// SPDX-License-Identifier: GPL-2.0-or-later
/*
* User-space Probes (UProbes) for x86
*
* Copyright (C) IBM Corporation, 2008-2011
* Authors:
* Srikar Dronamraju
* Jim Keniston
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/uprobes.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>
#include <asm/processor.h>
#include <asm/insn.h>
#include <asm/mmu_context.h>
/* Post-execution fixups. */
/* Adjust IP back to vicinity of actual insn */
#define UPROBE_FIX_IP 0x01
/* Adjust the return address of a call insn */
#define UPROBE_FIX_CALL 0x02
/* Instruction will modify TF, don't change it */
#define UPROBE_FIX_SETF 0x04
#define UPROBE_FIX_RIP_SI 0x08
#define UPROBE_FIX_RIP_DI 0x10
#define UPROBE_FIX_RIP_BX 0x20
#define UPROBE_FIX_RIP_MASK \
(UPROBE_FIX_RIP_SI | UPROBE_FIX_RIP_DI | UPROBE_FIX_RIP_BX)
#define UPROBE_TRAP_NR UINT_MAX
/* 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 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))
/*
* Good-instruction tables for 32-bit apps. This is non-const and volatile
* to keep gcc from statically optimizing it out, as variable_test_bit makes
* some versions of gcc to think only *(unsigned long*) is used.
*
* Opcodes we'll probably never support:
* 6c-6f - ins,outs. SEGVs if used in userspace
* e4-e7 - in,out imm. SEGVs if used in userspace
* ec-ef - in,out acc. SEGVs if used in userspace
* cc - int3. SIGTRAP if used in userspace
* ce - into. Not used in userspace - no kernel support to make it useful. SEGVs
* (why we support bound (62) then? it's similar, and similarly unused...)
* f1 - int1. SIGTRAP if used in userspace
* f4 - hlt. SEGVs if used in userspace
* fa - cli. SEGVs if used in userspace
* fb - sti. SEGVs if used in userspace
*
* Opcodes which need some work to be supported:
* 07,17,1f - pop es/ss/ds
* Normally not used in userspace, but would execute if used.
* Can cause GP or stack exception if tries to load wrong segment descriptor.
* We hesitate to run them under single step since kernel's handling
* of userspace single-stepping (TF flag) is fragile.
* We can easily refuse to support push es/cs/ss/ds (06/0e/16/1e)
* on the same grounds that they are never used.
* cd - int N.
* Used by userspace for "int 80" syscall entry. (Other "int N"
* cause GP -> SEGV since their IDT gates don't allow calls from CPL 3).
* Not supported since kernel's handling of userspace single-stepping
* (TF flag) is fragile.
* cf - iret. Normally not used in userspace. Doesn't SEGV unless arguments are bad
*/
#if defined([31mCONFIG_X86_32[0m) || defined([31mCONFIG_IA32_EMULATION[0m)
static volatile 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, 1) | /* 00 */
W(0x10, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 10 */
W(0x20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */
W(0x30, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* e0 */
W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */
/* ---------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
#else
#define good_insns_32 NULL
#endif
/* Good-instruction tables for 64-bit apps.
*
* Genuinely invalid opcodes:
* 06,07 - formerly push/pop es
* 0e - formerly push cs
* 16,17 - formerly push/pop ss
* 1e,1f - formerly push/pop ds
* 27,2f,37,3f - formerly daa/das/aaa/aas
* 60,61 - formerly pusha/popa
* 62 - formerly bound. EVEX prefix for AVX512 (not yet supported)
* 82 - formerly redundant encoding of Group1
* 9a - formerly call seg:ofs
* ce - formerly into
* d4,d5 - formerly aam/aad
* d6 - formerly undocumented salc
* ea - formerly jmp seg:ofs
*
* Opcodes we'll probably never support:
* 6c-6f - ins,outs. SEGVs if used in userspace
* e4-e7 - in,out imm. SEGVs if used in userspace
* ec-ef - in,out acc. SEGVs if used in userspace
* cc - int3. SIGTRAP if used in userspace
* f1 - int1. SIGTRAP if used in userspace
* f4 - hlt. SEGVs if used in userspace
* fa - cli. SEGVs if used in userspace
* fb - sti. SEGVs if used in userspace
*
* Opcodes which need some work to be supported:
* cd - int N.
