diff options
| -rw-r--r-- | arch/x86/lib/insn-eval.c | 243 |
1 files changed, 185 insertions, 58 deletions
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 91f08aa..a4427b4 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -776,6 +776,182 @@ static int get_seg_base_limit(struct insn *insn, struct pt_regs *regs, return 0; } +/** + * get_eff_addr_reg() - Obtain effective address from register operand + * @insn: Instruction. Must be valid. + * @regs: Register values as seen when entering kernel mode + * @regoff: Obtained operand offset, in pt_regs, with the effective address + * @eff_addr: Obtained effective address + * + * Obtain the effective address stored in the register operand as indicated by + * the ModRM byte. This function is to be used only with register addressing + * (i.e., ModRM.mod is 3). The effective address is saved in @eff_addr. The + * register operand, as an offset from the base of pt_regs, is saved in @regoff; + * such offset can then be used to resolve the segment associated with the + * operand. This function can be used with any of the supported address sizes + * in x86. + * + * Returns: + * + * 0 on success. @eff_addr will have the effective address stored in the + * operand indicated by ModRM. @regoff will have such operand as an offset from + * the base of pt_regs. + * + * -EINVAL on error. + */ +static int get_eff_addr_reg(struct insn *insn, struct pt_regs *regs, + int *regoff, long *eff_addr) +{ + insn_get_modrm(insn); + + if (!insn->modrm.nbytes) + return -EINVAL; + + if (X86_MODRM_MOD(insn->modrm.value) != 3) + return -EINVAL; + + *regoff = get_reg_offset(insn, regs, REG_TYPE_RM); + if (*regoff < 0) + return -EINVAL; + + *eff_addr = regs_get_register(regs, *regoff); + + return 0; +} + +/** + * get_eff_addr_modrm() - Obtain referenced effective address via ModRM + * @insn: Instruction. Must be valid. + * @regs: Register values as seen when entering kernel mode + * @regoff: Obtained operand offset, in pt_regs, associated with segment + * @eff_addr: Obtained effective address + * + * Obtain the effective address referenced by the ModRM byte of @insn. After + * identifying the registers involved in the register-indirect memory reference, + * its value is obtained from the operands in @regs. The computed address is + * stored @eff_addr. Also, the register operand that indicates the associated + * segment is stored in @regoff, this parameter can later be used to determine + * such segment. + * + * Returns: + * + * 0 on success. @eff_addr will have the referenced effective address. @regoff + * will have a register, as an offset from the base of pt_regs, that can be used + * to resolve the associated segment. + * + * -EINVAL on error. + */ +static int get_eff_addr_modrm(struct insn *insn, struct pt_regs *regs, + int *regoff, long *eff_addr) +{ + long tmp; + + if (insn->addr_bytes != 8) + return -EINVAL; + + insn_get_modrm(insn); + + if (!insn->modrm.nbytes) + return -EINVAL; + + if (X86_MODRM_MOD(insn->modrm.value) > 2) + return -EINVAL; + + *regoff = get_reg_offset(insn, regs, REG_TYPE_RM); + + /* + * -EDOM means that we must ignore the address_offset. In such a case, + * in 64-bit mode the effective address relative to the rIP of the + * following instruction. + */ + if (*regoff == -EDOM) { + if (user_64bit_mode(regs)) + tmp = regs->ip + insn->length; + else + tmp = 0; + } else if (*regoff < 0) { + return -EINVAL; + } else { + tmp = regs_get_register(regs, *regoff); + } + + *eff_addr = tmp + insn->displacement.value; + + return 0; +} + +/** + * get_eff_addr_sib() - Obtain referenced effective address via SIB + * @insn: Instruction. Must be valid. + * @regs: Register values as seen when entering kernel mode + * @regoff: Obtained operand offset, in pt_regs, associated with segment + * @eff_addr: Obtained effective address + * + * Obtain the effective address referenced by the SIB byte of @insn. After + * identifying the registers involved in the indexed, register-indirect memory + * reference, its value is obtained