addr = paddr - offset;
while (addr < paddr) {
/*
* Check if the instruction has been modified by another
* kprobe, in which case we replace the breakpoint by the
* original instruction in our buffer.
* Also, jump optimization will change the breakpoint to
* relative-jump. Since the relative-jump itself is
* normally used, we just go through if there is no kprobe.
*/
__addr = recover_probed_instruction(buf, addr);
if (!__addr)
return false;
if (insn_decode_kernel(&insn, (void *)__addr) < 0)
return false;
#ifdef CONFIG_KGDB
/*
* If there is a dynamically installed kgdb sw breakpoint,
* this function should not be probed.
*/
if (insn.opcode.bytes[0] == INT3_INSN_OPCODE &&
kgdb_has_hit_break(addr))
return false;
#endif
addr += insn.length;
}
/* Check if paddr is at an instruction boundary */
if (addr != paddr)
return false;
__addr = recover_probed_instruction(buf, addr);
if (!__addr)
return false;
if (insn_decode_kernel(&insn, (void *)__addr) < 0)
return false;
/* INT and UD are special and should not be kprobed */
if (is_exception_insn(&insn))
return false;
if (IS_ENABLED(CONFIG_CFI_CLANG)) {
/*
* The compiler generates the following instruction sequence
* for indirect call checks and cfi.c decodes this;
*
* movl -<id>, %r10d ; 6 bytes
* addl -4(%reg), %r10d ; 4 bytes
* je .Ltmp1 ; 2 bytes
* ud2 ; <- regs->ip
* .Ltmp1:
*
* Also, these movl and addl are used for showing expected
* type. So those must not be touched.
*/
if (insn.opcode.value == 0xBA)
offset = 12;
else if (insn.opcode.value == 0x3)
offset = 6;
else
goto out;
/* This movl/addl is used for decoding CFI. */
if (is_cfi_trap(addr + offset))
return false;
}
out:
return true;
}
/* If x86 supports IBT (ENDBR) it must be skipped. */
kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
bool *on_func_entry)
{
u32 insn;
/*
* Since 'addr' is not guaranteed to be safe to access, use
* copy_from_kernel_nofault() to read the instruction:
*/
if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(u32)))
return NULL;
if (is_endbr(insn)) {
*on_func_entry = !offset || offset == 4;
if (*on_func_entry)
offset = 4;
} else {
*on_func_entry = !offset;
}
return (kprobe_opcode_t *)(addr + offset);
}
/*
* Copy an instruction with recovering modified instruction by kprobes
* and adjust the displacement if the instruction uses the %rip-relative
* addressing mode. Note that since @real will be the final place of copied
* instruction, displacement must be adjust by @real, not @dest.
* This returns the length of copied instruction, or 0 if it has an error.
*/
int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
{
kprobe_opcode_t buf[MAX_INSN_SIZE];
unsigned long recovered_insn = recover_probed_instruction(buf, (unsigned long)src);
int ret;
if (!recovered_insn || !insn)
return 0;
/* This can access kernel text if given address is not recovered */
if (copy_from_kernel_nofault(dest, (void *)recovered_insn,
MAX_INSN_SIZE))
return 0;
ret = insn_decode_kernel(insn, dest);
if (ret < 0)
return 0;
/* We can not probe force emulate prefixed instruction */
if (insn_has_emulate_prefix(insn))
return 0;
/* Another subsystem puts a breakpoint, failed to recover */
if (insn->opcode.bytes[0] == INT3_INSN_OPCODE)
return 0;
/* We should not singlestep on the exception masking instructions */
if (insn_masking_exception(insn))
return 0;
#ifdef CONFIG_X86_64
/* Only x86_64 has RIP relative instructions */
if (insn_rip_relative(insn)) {
s64 newdisp;
u8 *disp;
/*
* The copied instruction uses the %rip-relative addressing
* mode. Adjust the displacement for the difference between
* the original location of this instruction and the location
* of the copy that will actually be run. The tricky bit here
* is making sure that the sign extension happens correctly in
* this calculation, since we need a signed 32-bit result to
* be sign-extended to 64 bits when it's added to the %rip
* value and yield the same 64-bit result that the sign-
* extension of the original signed 32-bit displacement would
* have given.
