2 * Utility functions for x86 operand and address decoding
4 * Copyright (C) Intel Corporation 2017
6 #include <linux/kernel.h>
7 #include <linux/string.h>
8 #include <linux/ratelimit.h>
9 #include <linux/mmu_context.h>
10 #include <asm/desc_defs.h>
14 #include <asm/insn-eval.h>
19 #define pr_fmt(fmt) "insn: " fmt
29 * is_string_insn() - Determine if instruction is a string instruction
30 * @insn: Instruction containing the opcode to inspect
34 * true if the instruction, determined by the opcode, is any of the
35 * string instructions as defined in the Intel Software Development manual.
38 static bool is_string_insn(struct insn *insn)
40 /* All string instructions have a 1-byte opcode. */
41 if (insn->opcode.nbytes != 1)
44 switch (insn->opcode.bytes[0]) {
45 case 0x6c ... 0x6f: /* INS, OUTS */
46 case 0xa4 ... 0xa7: /* MOVS, CMPS */
47 case 0xaa ... 0xaf: /* STOS, LODS, SCAS */
55 * insn_has_rep_prefix() - Determine if instruction has a REP prefix
56 * @insn: Instruction containing the prefix to inspect
60 * true if the instruction has a REP prefix, false if not.
62 bool insn_has_rep_prefix(struct insn *insn)
67 insn_get_prefixes(insn);
69 for_each_insn_prefix(insn, i, p) {
70 if (p == 0xf2 || p == 0xf3)
78 * get_seg_reg_override_idx() - obtain segment register override index
79 * @insn: Valid instruction with segment override prefixes
81 * Inspect the instruction prefixes in @insn and find segment overrides, if any.
85 * A constant identifying the segment register to use, among CS, SS, DS,
86 * ES, FS, or GS. INAT_SEG_REG_DEFAULT is returned if no segment override
87 * prefixes were found.
89 * -EINVAL in case of error.
91 static int get_seg_reg_override_idx(struct insn *insn)
93 int idx = INAT_SEG_REG_DEFAULT;
94 int num_overrides = 0, i;
97 insn_get_prefixes(insn);
99 /* Look for any segment override prefixes. */
100 for_each_insn_prefix(insn, i, p) {
103 attr = inat_get_opcode_attribute(p);
105 case INAT_MAKE_PREFIX(INAT_PFX_CS):
106 idx = INAT_SEG_REG_CS;
109 case INAT_MAKE_PREFIX(INAT_PFX_SS):
110 idx = INAT_SEG_REG_SS;
113 case INAT_MAKE_PREFIX(INAT_PFX_DS):
114 idx = INAT_SEG_REG_DS;
117 case INAT_MAKE_PREFIX(INAT_PFX_ES):
118 idx = INAT_SEG_REG_ES;
121 case INAT_MAKE_PREFIX(INAT_PFX_FS):
122 idx = INAT_SEG_REG_FS;
125 case INAT_MAKE_PREFIX(INAT_PFX_GS):
126 idx = INAT_SEG_REG_GS;
129 /* No default action needed. */
133 /* More than one segment override prefix leads to undefined behavior. */
134 if (num_overrides > 1)
141 * check_seg_overrides() - check if segment override prefixes are allowed
142 * @insn: Valid instruction with segment override prefixes
143 * @regoff: Operand offset, in pt_regs, for which the check is performed
145 * For a particular register used in register-indirect addressing, determine if
146 * segment override prefixes can be used. Specifically, no overrides are allowed
147 * for rDI if used with a string instruction.
151 * True if segment override prefixes can be used with the register indicated
152 * in @regoff. False if otherwise.
154 static bool check_seg_overrides(struct insn *insn, int regoff)
156 if (regoff == offsetof(struct pt_regs, di) && is_string_insn(insn))
163 * resolve_default_seg() - resolve default segment register index for an operand
164 * @insn: Instruction with opcode and address size. Must be valid.