* Used by userspace for "int 80" syscall entry. (Other "int N"
* cause GP -> SEGV since their IDT gates don't allow calls from CPL 3).
* Not supported since kernel's handling of userspace single-stepping
* (TF flag) is fragile.
* cf - iret. Normally not used in userspace. Doesn't SEGV unless arguments are bad
*/
#if defined([31mCONFIG_X86_64[0m)
static volatile 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, 1) | /* 00 */
W(0x10, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 10 */
W(0x20, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) | /* 20 */
W(0x30, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
W(0x60, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
W(0x80, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
W(0xd0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0) | /* e0 */
W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */
/* ---------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
#else
#define good_insns_64 NULL
#endif
/* Using this for both 64-bit and 32-bit apps.
* Opcodes we don't support:
* 0f 00 - SLDT/STR/LLDT/LTR/VERR/VERW/-/- group. System insns
* 0f 01 - SGDT/SIDT/LGDT/LIDT/SMSW/-/LMSW/INVLPG group.
* Also encodes tons of other system insns if mod=11.
* Some are in fact non-system: xend, xtest, rdtscp, maybe more
* 0f 05 - syscall
* 0f 06 - clts (CPL0 insn)
* 0f 07 - sysret
* 0f 08 - invd (CPL0 insn)
* 0f 09 - wbinvd (CPL0 insn)
* 0f 0b - ud2
* 0f 30 - wrmsr (CPL0 insn) (then why rdmsr is allowed, it's also CPL0 insn?)
* 0f 34 - sysenter
* 0f 35 - sysexit
* 0f 37 - getsec
* 0f 78 - vmread (Intel VMX. CPL0 insn)
* 0f 79 - vmwrite (Intel VMX. CPL0 insn)
* Note: with prefixes, these two opcodes are
* extrq/insertq/AVX512 convert vector ops.
* 0f ae - group15: [f]xsave,[f]xrstor,[v]{ld,st}mxcsr,clflush[opt],
* {rd,wr}{fs,gs}base,{s,l,m}fence.
* Why? They are all user-executable.
*/
static volatile 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, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1) | /* 00 */
W(0x10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 10 */
W(0x20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */
W(0x30, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 60 */
W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1) , /* 70 */
W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
W(0xe0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* e0 */
W(0xf0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) /* f0 */
/* ---------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
#undef W
/*
* 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
*
* 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 --
* but 64 and 65 (fs: and gs:) seem to be used, so we support them
* 67 - addr16 prefix
* ce - into
* f0 - lock prefix
*/
/*
* TODO:
* - Where necessary, examine the modrm byte and allow only valid instructions
* in the different Groups and fpu instructions.
*/
static bool is_prefix_bad(struct insn *insn)
{
int i;
for (i = 0; i < insn->prefixes.nbytes; i++) {
insn_attr_t attr;
attr = inat_get_opcode_attribute(insn->prefixes.bytes[i]);
switch (attr) {
case INAT_MAKE_PREFIX(INAT_PFX_ES):
case INAT_MAKE_PREFIX(INAT_PFX_CS):
case INAT_MAKE_PREFIX(INAT_PFX_DS):
case INAT_MAKE_PREFIX(INAT_PFX_SS):
case INAT_MAKE_PREFIX(INAT_PFX_LOCK):
return true;
}
}
return false;
}
static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool x86_64)
{
u32 volatile *good_insns;
insn_init(insn, auprobe->insn, sizeof(auprobe->insn), x86_64);
/* has the side-effect of processing the entire instruction */
insn_get_length(insn);
if (!insn_complete(insn))
return -ENOEXEC;
if (is_prefix_bad(insn))
return -ENOTSUPP;
/* We should not singlestep on the exception masking instructions */
if (insn_masking_exception(insn))
return -ENOTSUPP;
if (x86_64)
good_insns = good_insns_64;
else
good_insns = good_insns_32;
if (test_bit(OPCODE1(insn), (unsigned long *)good_insns))
return 0;
if (insn->opcode.nbytes == 2) {
if (test_bit(OPCODE2(insn), (unsigned long *)good_2byte_insns))
return 0;
}
return -ENOTSUPP;
}
#ifdef [31mCONFIG_X86_64[0m
/*
* If arch_uprobe->insn doesn't use rip-relative addressing, return
* immediately. Otherwise, rewrite the instruction so that it accesses
* its memory operand indirectly through a scratch register. Set
* defparam->fixups accordingly. (The contents of the scratch register
* will be saved before we single-step the modified instruction,
* and restored afterward).