from the operands in @regs. The computed + * address is stored @eff_addr. Also, the register operand that indicates the + * associated segment is stored in @regoff, this parameter can later be used to + * determine such segment. + * + * Returns: + * + * 0 on success. @eff_addr will have the referenced effective address. + * @base_offset will have a register, as an offset from the base of pt_regs, + * that can be used to resolve the associated segment. + * + * -EINVAL on error. + */ +static int get_eff_addr_sib(struct insn *insn, struct pt_regs *regs, + int *base_offset, long *eff_addr) +{ + long base, indx; + int indx_offset; + + if (insn->addr_bytes != 8) + return -EINVAL; + + insn_get_modrm(insn); + + if (!insn->modrm.nbytes) + return -EINVAL; + + if (X86_MODRM_MOD(insn->modrm.value) > 2) + return -EINVAL; + + insn_get_sib(insn); + + if (!insn->sib.nbytes) + return -EINVAL; + + *base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE); + indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX); + + /* + * Negative values in the base and index offset means an error when + * decoding the SIB byte. Except -EDOM, which means that the registers + * should not be used in the address computation. + */ + if (*base_offset == -EDOM) + base = 0; + else if (*base_offset < 0) + return -EINVAL; + else + base = regs_get_register(regs, *base_offset); + + if (indx_offset == -EDOM) + indx = 0; + else if (indx_offset < 0) + return -EINVAL; + else + indx = regs_get_register(regs, indx_offset); + + *eff_addr = base + indx * (1 << X86_SIB_SCALE(insn->sib.value)); + + *eff_addr += insn->displacement.value; + + return 0; +} /* * return the address being referenced be instruction * for rm=3 returning the content of the rm reg @@ -783,78 +959,29 @@ static int get_seg_base_limit(struct insn *insn, struct pt_regs *regs, */ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) { - int addr_offset, base_offset, indx_offset, ret; unsigned long linear_addr = -1L, seg_base; - long eff_addr, base, indx; - insn_byte_t sib; - - insn_get_modrm(insn); - insn_get_sib(insn); - sib = insn->sib.value; + int regoff, ret; + long eff_addr; if (X86_MODRM_MOD(insn->modrm.value) == 3) { - addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); - if (addr_offset < 0) + ret = get_eff_addr_reg(insn, regs, ®off, &eff_addr); + if (ret) goto out; - eff_addr = regs_get_register(regs, addr_offset); - } else { if (insn->sib.nbytes) { - /* - * Negative values in the base and index offset means - * an error when decoding the SIB byte. Except -EDOM, - * which means that the registers should not be used - * in the address computation. - */ - base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE); - if (base_offset == -EDOM) - base = 0; - else if (base_offset < 0) + ret = get_eff_addr_sib(insn, regs, ®off, &eff_addr); + if (ret) goto out; - else - base = regs_get_register(regs, base_offset); - - indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX); - - if (indx_offset == -EDOM) - indx = 0; - else if (indx_offset < 0) - goto out; - else - indx = regs_get_register(regs, indx_offset); - - eff_addr = base + indx * (1 << X86_SIB_SCALE(sib)); - - /* - * The base determines the segment used to compute - * the linear address. - */ - addr_offset = base_offset; - } else { - addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); - /* - * -EDOM means that we must ignore the address_offset. - * In such a case, in 64-bit mode the effective address - * relative to the RIP of the following instruction. - */ - if (addr_offset == -EDOM) { - if (user_64bit_mode(regs)) - eff_addr = (long)regs->ip + insn->length; - else - eff_addr = 0; - } else if (addr_offset < 0) { + ret = get_eff_addr_modrm(insn, regs, ®off, &eff_addr); + if (ret) goto out; - } else { - eff_addr = regs_get_register(regs, addr_offset); - } } - eff_addr += insn->displacement.value; } - ret = get_seg_base_limit(insn, regs, addr_offset, &seg_base, NULL); + ret = get_seg_base_limit(insn, regs, regoff, &seg_base, NULL); if (ret) goto out; |