165 * @regs: Register values as seen when entering kernel mode
166 * @off: Operand offset, in pt_regs, for which resolution is needed
168 * Resolve the default segment register index associated with the instruction
169 * operand register indicated by @off. Such index is resolved based on defaults
170 * described in the Intel Software Development Manual.
174 * If in protected mode, a constant identifying the segment register to use,
175 * among CS, SS, ES or DS. If in long mode, INAT_SEG_REG_IGNORE.
177 * -EINVAL in case of error.
179 static int resolve_default_seg(struct insn *insn, struct pt_regs *regs, int off)
181 if (any_64bit_mode(regs))
182 return INAT_SEG_REG_IGNORE;
184 * Resolve the default segment register as described in Section 3.7.4
185 * of the Intel Software Development Manual Vol. 1:
187 * + DS for all references involving r[ABCD]X, and rSI.
188 * + If used in a string instruction, ES for rDI. Otherwise, DS.
189 * + AX, CX and DX are not valid register operands in 16-bit address
190 * encodings but are valid for 32-bit and 64-bit encodings.
191 * + -EDOM is reserved to identify for cases in which no register
192 * is used (i.e., displacement-only addressing). Use DS.
193 * + SS for rSP or rBP.
198 case offsetof(struct pt_regs, ax):
199 case offsetof(struct pt_regs, cx):
200 case offsetof(struct pt_regs, dx):
201 /* Need insn to verify address size. */
202 if (insn->addr_bytes == 2)
208 case offsetof(struct pt_regs, bx):
209 case offsetof(struct pt_regs, si):
210 return INAT_SEG_REG_DS;
212 case offsetof(struct pt_regs, di):
213 if (is_string_insn(insn))
214 return INAT_SEG_REG_ES;
215 return INAT_SEG_REG_DS;
217 case offsetof(struct pt_regs, bp):
218 case offsetof(struct pt_regs, sp):
219 return INAT_SEG_REG_SS;
221 case offsetof(struct pt_regs, ip):
222 return INAT_SEG_REG_CS;
230 * resolve_seg_reg() - obtain segment register index
231 * @insn: Instruction with operands
232 * @regs: Register values as seen when entering kernel mode
233 * @regoff: Operand offset, in pt_regs, used to determine segment register
235 * Determine the segment register associated with the operands and, if
236 * applicable, prefixes and the instruction pointed by @insn.
238 * The segment register associated to an operand used in register-indirect
239 * addressing depends on:
241 * a) Whether running in long mode (in such a case segments are ignored, except
242 * if FS or GS are used).
244 * b) Whether segment override prefixes can be used. Certain instructions and
245 * registers do not allow override prefixes.
247 * c) Whether segment overrides prefixes are found in the instruction prefixes.
249 * d) If there are not segment override prefixes or they cannot be used, the
250 * default segment register associated with the operand register is used.
252 * The function checks first if segment override prefixes can be used with the
253 * operand indicated by @regoff. If allowed, obtain such overridden segment
254 * register index. Lastly, if not prefixes were found or cannot be used, resolve
255 * the segment register index to use based on the defaults described in the
256 * Intel documentation. In long mode, all segment register indexes will be
257 * ignored, except if overrides were found for FS or GS. All these operations
258 * are done using helper functions.
260 * The operand register, @regoff, is represented as the offset from the base of
263 * As stated, the main use of this function is to determine the segment register
264 * index based on the instruction, its operands and prefixes. Hence, @insn
265 * must be valid. However, if @regoff indicates rIP, we don't need to inspect
266 * @insn at all as in this case CS is used in all cases. This case is checked
267 * before proceeding further.
269 * Please note that this function does not return the value in the segment
270 * register (i.e., the segment selector) but our defined index. The segment
271 * selector needs to be obtained using get_segment_selector() and passing the
272 * segment register index resolved by this function.