*
* We do this because a rip-relative instruction can access only a
* relatively small area (+/- 2 GB from the instruction), and the XOL
* area typically lies beyond that area. At least for instructions
* that store to memory, we can't execute the original instruction
* and "fix things up" later, because the misdirected store could be
* disastrous.
*
* Some useful facts about rip-relative instructions:
*
* - There's always a modrm byte with bit layout "00 reg 101".
* - There's never a SIB byte.
* - The displacement is always 4 bytes.
* - REX.B=1 bit in REX prefix, which normally extends r/m field,
* has no effect on rip-relative mode. It doesn't make modrm byte
* with r/m=101 refer to register 1101 = R13.
*/
static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
{
u8 *cursor;
u8 reg;
u8 reg2;
if (!insn_rip_relative(insn))
return;
/*
* insn_rip_relative() would have decoded rex_prefix, vex_prefix, modrm.
* Clear REX.b bit (extension of MODRM.rm field):
* we want to encode low numbered reg, not r8+.
*/
if (insn->rex_prefix.nbytes) {
cursor = auprobe->insn + insn_offset_rex_prefix(insn);
/* REX byte has 0100wrxb layout, clearing REX.b bit */
*cursor &= 0xfe;
}
/*
* Similar treatment for VEX3/EVEX prefix.
* TODO: add XOP treatment when insn decoder supports them
*/
if (insn->vex_prefix.nbytes >= 3) {
/*
* vex2: c5 rvvvvLpp (has no b bit)
* vex3/xop: c4/8f rxbmmmmm wvvvvLpp
* evex: 62 rxbR00mm wvvvv1pp zllBVaaa
* Setting VEX3.b (setting because it has inverted meaning).
* Setting EVEX.x since (in non-SIB encoding) EVEX.x
* is the 4th bit of MODRM.rm, and needs the same treatment.
* For VEX3-encoded insns, VEX3.x value has no effect in
* non-SIB encoding, the change is superfluous but harmless.
*/
cursor = auprobe->insn + insn_offset_vex_prefix(insn) + 1;
*cursor |= 0x60;
}
/*
* Convert from rip-relative addressing to register-relative addressing
* via a scratch register.
*
* This is tricky since there are insns with modrm byte
* which also use registers not encoded in modrm byte:
* [i]div/[i]mul: implicitly use dx:ax
* shift ops: implicitly use cx
* cmpxchg: implicitly uses ax
* cmpxchg8/16b: implicitly uses dx:ax and bx:cx
* Encoding: 0f c7/1 modrm
* The code below thinks that reg=1 (cx), chooses si as scratch.
* mulx: implicitly uses dx: mulx r/m,r1,r2 does r1:r2 = dx * r/m.
* First appeared in Haswell (BMI2 insn). It is vex-encoded.
* Example where none of bx,cx,dx can be used as scratch reg:
* c4 e2 63 f6 0d disp32 mulx disp32(%rip),%ebx,%ecx
* [v]pcmpistri: implicitly uses cx, xmm0
* [v]pcmpistrm: implicitly uses xmm0
* [v]pcmpestri: implicitly uses ax, dx, cx, xmm0
* [v]pcmpestrm: implicitly uses ax, dx, xmm0
* Evil SSE4.2 string comparison ops from hell.