*/
newdisp = (u8 *) src + (s64) insn->displacement.value
- (u8 *) real;
if ((s64) (s32) newdisp != newdisp) {
pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
return 0;
}
disp = (u8 *) dest + insn_offset_displacement(insn);
*(s32 *) disp = (s32) newdisp;
}
#endif
return insn->length;
}
/* Prepare reljump or int3 right after instruction */
static int prepare_singlestep(kprobe_opcode_t *buf, struct kprobe *p,
struct insn *insn)
{
int len = insn->length;
if (!IS_ENABLED(CONFIG_PREEMPTION) &&
!p->post_handler && can_boost(insn, p->addr) &&
MAX_INSN_SIZE - len >= JMP32_INSN_SIZE) {
/*
* These instructions can be executed directly if it
* jumps back to correct address.
*/
synthesize_reljump(buf + len, p->ainsn.insn + len,
p->addr + insn->length);
len += JMP32_INSN_SIZE;
p->ainsn.boostable = 1;
} else {
/* Otherwise, put an int3 for trapping singlestep */
if (MAX_INSN_SIZE - len < INT3_INSN_SIZE)
return -ENOSPC;
buf[len] = INT3_INSN_OPCODE;
len += INT3_INSN_SIZE;
}
return len;
}
/* Make page to RO mode when allocate it */
void *alloc_insn_page(void)
{
void *page;
page = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE);
if (!page)
return NULL;
/*
* TODO: Once additional kernel code protection mechanisms are set, ensure
* that the page was not maliciously altered and it is still zeroed.
*/
set_memory_rox((unsigned long)page, 1);
return page;
}
/* Kprobe x86 instruction emulation - only regs->ip or IF flag modifiers */
static void kprobe_emulate_ifmodifiers(struct kprobe *p, struct pt_regs *regs)
{
switch (p->ainsn.opcode) {
case 0xfa: /* cli */
regs->flags &= ~(X86_EFLAGS_IF);
break;
case 0xfb: /* sti */
regs->flags |= X86_EFLAGS_IF;
break;
case 0x9c: /* pushf */
int3_emulate_push(regs, regs->flags);
break;
case 0x9d: /* popf */
regs->flags = int3_emulate_pop(regs);
break;
}
regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
}
NOKPROBE_SYMBOL(kprobe_emulate_ifmodifiers);
static void kprobe_emulate_ret(struct kprobe *p, struct pt_regs *regs)
{
int3_emulate_ret(regs);
}
NOKPROBE_SYMBOL(kprobe_emulate_ret);
static void kprobe_emulate_call(struct kprobe *p, struct pt_regs *regs)
{
unsigned long func = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
func += p->ainsn.rel32;
int3_emulate_call(regs, func);
}
NOKPROBE_SYMBOL(kprobe_emulate_call);
static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs)
{
unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
ip += p->ainsn.rel32;
int3_emulate_jmp(regs, ip);
}
NOKPROBE_SYMBOL(kprobe_emulate_jmp);
static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs)
{
unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
int3_emulate_jcc(regs, p->ainsn.jcc.type, ip, p->ainsn.rel32);
}
NOKPROBE_SYMBOL(kprobe_emulate_jcc);
static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs)
{
unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
bool match;
if (p->ainsn.loop.type != 3) { /* LOOP* */
if (p->ainsn.loop.asize == 32)
match = ((*(u32 *)®s->cx)--) != 0;
#ifdef CONFIG_X86_64
else if (p->ainsn.loop.asize == 64)
match = ((*(u64 *)®s->cx)--) != 0;
#endif
else
match = ((*(u16 *)®s->cx)--) != 0;
} else { /* JCXZ */
if (p->ainsn.loop.asize == 32)
match = *(u32 *)(®s->cx) == 0;
#ifdef CONFIG_X86_64
else if (p->ainsn.loop.asize == 64)
match = *(u64 *)(®s->cx) == 0;
#endif
else
match = *(u16 *)(®s->cx) == 0;
}
if (p->ainsn.loop.type == 0) /* LOOPNE */
match = match && !(regs->flags & X86_EFLAGS_ZF);
else if (p->ainsn.loop.type == 1) /* LOOPE */
match = match && (regs->flags & X86_EFLAGS_ZF);
if (match)
ip += p->ainsn.rel32;