276 * An index identifying the segment register to use, among CS, SS, DS,
277 * ES, FS, or GS. INAT_SEG_REG_IGNORE is returned if running in long mode.
279 * -EINVAL in case of error.
281 static int resolve_seg_reg(struct insn *insn, struct pt_regs *regs, int regoff)
286 * In the unlikely event of having to resolve the segment register
287 * index for rIP, do it first. Segment override prefixes should not
288 * be used. Hence, it is not necessary to inspect the instruction,
289 * which may be invalid at this point.
291 if (regoff == offsetof(struct pt_regs, ip)) {
292 if (any_64bit_mode(regs))
293 return INAT_SEG_REG_IGNORE;
295 return INAT_SEG_REG_CS;
301 if (!check_seg_overrides(insn, regoff))
302 return resolve_default_seg(insn, regs, regoff);
304 idx = get_seg_reg_override_idx(insn);
308 if (idx == INAT_SEG_REG_DEFAULT)
309 return resolve_default_seg(insn, regs, regoff);
312 * In long mode, segment override prefixes are ignored, except for
313 * overrides for FS and GS.
315 if (any_64bit_mode(regs)) {
316 if (idx != INAT_SEG_REG_FS &&
317 idx != INAT_SEG_REG_GS)
318 idx = INAT_SEG_REG_IGNORE;
325 * get_segment_selector() - obtain segment selector
326 * @regs: Register values as seen when entering kernel mode
327 * @seg_reg_idx: Segment register index to use
329 * Obtain the segment selector from any of the CS, SS, DS, ES, FS, GS segment
330 * registers. In CONFIG_X86_32, the segment is obtained from either pt_regs or
331 * kernel_vm86_regs as applicable. In CONFIG_X86_64, CS and SS are obtained
332 * from pt_regs. DS, ES, FS and GS are obtained by reading the actual CPU
333 * registers. This done for only for completeness as in CONFIG_X86_64 segment
334 * registers are ignored.
338 * Value of the segment selector, including null when running in
343 static short get_segment_selector(struct pt_regs *regs, int seg_reg_idx)
348 switch (seg_reg_idx) {
349 case INAT_SEG_REG_IGNORE:
351 case INAT_SEG_REG_CS:
352 return (unsigned short)(regs->cs & 0xffff);
353 case INAT_SEG_REG_SS:
354 return (unsigned short)(regs->ss & 0xffff);
355 case INAT_SEG_REG_DS:
356 savesegment(ds, sel);
358 case INAT_SEG_REG_ES:
359 savesegment(es, sel);
361 case INAT_SEG_REG_FS:
362 savesegment(fs, sel);
364 case INAT_SEG_REG_GS:
365 savesegment(gs, sel);
370 #else /* CONFIG_X86_32 */
371 struct kernel_vm86_regs *vm86regs = (struct kernel_vm86_regs *)regs;
373 if (v8086_mode(regs)) {
374 switch (seg_reg_idx) {
375 case INAT_SEG_REG_CS:
376 return (unsigned short)(regs->cs & 0xffff);
377 case INAT_SEG_REG_SS:
378 return (unsigned short)(regs->ss & 0xffff);
379 case INAT_SEG_REG_DS:
381 case INAT_SEG_REG_ES:
383 case INAT_SEG_REG_FS:
385 case INAT_SEG_REG_GS:
387 case INAT_SEG_REG_IGNORE:
393 switch (seg_reg_idx) {
394 case INAT_SEG_REG_CS:
395 return (unsigned short)(regs->cs & 0xffff);
396 case INAT_SEG_REG_SS:
397 return (unsigned short)(regs->ss & 0xffff);
398 case INAT_SEG_REG_DS:
399 return (unsigned short)(regs->ds & 0xffff);
400 case INAT_SEG_REG_ES:
401 return (unsigned short)(regs->es & 0xffff);
402 case INAT_SEG_REG_FS:
403 return (unsigned short)(regs->fs & 0xffff);
404 case INAT_SEG_REG_GS:
405 return get_user_gs(regs);
406 case INAT_SEG_REG_IGNORE:
410 #endif /* CONFIG_X86_64 */
413 static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
418 static const int regoff[] = {
419 offsetof(struct pt_regs, ax),
420 offsetof(struct pt_regs, cx),
421 offsetof(struct pt_regs, dx),
422 offsetof(struct pt_regs, bx),
423 offsetof(struct pt_regs, sp),
424 offsetof(struct pt_regs, bp),
425 offsetof(struct pt_regs, si),
426 offsetof(struct pt_regs, di),
428 offsetof(struct pt_regs, r8),
429 offsetof(struct pt_regs, r9),
430 offsetof(struct pt_regs, r10),
431 offsetof(struct pt_regs, r11),
432 offsetof(struct pt_regs, r12),
433 offsetof(struct pt_regs, r13),
434 offsetof(struct pt_regs, r14),
435 offsetof(struct pt_regs, r15),
438 int nr_registers = ARRAY_SIZE(regoff);
440 * Don't possibly decode a 32-bit instructions as
441 * reading a 64-bit-only register.