* maskmovq/[v]maskmovdqu: implicitly uses (ds:rdi) as destination.
* Encoding: 0f f7 modrm, 66 0f f7 modrm, vex-encoded: c5 f9 f7 modrm.
* Store op1, byte-masked by op2 msb's in each byte, to (ds:rdi).
* AMD says it has no 3-operand form (vex.vvvv must be 1111)
* and that it can have only register operands, not mem
* (its modrm byte must have mode=11).
* If these restrictions will ever be lifted,
* we'll need code to prevent selection of di as scratch reg!
*
* Summary: I don't know any insns with modrm byte which
* use SI register implicitly. DI register is used only
* by one insn (maskmovq) and BX register is used
* only by one too (cmpxchg8b).
* BP is stack-segment based (may be a problem?).
* AX, DX, CX are off-limits (many implicit users).
* SP is unusable (it's stack pointer - think about "pop mem";
* also, rsp+disp32 needs sib encoding -> insn length change).
*/
reg = MODRM_REG(insn); /* Fetch modrm.reg */
reg2 = 0xff; /* Fetch vex.vvvv */
if (insn->vex_prefix.nbytes)
reg2 = insn->vex_prefix.bytes[2];
/*
* TODO: add XOP vvvv reading.
*
* vex.vvvv field is in bits 6-3, bits are inverted.
* But in 32-bit mode, high-order bit may be ignored.
* Therefore, let's consider only 3 low-order bits.
*/
reg2 = ((reg2 >> 3) & 0x7) ^ 0x7;
/*
* Register numbering is ax,cx,dx,bx, sp,bp,si,di, r8..r15.
*
* Choose scratch reg. Order is important: must not select bx
* if we can use si (cmpxchg8b case!)
*/
if (reg != 6 && reg2 != 6) {
reg2 = 6;
auprobe->defparam.fixups |= UPROBE_FIX_RIP_SI;
} else if (reg != 7 && reg2 != 7) {
reg2 = 7;
auprobe->defparam.fixups |= UPROBE_FIX_RIP_DI;
/* TODO (paranoia): force maskmovq to not use di */
} else {
reg2 = 3;
auprobe->defparam.fixups |= UPROBE_FIX_RIP_BX;
}
/*
* Point cursor at the modrm byte. The next 4 bytes are the
* displacement. Beyond the displacement, for some instructions,
* is the immediate operand.
*/
cursor = auprobe->insn + insn_offset_modrm(insn);
/*
* Change modrm from "00 reg 101" to "10 reg reg2". Example:
* 89 05 disp32 mov %eax,disp32(%rip) becomes
* 89 86 disp32 mov %eax,disp32(%rsi)
*/
*cursor = 0x80 | (reg << 3) | reg2;
}
static inline unsigned long *
scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_SI)
return ®s->si;
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_DI)
return ®s->di;
return ®s->bx;
}
/*
* If we're emulating a rip-relative instruction, save the contents
* of the scratch register and store the target address in that register.
*/
static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_MASK) {
struct uprobe_task *utask = current->utask;
unsigned long *sr = scratch_reg(auprobe, regs);
utask->autask.saved_scratch_register = *sr;
*sr = utask->vaddr + auprobe->defparam.ilen;
}
}
static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (auprobe->defparam.fixups & UPROBE_FIX_RIP_MASK) {
struct uprobe_task *utask = current->utask;
unsigned long *sr = scratch_reg(auprobe, regs);
*sr = utask->autask.saved_scratch_register;
}
}
#else /* 32-bit: */
/*
* No RIP-relative addressing on 32-bit
*/
static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
{
}
static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
}
static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
}
#endif /* CONFIG_X86_64 */
struct uprobe_xol_ops {
bool (*emulate)(struct arch_uprobe *, struct pt_regs *);
int (*pre_xol)(struct arch_uprobe *, struct pt_regs *);
int (*post_xol)(struct arch_uprobe *, struct pt_regs *);
void (*abort)(struct arch_uprobe *, struct pt_regs *);
};
static inline int sizeof_long(struct pt_regs *regs)
{
/*
* Check registers for mode as in_xxx_syscall() does not apply here.