int3_emulate_jmp(regs, ip);
}
NOKPROBE_SYMBOL(kprobe_emulate_loop);
static const int addrmode_regoffs[] = {
offsetof(struct pt_regs, ax),
offsetof(struct pt_regs, cx),
offsetof(struct pt_regs, dx),
offsetof(struct pt_regs, bx),
offsetof(struct pt_regs, sp),
offsetof(struct pt_regs, bp),
offsetof(struct pt_regs, si),
offsetof(struct pt_regs, di),
#ifdef CONFIG_X86_64
offsetof(struct pt_regs, r8),
offsetof(struct pt_regs, r9),
offsetof(struct pt_regs, r10),
offsetof(struct pt_regs, r11),
offsetof(struct pt_regs, r12),
offsetof(struct pt_regs, r13),
offsetof(struct pt_regs, r14),
offsetof(struct pt_regs, r15),
#endif
};
static void kprobe_emulate_call_indirect(struct kprobe *p, struct pt_regs *regs)
{
unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + p->ainsn.size);
int3_emulate_jmp(regs, regs_get_register(regs, offs));
}
NOKPROBE_SYMBOL(kprobe_emulate_call_indirect);
static void kprobe_emulate_jmp_indirect(struct kprobe *p, struct pt_regs *regs)
{
unsigned long offs = addrmode_regoffs[p->ainsn.indirect.reg];
int3_emulate_jmp(regs, regs_get_register(regs, offs));
}
NOKPROBE_SYMBOL(kprobe_emulate_jmp_indirect);
static int prepare_emulation(struct kprobe *p, struct insn *insn)
{
insn_byte_t opcode = insn->opcode.bytes[0];
switch (opcode) {
case 0xfa: /* cli */
case 0xfb: /* sti */
case 0x9c: /* pushfl */
case 0x9d: /* popf/popfd */
/*
* IF modifiers must be emulated since it will enable interrupt while
* int3 single stepping.
*/
p->ainsn.emulate_op = kprobe_emulate_ifmodifiers;
p->ainsn.opcode = opcode;
break;
case 0xc2: /* ret/lret */
case 0xc3:
case 0xca:
case 0xcb:
p->ainsn.emulate_op = kprobe_emulate_ret;
break;
case 0x9a: /* far call absolute -- segment is not supported */
case 0xea: /* far jmp absolute -- segment is not supported */
case 0xcc: /* int3 */
case 0xcf: /* iret -- in-kernel IRET is not supported */
return -EOPNOTSUPP;
break;
case 0xe8: /* near call relative */
p->ainsn.emulate_op = kprobe_emulate_call;
if (insn->immediate.nbytes == 2)
p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
else
p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
break;
case 0xeb: /* short jump relative */
case 0xe9: /* near jump relative */
p->ainsn.emulate_op = kprobe_emulate_jmp;
if (insn->immediate.nbytes == 1)
p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
else if (insn->immediate.nbytes == 2)
p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
else
p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
break;
case 0x70 ... 0x7f:
/* 1 byte conditional jump */
p->ainsn.emulate_op = kprobe_emulate_jcc;
p->ainsn.jcc.type = opcode & 0xf;
p->ainsn.rel32 = insn->immediate.value;
break;
case 0x0f:
opcode = insn->opcode.bytes[1];
if ((opcode & 0xf0) == 0x80) {
/* 2 bytes Conditional Jump */
p->ainsn.emulate_op = kprobe_emulate_jcc;
p->ainsn.jcc.type = opcode & 0xf;
if (insn->immediate.nbytes == 2)
p->ainsn.rel32 = *(s16 *)&insn->immediate.value;
else
p->ainsn.rel32 = *(s32 *)&insn->immediate.value;
} else if (opcode == 0x01 &&
X86_MODRM_REG(insn->modrm.bytes[0]) == 0 &&
X86_MODRM_MOD(insn->modrm.bytes[0]) == 3) {
/* VM extensions - not supported */
return -EOPNOTSUPP;
}
break;
case 0xe0: /* Loop NZ */
case 0xe1: /* Loop */
case 0xe2: /* Loop */
case 0xe3: /* J*CXZ */
p->ainsn.emulate_op = kprobe_emulate_loop;
p->ainsn.loop.type = opcode & 0x3;
p->ainsn.loop.asize = insn->addr_bytes * 8;
p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
break;
case 0xff:
/*
* Since the 0xff is an extended group opcode, the instruction
* is determined by the MOD/RM byte.
