/* * 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 #include #include #include #include #include #include #include /* Post-execution fixups. */ /* Adjust IP back to vicinity of actual insn */ #define UPROBE_FIX_IP 0x1 /* Adjust the return address of a call insn */ #define UPROBE_FIX_CALL 0x2 /* Instruction will modify TF, don't change it */ #define UPROBE_FIX_SETF 0x4 #define UPROBE_FIX_RIP_AX 0x8000 #define UPROBE_FIX_RIP_CX 0x4000 #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. */ #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, 0) | /* 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, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1) | /* 20 */ W(0x30, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 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, 0, 1, 1, 0, 0, 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, 0, 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, 0, 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 */ #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, 0) | /* 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, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) | /* 20 */ W(0x30, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 30 */ W(0x40, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 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, 0, 0, 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, 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, 0, 0, 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, 1, 1, 0, 0, 0, 0) | /* e0 */ W(0xf0, 0, 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 */ 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1) | /* 00 */ W(0x10, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1) , /* 10 */ W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */ W(0x30, 0, 1, 1, 1, 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, 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, 0, 0, 0, 0, 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, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1) | /* a0 */ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 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, 0, 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, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0) /* f0 */ /* ---------------------------------------------- */ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ }; #undef W /* * opcodes we'll probably never support: * * 6c-6d, e4-e5, ec-ed - in * 6e-6f, e6-e7, ee-ef - out * cc, cd - int3, int * cf - iret * d6 - illegal instruction * f1 - int1/icebp * f4 - hlt * fa, fb - cli, sti * 0f - lar, lsl, syscall, clts, sysret, sysenter, sysexit, invd, wbinvd, ud2 * * invalid opcodes in 64-bit mode: * * 06, 0e, 16, 1e, 27, 2f, 37, 3f, 60-62, 82, c4-c5, d4-d5 * 63 - we support this opcode in x86_64 but not in i386. * * 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, 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 static inline bool is_64bit_mm(struct mm_struct *mm) { return !config_enabled(CONFIG_IA32_EMULATION) || !(mm->context.ia32_compat == TIF_IA32); } /* * 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 * arch_uprobe->fixups and arch_uprobe->rip_rela_target_address * 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. * - There's never a SIB byte. * - The displacement is always 4 bytes. */ static void handle_riprel_insn(struct arch_uprobe *auprobe, struct insn *insn) { u8 *cursor; u8 reg; if (!insn_rip_relative(insn)) return; /* * insn_rip_relative() would have decoded rex_prefix, modrm. * Clear REX.b bit (extension of MODRM.rm field): * we want to encode rax/rcx, not r8/r9. */ if (insn->rex_prefix.nbytes) { cursor = auprobe->insn + insn_offset_rex_prefix(insn); *cursor &= 0xfe; /* Clearing REX.B bit */ } /* * 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); /* * Convert from rip-relative addressing to indirect addressing * via a scratch register. Change the r/m field from 0x5 (%rip) * to 0x0 (%rax) or 0x1 (%rcx), and squeeze out the offset field. */ reg = MODRM_REG(insn); if (reg == 0) { /* * The register operand (if any) is either the A register * (%rax, %eax, etc.) or (if the 0x4 bit is set in the * REX prefix) %r8. In any case, we know the C register * is NOT the register operand, so we use %rcx (register * #1) for the scratch register. */ auprobe->fixups = UPROBE_FIX_RIP_CX; /* Change modrm from 00 000 101 to 00 000 001. */ *cursor = 0x1; } else { /* Use %rax (register #0) for the scratch register. */ auprobe->fixups = UPROBE_FIX_RIP_AX; /* Change modrm from 00 xxx 101 to 00 xxx 000 */ *cursor = (reg << 3); } /* Target address = address of next instruction + (signed) offset */ auprobe->rip_rela_target_address = (long)insn->length + insn->displacement.value; /* Displacement field is gone; slide immediate field (if any) over. */ if (insn->immediate.nbytes) { cursor++; memmove(cursor, cursor + insn->displacement.nbytes, insn->immediate.nbytes); } } /* * 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 pre_xol_rip_insn(struct arch_uprobe *auprobe, struct pt_regs *regs, struct arch_uprobe_task *autask) { if (auprobe->fixups & UPROBE_FIX_RIP_AX) { autask->saved_scratch_register = regs->ax; regs->ax = current->utask->vaddr; regs->ax += auprobe->rip_rela_target_address; } else if (auprobe->fixups & UPROBE_FIX_RIP_CX) { autask->saved_scratch_register = regs->cx; regs->cx = current->utask->vaddr; regs->cx += auprobe->rip_rela_target_address; } } static void handle_riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, long *correction) { if (auprobe->fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) { struct arch_uprobe_task *autask; autask = ¤t->utask->autask; if (auprobe->fixups & UPROBE_FIX_RIP_AX) regs->ax = autask->saved_scratch_register; else regs->cx = autask->saved_scratch_register; /* * The original instruction includes a displacement, and so * is 4 bytes longer than what we've just single-stepped. * Caller may need to apply other fixups to handle stuff * like "jmpq *...(%rip)" and "callq *...(%rip)". */ if (correction) *correction += 4; } } #else /* 32-bit: */ static inline bool is_64bit_mm(struct mm_struct *mm) { return false; } /* * No RIP-relative addressing on 32-bit */ static void handle_riprel_insn(struct arch_uprobe *auprobe, struct insn *insn) { } static void pre_xol_rip_insn(struct arch_uprobe *auprobe, struct pt_regs *regs, struct arch_uprobe_task *autask) { } static void handle_riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, long *correction) { } #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) { pre_xol_rip_insn(auprobe, regs, ¤t->utask->autask); return 0; } /* * Adjust the return address pushed by a call insn executed out of line. */ static int adjust_ret_addr(unsigned long sp, long correction) { int rasize = sizeof_long(); long ra; if (copy_from_user(&ra, (void __user *)sp, rasize)) return -EFAULT; ra += correction; if (copy_to_user((void __user *)sp, &ra, rasize)) return -EFAULT; return 0; } static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs) { struct uprobe_task *utask = current->utask; long correction = (long)(utask->vaddr - utask->xol_vaddr); handle_riprel_post_xol(auprobe, regs, &correction); if (auprobe->fixups & UPROBE_FIX_IP) regs->ip += correction; if (auprobe->fixups & UPROBE_FIX_CALL) { if (adjust_ret_addr(regs->sp, correction)) { regs->sp += sizeof_long(); return -ERESTART; } } /* popf; tell the caller to not touch TF */ if (auprobe->fixups & UPROBE_FIX_SETF) utask->autask.saved_tf = true; return 0; } static void default_abort_op(struct arch_uprobe *auprobe, struct pt_regs *regs) { handle_riprel_post_xol(auprobe, regs, NULL); } 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)) { unsigned long new_sp = regs->sp - sizeof_long(); /* * 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 (copy_to_user((void __user *)new_sp, &new_ip, sizeof_long())) return false; regs->sp = new_sp; } 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; bool fix_ip = true, fix_call = false; 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 arch_uprobe_post_xol() will need to perform, * and annotate arch_uprobe->fixups accordingly. To start with, ->fixups * is either zero or it reflects rip-related fixups. */ switch (OPCODE1(&insn)) { case 0x9d: /* popf */ auprobe->fixups |= UPROBE_FIX_SETF; break; case 0xc3: /* ret or lret -- ip is correct */ case 0xcb: case 0xc2: case 0xca: fix_ip = false; break; case 0x9a: /* call absolute - Fix return addr, not ip */ fix_call = true; fix_ip = false; break; case 0xea: /* jmp absolute -- ip is correct */ fix_ip = false; break; case 0xff: switch (MODRM_REG(&insn)) { case 2: case 3: /* call or lcall, indirect */ fix_call = true; case 4: case 5: /* jmp or ljmp, indirect */ fix_ip = false; } /* fall through */ default: handle_riprel_insn(auprobe, &insn); } if (fix_ip) auprobe->fixups |= UPROBE_FIX_IP; if (fix_call) auprobe->fixups |= UPROBE_FIX_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. * 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,(%rax)". * We need to restore the contents of the scratch register and adjust * the ip, keeping in mind that the instruction we executed is 4 bytes * shorter than the original instruction (since we squeezed out the offset * field). (FIX_RIP_AX or FIX_RIP_CX) */ 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_vm(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; }