*/
return user_64bit_mode(regs) ? 8 : 4;
}
static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
riprel_pre_xol(auprobe, regs);
return 0;
}
static int emulate_push_stack(struct pt_regs *regs, unsigned long val)
{
unsigned long new_sp = regs->sp - sizeof_long(regs);
if (copy_to_user((void __user *)new_sp, &val, sizeof_long(regs)))
return -EFAULT;
regs->sp = new_sp;
return 0;
}
/*
* We have to fix things up as follows:
*
* Typically, the new ip is relative to the copied instruction. We need
* to make it relative to the original instruction (FIX_IP). Exceptions
* are return instructions and absolute or indirect jump or call instructions.
*
* If the single-stepped instruction was a call, the return address that
* is atop the stack is the address following the copied instruction. We
* need to make it the address following the original instruction (FIX_CALL).
*
* If the original instruction was a rip-relative instruction such as
* "movl %edx,0xnnnn(%rip)", we have instead executed an equivalent
* instruction using a scratch register -- e.g., "movl %edx,0xnnnn(%rsi)".
* We need to restore the contents of the scratch register
* (FIX_RIP_reg).
*/
static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
riprel_post_xol(auprobe, regs);
if (auprobe->defparam.fixups & UPROBE_FIX_IP) {
long correction = utask->vaddr - utask->xol_vaddr;
regs->ip += correction;
} else if (auprobe->defparam.fixups & UPROBE_FIX_CALL) {
regs->sp += sizeof_long(regs); /* Pop incorrect return address */
if (emulate_push_stack(regs, utask->vaddr + auprobe->defparam.ilen))
return -ERESTART;
}
/* popf; tell the caller to not touch TF */
if (auprobe->defparam.fixups & UPROBE_FIX_SETF)
utask->autask.saved_tf = true;
return 0;
}
static void default_abort_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
riprel_post_xol(auprobe, regs);
}
static const struct uprobe_xol_ops default_xol_ops = {
.pre_xol = default_pre_xol_op,
.post_xol = default_post_xol_op,
.abort = default_abort_op,
};
static bool branch_is_call(struct arch_uprobe *auprobe)
{
return auprobe->branch.opc1 == 0xe8;
}
#define CASE_COND \
COND(70, 71, XF(OF)) \
COND(72, 73, XF(CF)) \
COND(74, 75, XF(ZF)) \
COND(78, 79, XF(SF)) \
COND(7a, 7b, XF(PF)) \
COND(76, 77, XF(CF) || XF(ZF)) \
COND(7c, 7d, XF(SF) != XF(OF)) \
COND(7e, 7f, XF(ZF) || XF(SF) != XF(OF))
#define COND(op_y, op_n, expr) \
case 0x ## op_y: DO((expr) != 0) \
case 0x ## op_n: DO((expr) == 0)
#define XF(xf) (!!(flags & X86_EFLAGS_ ## xf))
static bool is_cond_jmp_opcode(u8 opcode)
{
switch (opcode) {
#define DO(expr) \
return true;
CASE_COND
#undef DO
default:
return false;
}
}
static bool check_jmp_cond(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
unsigned long flags = regs->flags;
switch (auprobe->branch.opc1) {
#define DO(expr) \
return expr;
CASE_COND
#undef DO
default: /* not a conditional jmp */
return true;
}
}
#undef XF
#undef COND
#undef CASE_COND
static bool branch_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
unsigned long new_ip = regs->ip += auprobe->branch.ilen;
unsigned long offs = (long)auprobe->branch.offs;
if (branch_is_call(auprobe)) {
/*
* If it fails we execute this (mangled, see the comment in
* branch_clear_offset) insn out-of-line. In the likely case
* this should trigger the trap, and the probed application
* should die or restart the same insn after it handles the
* signal, arch_uprobe_post_xol() won't be even called.