*/
opcode = insn->modrm.bytes[0];
switch (X86_MODRM_REG(opcode)) {
case 0b010: /* FF /2, call near, absolute indirect */
p->ainsn.emulate_op = kprobe_emulate_call_indirect;
break;
case 0b100: /* FF /4, jmp near, absolute indirect */
p->ainsn.emulate_op = kprobe_emulate_jmp_indirect;
break;
case 0b011: /* FF /3, call far, absolute indirect */
case 0b101: /* FF /5, jmp far, absolute indirect */
return -EOPNOTSUPP;
}
if (!p->ainsn.emulate_op)
break;
if (insn->addr_bytes != sizeof(unsigned long))
return -EOPNOTSUPP; /* Don't support different size */
if (X86_MODRM_MOD(opcode) != 3)
return -EOPNOTSUPP; /* TODO: support memory addressing */
p->ainsn.indirect.reg = X86_MODRM_RM(opcode);
#ifdef CONFIG_X86_64
if (X86_REX_B(insn->rex_prefix.value))
p->ainsn.indirect.reg += 8;
#endif
break;
default:
break;
}
p->ainsn.size = insn->length;
return 0;
}
static int arch_copy_kprobe(struct kprobe *p)
{
struct insn insn;
kprobe_opcode_t buf[MAX_INSN_SIZE];
int ret, len;
/* Copy an instruction with recovering if other optprobe modifies it.*/
len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
if (!len)
return -EINVAL;
/* Analyze the opcode and setup emulate functions */
ret = prepare_emulation(p, &insn);
if (ret < 0)
return ret;
/* Add int3 for single-step or booster jmp */
len = prepare_singlestep(buf, p, &insn);
if (len < 0)
return len;
/* Also, displacement change doesn't affect the first byte */
p->opcode = buf[0];
p->ainsn.tp_len = len;
perf_event_text_poke(p->ainsn.insn, NULL, 0, buf, len);
/* OK, write back the instruction(s) into ROX insn buffer */
text_poke(p->ainsn.insn, buf, len);
return 0;
}
int arch_prepare_kprobe(struct kprobe *p)
{
int ret;
if (alternatives_text_reserved(p->addr, p->addr))
return -EINVAL;
if (!can_probe((unsigned long)p->addr))
return -EILSEQ;
memset(&p->ainsn, 0, sizeof(p->ainsn));
/* insn: must be on special executable page on x86. */
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn)
return -ENOMEM;
ret = arch_copy_kprobe(p);
if (ret) {
free_insn_slot(p->ainsn.insn, 0);
p->ainsn.insn = NULL;
}
return ret;
}
void arch_arm_kprobe(struct kprobe *p)
{
u8 int3 = INT3_INSN_OPCODE;
text_poke(p->addr, &int3, 1);
text_poke_sync();
perf_event_text_poke(p->addr, &p->opcode, 1, &int3, 1);
}
void arch_disarm_kprobe(struct kprobe *p)
{
u8 int3 = INT3_INSN_OPCODE;
perf_event_text_poke(p->addr, &int3, 1, &p->opcode, 1);
text_poke(p->addr, &p->opcode, 1);
text_poke_sync();
}
void arch_remove_kprobe(struct kprobe *p)
{
if (p->ainsn.insn) {
/* Record the perf event before freeing the slot */
perf_event_text_poke(p->ainsn.insn, p->ainsn.insn,
p->ainsn.tp_len, NULL, 0);
free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
p->ainsn.insn = NULL;
}
}
static nokprobe_inline void
save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
kcb->prev_kprobe.kp = kprobe_running();
kcb->prev_kprobe.status = kcb->kprobe_status;
kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
}
static nokprobe_inline void
restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
kcb->kprobe_status = kcb->prev_kprobe.status;
kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
}
static nokprobe_inline void
