| /* |
| * 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 |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| * |
| * 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(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) |
| 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(CONFIG_X86_64) |
| 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++) { |
| 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 */ |
| 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 (WARN_ON_ONCE(!insn_complete(insn))) |
| return -ENOEXEC; |
| |
| if (is_prefix_bad(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 CONFIG_X86_64 |
| /* |
| * 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(void) |
| { |
| return is_ia32_task() ? 4 : 8; |
| } |
| |
| static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs) |
| { |
| riprel_pre_xol(auprobe, regs); |
| return 0; |
| } |
| |
| static int push_ret_address(struct pt_regs *regs, unsigned long ip) |
| { |
| unsigned long new_sp = regs->sp - sizeof_long(); |
| |
| if (copy_to_user((void __user *)new_sp, &ip, sizeof_long())) |
| 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(); /* Pop incorrect return address */ |
| if (push_ret_address(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 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 (push_ret_address(regs, new_ip)) |
| return false; |
| } else if (!check_jmp_cond(auprobe, regs)) { |
| offs = 0; |
| } |
| |
| regs->ip = new_ip + offs; |
| 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(); |
| 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 struct uprobe_xol_ops branch_xol_ops = { |
| .emulate = branch_emulate_op, |
| .post_xol = branch_post_xol_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; |
| 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; |
| } |
| |
| /** |
| * 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; |
| |
| /* |
| * 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(), 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("uprobe: return address clobbered: pid=%d, %%sp=%#lx, " |
| "%%ip=%#lx\n", current->pid, regs->sp, regs->ip); |
| |
| force_sig_info(SIGSEGV, SEND_SIG_FORCED, current); |
| } |
| |
| 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; |
| } |