*
* But there is corner case, see the comment in ->post_xol().
*/
if (emulate_push_stack(regs, new_ip))
return false;
} else if (!check_jmp_cond(auprobe, regs)) {
offs = 0;
}
regs->ip = new_ip + offs;
return true;
}
static bool push_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
unsigned long *src_ptr = (void *)regs + auprobe->push.reg_offset;
if (emulate_push_stack(regs, *src_ptr))
return false;
regs->ip += auprobe->push.ilen;
return true;
}
static int branch_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
BUG_ON(!branch_is_call(auprobe));
/*
* We can only get here if branch_emulate_op() failed to push the ret
* address _and_ another thread expanded our stack before the (mangled)
* "call" insn was executed out-of-line. Just restore ->sp and restart.
* We could also restore ->ip and try to call branch_emulate_op() again.
*/
regs->sp += sizeof_long(regs);
return -ERESTART;
}
static void branch_clear_offset(struct arch_uprobe *auprobe, struct insn *insn)
{
/*
* Turn this insn into "call 1f; 1:", this is what we will execute
* out-of-line if ->emulate() fails. We only need this to generate
* a trap, so that the probed task receives the correct signal with
* the properly filled siginfo.
*
* But see the comment in ->post_xol(), in the unlikely case it can
* succeed. So we need to ensure that the new ->ip can not fall into
* the non-canonical area and trigger #GP.
*
* We could turn it into (say) "pushf", but then we would need to
* divorce ->insn[] and ->ixol[]. We need to preserve the 1st byte
* of ->insn[] for set_orig_insn().
*/
memset(auprobe->insn + insn_offset_immediate(insn),
0, insn->immediate.nbytes);
}
static const struct uprobe_xol_ops branch_xol_ops = {
.emulate = branch_emulate_op,
.post_xol = branch_post_xol_op,
};
static const struct uprobe_xol_ops push_xol_ops = {
.emulate = push_emulate_op,
};
/* Returns -ENOSYS if branch_xol_ops doesn't handle this insn */
static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
{
u8 opc1 = OPCODE1(insn);
int i;
switch (opc1) {
case 0xeb: /* jmp 8 */
case 0xe9: /* jmp 32 */
case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
break;
case 0xe8: /* call relative */
branch_clear_offset(auprobe, insn);
break;
case 0x0f:
if (insn->opcode.nbytes != 2)
return -ENOSYS;
/*
* If it is a "near" conditional jmp, OPCODE2() - 0x10 matches
* OPCODE1() of the "short" jmp which checks the same condition.
*/
opc1 = OPCODE2(insn) - 0x10;
/* fall through */
default:
if (!is_cond_jmp_opcode(opc1))
return -ENOSYS;
}
/*
* 16-bit overrides such as CALLW (66 e8 nn nn) are not supported.
* Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix.
* No one uses these insns, reject any branch insns with such prefix.