set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
__this_cpu_write(current_kprobe, p);
kcb->kprobe_saved_flags = kcb->kprobe_old_flags
= (regs->flags & X86_EFLAGS_IF);
}
static void kprobe_post_process(struct kprobe *cur, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
/* Restore back the original saved kprobes variables and continue. */
if (kcb->kprobe_status == KPROBE_REENTER) {
/* This will restore both kcb and current_kprobe */
restore_previous_kprobe(kcb);
} else {
/*
* Always update the kcb status because
* reset_curent_kprobe() doesn't update kcb.
*/
kcb->kprobe_status = KPROBE_HIT_SSDONE;
if (cur->post_handler)
cur->post_handler(cur, regs, 0);
reset_current_kprobe();
}
}
NOKPROBE_SYMBOL(kprobe_post_process);
static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb, int reenter)
{
if (setup_detour_execution(p, regs, reenter))
return;
#if !defined(CONFIG_PREEMPTION)
if (p->ainsn.boostable) {
/* Boost up -- we can execute copied instructions directly */
if (!reenter)
reset_current_kprobe();
/*
* Reentering boosted probe doesn't reset current_kprobe,
* nor set current_kprobe, because it doesn't use single
* stepping.
*/
regs->ip = (unsigned long)p->ainsn.insn;
return;
}
#endif
if (reenter) {
save_previous_kprobe(kcb);
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_REENTER;
} else
kcb->kprobe_status = KPROBE_HIT_SS;
if (p->ainsn.emulate_op) {
p->ainsn.emulate_op(p, regs);
kprobe_post_process(p, regs, kcb);
return;
}
/* Disable interrupt, and set ip register on trampoline */
regs->flags &= ~X86_EFLAGS_IF;
regs->ip = (unsigned long)p->ainsn.insn;
}
NOKPROBE_SYMBOL(setup_singlestep);
/*
* Called after single-stepping. p->addr is the address of the
* instruction whose first byte has been replaced by the "int3"
* instruction. To avoid the SMP problems that can occur when we
* temporarily put back the original opcode to single-step, we
* single-stepped a copy of the instruction. The address of this
* copy is p->ainsn.insn. We also doesn't use trap, but "int3" again
* right after the copied instruction.
* Different from the trap single-step, "int3" single-step can not
* handle the instruction which changes the ip register, e.g. jmp,
* call, conditional jmp, and the instructions which changes the IF
* flags because interrupt must be disabled around the single-stepping.
* Such instructions are software emulated, but others are single-stepped
* using "int3".
*
* When the 2nd "int3" handled, the regs->ip and regs->flags needs to
* be adjusted, so that we can resume execution on correct code.
*/
static void resume_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
unsigned long copy_ip = (unsigned long)p->ainsn.insn;
unsigned long orig_ip = (unsigned long)p->addr;
/* Restore saved interrupt flag and ip register */
regs->flags |= kcb->kprobe_saved_flags;
/* Note that regs->ip is executed int3 so must be a step back */
regs->ip += (orig_ip - copy_ip) - INT3_INSN_SIZE;
}
NOKPROBE_SYMBOL(resume_singlestep);
/*
* We have reentered the kprobe_handler(), since another probe was hit while
* within the handler. We save the original kprobes variables and just single
* step on the instruction of the new probe without calling any user handlers.