*/
for (i = 0; i < insn->prefixes.nbytes; i++) {
if (insn->prefixes.bytes[i] == 0x66)
return -ENOTSUPP;
}
auprobe->branch.opc1 = opc1;
auprobe->branch.ilen = insn->length;
auprobe->branch.offs = insn->immediate.value;
auprobe->ops = &branch_xol_ops;
return 0;
}
/* Returns -ENOSYS if push_xol_ops doesn't handle this insn */
static int push_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
{
u8 opc1 = OPCODE1(insn), reg_offset = 0;
if (opc1 < 0x50 || opc1 > 0x57)
return -ENOSYS;
if (insn->length > 2)
return -ENOSYS;
if (insn->length == 2) {
/* only support rex_prefix 0x41 (x64 only) */
#ifdef [31mCONFIG_X86_64[0m
if (insn->rex_prefix.nbytes != 1 ||
insn->rex_prefix.bytes[0] != 0x41)
return -ENOSYS;
switch (opc1) {
case 0x50:
reg_offset = offsetof(struct pt_regs, r8);
break;
case 0x51:
reg_offset = offsetof(struct pt_regs, r9);
break;
case 0x52:
reg_offset = offsetof(struct pt_regs, r10);
break;
case 0x53:
reg_offset = offsetof(struct pt_regs, r11);
break;
case 0x54:
reg_offset = offsetof(struct pt_regs, r12);
break;
case 0x55:
reg_offset = offsetof(struct pt_regs, r13);
break;
case 0x56:
reg_offset = offsetof(struct pt_regs, r14);
break;
case 0x57:
reg_offset = offsetof(struct pt_regs, r15);
break;
}
#else
return -ENOSYS;
#endif
} else {
switch (opc1) {
case 0x50:
reg_offset = offsetof(struct pt_regs, ax);
break;
case 0x51:
reg_offset = offsetof(struct pt_regs, cx);
break;
case 0x52:
reg_offset = offsetof(struct pt_regs, dx);
break;
case 0x53:
reg_offset = offsetof(struct pt_regs, bx);
break;
case 0x54:
reg_offset = offsetof(struct pt_regs, sp);
break;
case 0x55:
reg_offset = offsetof(struct pt_regs, bp);
break;
case 0x56:
reg_offset = offsetof(struct pt_regs, si);
break;
case 0x57:
reg_offset = offsetof(struct pt_regs, di);
break;
}
}
auprobe->push.reg_offset = reg_offset;
auprobe->push.ilen = insn->length;
auprobe->ops = &push_xol_ops;
return 0;
}
/**
* arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
* @mm: the probed address space.
* @arch_uprobe: the probepoint information.
* @addr: virtual address at which to install the probepoint
* Return 0 on success or a -ve number on error.
*/
int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr)
{
struct insn insn;
u8 fix_ip_or_call = UPROBE_FIX_IP;
int ret;
ret = uprobe_init_insn(auprobe, &insn, is_64bit_mm(mm));
if (ret)
return ret;
ret = branch_setup_xol_ops(auprobe, &insn);
if (ret != -ENOSYS)
return ret;
ret = push_setup_xol_ops(auprobe, &insn);
if (ret != -ENOSYS)
return ret;
/*
* Figure out which fixups default_post_xol_op() will need to perform,
* and annotate defparam->fixups accordingly.
*/
switch (OPCODE1(&insn)) {
case 0x9d: /* popf */
auprobe->defparam.fixups |= UPROBE_FIX_SETF;
break;
case 0xc3: /* ret or lret -- ip is correct */
case 0xcb:
case 0xc2:
case 0xca:
case 0xea: /* jmp absolute -- ip is correct */
fix_ip_or_call = 0;
break;
case 0x9a: /* call absolute - Fix return addr, not ip */
fix_ip_or_call = UPROBE_FIX_CALL;
break;
case 0xff:
switch (MODRM_REG(&insn)) {
case 2: case 3: /* call or lcall, indirect */
fix_ip_or_call = UPROBE_FIX_CALL;
break;
case 4: case 5: /* jmp or ljmp, indirect */
fix_ip_or_call = 0;
break;
}
/* fall through */
default:
riprel_analyze(auprobe, &insn);
}
auprobe->defparam.ilen = insn.length;
auprobe->defparam.fixups |= fix_ip_or_call;
auprobe->ops = &default_xol_ops;
return 0;
}
/*
* arch_uprobe_pre_xol - prepare to execute out of line.
* @auprobe: the probepoint information.
* @regs: reflects the saved user state of current task.
*/
int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
if (auprobe->ops->pre_xol) {
int err = auprobe->ops->pre_xol(auprobe, regs);
if (err)
return err;
}
regs->ip = utask->xol_vaddr;
utask->autask.saved_trap_nr = current->thread.trap_nr;
current->thread.trap_nr = UPROBE_TRAP_NR;
utask->autask.saved_tf = !!(regs->flags & X86_EFLAGS_TF);
regs->flags |= X86_EFLAGS_TF;
if (test_tsk_thread_flag(current, TIF_BLOCKSTEP))
set_task_blockstep(current, false);
return 0;
}
/*
* If xol insn itself traps and generates a signal(Say,
* SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
* instruction jumps back to its own address. It is assumed that anything
* like do_page_fault/do_trap/etc sets thread.trap_nr != -1.
*
* arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
* arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
* UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
*/
bool arch_uprobe_xol_was_trapped(struct task_struct *t)
{
if (t->thread.trap_nr != UPROBE_TRAP_NR)
return true;
return false;
}
/*
* Called after single-stepping. 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.
*
* This function prepares to resume execution after the single-step.
*/
int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
bool send_sigtrap = utask->autask.saved_tf;
int err = 0;
WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
current->thread.trap_nr = utask->autask.saved_trap_nr;
if (auprobe->ops->post_xol) {
err = auprobe->ops->post_xol(auprobe, regs);
if (err) {
/*
* Restore ->ip for restart or post mortem analysis.
* ->post_xol() must not return -ERESTART unless this
* is really possible.
*/
regs->ip = utask->vaddr;
if (err == -ERESTART)
err = 0;
send_sigtrap = false;
}
}
/*
* arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
* so we can get an extra SIGTRAP if we do not clear TF. We need
* to examine the opcode to make it right.
*/
if (send_sigtrap)
send_sig(SIGTRAP, current, 0);
if (!utask->autask.saved_tf)
regs->flags &= ~X86_EFLAGS_TF;
return err;
}
/* callback routine for handling exceptions. */
int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
{
struct die_args *args = data;
struct pt_regs *regs = args->regs;
int ret = NOTIFY_DONE;
/* We are only interested in userspace traps */
if (regs && !user_mode(regs))
return NOTIFY_DONE;
switch (val) {
case DIE_INT3:
if (uprobe_pre_sstep_notifier(regs))
ret = NOTIFY_STOP;
break;
case DIE_DEBUG:
if (uprobe_post_sstep_notifier(regs))
ret = NOTIFY_STOP;
default:
break;
}
return ret;
}
/*
* This function gets called when XOL instruction either gets trapped or
* the thread has a fatal signal. Reset the instruction pointer to its
* probed address for the potential restart or for post mortem analysis.
*/
void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
if (auprobe->ops->abort)
auprobe->ops->abort(auprobe, regs);
current->thread.trap_nr = utask->autask.saved_trap_nr;
regs->ip = utask->vaddr;
/* clear TF if it was set by us in arch_uprobe_pre_xol() */
if (!utask->autask.saved_tf)
regs->flags &= ~X86_EFLAGS_TF;
}
static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
if (auprobe->ops->emulate)
return auprobe->ops->emulate(auprobe, regs);
return false;
}
bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
bool ret = __skip_sstep(auprobe, regs);
if (ret && (regs->flags & X86_EFLAGS_TF))
send_sig(SIGTRAP, current, 0);
return ret;
}
unsigned long
arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs)
{
int rasize = sizeof_long(regs), nleft;
unsigned long orig_ret_vaddr = 0; /* clear high bits for 32-bit apps */
if (copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp, rasize))
return -1;
/* check whether address has been already hijacked */
if (orig_ret_vaddr == trampoline_vaddr)
return orig_ret_vaddr;
nleft = copy_to_user((void __user *)regs->sp, &trampoline_vaddr, rasize);
if (likely(!nleft))
return orig_ret_vaddr;
if (nleft != rasize) {
pr_err("return address clobbered: pid=%d, %%sp=%#lx, %%ip=%#lx\n",
current->pid, regs->sp, regs->ip);
force_sig(SIGSEGV);
}
return -1;
}
bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
struct pt_regs *regs)
{
if (ctx == RP_CHECK_CALL) /* sp was just decremented by "call" insn */
return regs->sp < ret->stack;
else
return regs->sp <= ret->stack;
}