*/
static int reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
switch (kcb->kprobe_status) {
case KPROBE_HIT_SSDONE:
case KPROBE_HIT_ACTIVE:
case KPROBE_HIT_SS:
kprobes_inc_nmissed_count(p);
setup_singlestep(p, regs, kcb, 1);
break;
case KPROBE_REENTER:
/* A probe has been hit in the codepath leading up to, or just
* after, single-stepping of a probed instruction. This entire
* codepath should strictly reside in .kprobes.text section.
* Raise a BUG or we'll continue in an endless reentering loop
* and eventually a stack overflow.
*/
pr_err("Unrecoverable kprobe detected.\n");
dump_kprobe(p);
BUG();
default:
/* impossible cases */
WARN_ON(1);
return 0;
}
return 1;
}
NOKPROBE_SYMBOL(reenter_kprobe);
static nokprobe_inline int kprobe_is_ss(struct kprobe_ctlblk *kcb)
{
return (kcb->kprobe_status == KPROBE_HIT_SS ||
kcb->kprobe_status == KPROBE_REENTER);
}
/*
* Interrupts are disabled on entry as trap3 is an interrupt gate and they
* remain disabled throughout this function.
*/
int kprobe_int3_handler(struct pt_regs *regs)
{
kprobe_opcode_t *addr;
struct kprobe *p;
struct kprobe_ctlblk *kcb;
if (user_mode(regs))
return 0;
addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
/*
* We don't want to be preempted for the entire duration of kprobe
* processing. Since int3 and debug trap disables irqs and we clear
* IF while singlestepping, it must be no preemptible.
*/
kcb = get_kprobe_ctlblk();
p = get_kprobe(addr);
if (p) {
if (kprobe_running()) {
if (reenter_kprobe(p, regs, kcb))
return 1;
} else {
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
/*
* If we have no pre-handler or it returned 0, we
* continue with normal processing. If we have a
* pre-handler and it returned non-zero, that means
* user handler setup registers to exit to another
* instruction, we must skip the single stepping.
*/
if (!p->pre_handler || !p->pre_handler(p, regs))
setup_singlestep(p, regs, kcb, 0);
else
reset_current_kprobe();
return 1;
}
} else if (kprobe_is_ss(kcb)) {
p = kprobe_running();
if ((unsigned long)p->ainsn.insn < regs->ip &&
(unsigned long)p->ainsn.insn + MAX_INSN_SIZE > regs->ip) {
/* Most provably this is the second int3 for singlestep */
resume_singlestep(p, regs, kcb);
kprobe_post_process(p, regs, kcb);
return 1;
}
} /* else: not a kprobe fault; let the kernel handle it */
return 0;
}
NOKPROBE_SYMBOL(kprobe_int3_handler);
int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
/* This must happen on single-stepping */
WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
kcb->kprobe_status != KPROBE_REENTER);
/*
* We are here because the instruction being single
* stepped caused a page fault. We reset the current
* kprobe and the ip points back to the probe address
* and allow the page fault handler to continue as a
* normal page fault.
*/
regs->ip = (unsigned long)cur->addr;
/*
* If the IF flag was set before the kprobe hit,
* don't touch it:
*/
regs->flags |= kcb->kprobe_old_flags;
if (kcb->kprobe_status == KPROBE_REENTER)
restore_previous_kprobe(kcb);
else
reset_current_kprobe();
}
return 0;
}
NOKPROBE_SYMBOL(kprobe_fault_handler);
int __init arch_populate_kprobe_blacklist(void)
{
return kprobe_add_area_blacklist((unsigned long)__entry_text_start,
(unsigned long)__entry_text_end);
}
int __init arch_init_kprobes(void)
{
return 0;
}
int arch_trampoline_kprobe(struct kprobe *p)
{
return 0;
}