443 if (IS_ENABLED(CONFIG_X86_64) && !insn->x86_64)
448 regno = X86_MODRM_RM(insn->modrm.value);
451 * ModRM.mod == 0 and ModRM.rm == 5 means a 32-bit displacement
452 * follows the ModRM byte.
454 if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5)
457 if (X86_REX_B(insn->rex_prefix.value))
462 regno = X86_MODRM_REG(insn->modrm.value);
464 if (X86_REX_R(insn->rex_prefix.value))
469 regno = X86_SIB_INDEX(insn->sib.value);
470 if (X86_REX_X(insn->rex_prefix.value))
474 * If ModRM.mod != 3 and SIB.index = 4 the scale*index
475 * portion of the address computation is null. This is
476 * true only if REX.X is 0. In such a case, the SIB index
477 * is used in the address computation.
479 if (X86_MODRM_MOD(insn->modrm.value) != 3 && regno == 4)
484 regno = X86_SIB_BASE(insn->sib.value);
486 * If ModRM.mod is 0 and SIB.base == 5, the base of the
487 * register-indirect addressing is 0. In this case, a
488 * 32-bit displacement follows the SIB byte.
490 if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5)
493 if (X86_REX_B(insn->rex_prefix.value))
498 pr_err_ratelimited("invalid register type: %d\n", type);
502 if (regno >= nr_registers) {
503 WARN_ONCE(1, "decoded an instruction with an invalid register");
506 return regoff[regno];
510 * get_reg_offset_16() - Obtain offset of register indicated by instruction
511 * @insn: Instruction containing ModRM byte
512 * @regs: Register values as seen when entering kernel mode
513 * @offs1: Offset of the first operand register
514 * @offs2: Offset of the second operand register, if applicable
516 * Obtain the offset, in pt_regs, of the registers indicated by the ModRM byte
517 * in @insn. This function is to be used with 16-bit address encodings. The
518 * @offs1 and @offs2 will be written with the offset of the two registers
519 * indicated by the instruction. In cases where any of the registers is not
520 * referenced by the instruction, the value will be set to -EDOM.
524 * 0 on success, -EINVAL on error.
526 static int get_reg_offset_16(struct insn *insn, struct pt_regs *regs,
527 int *offs1, int *offs2)
530 * 16-bit addressing can use one or two registers. Specifics of
531 * encodings are given in Table 2-1. "16-Bit Addressing Forms with the
532 * ModR/M Byte" of the Intel Software Development Manual.
534 static const int regoff1[] = {
535 offsetof(struct pt_regs, bx),
536 offsetof(struct pt_regs, bx),
537 offsetof(struct pt_regs, bp),
538 offsetof(struct pt_regs, bp),
539 offsetof(struct pt_regs, si),
540 offsetof(struct pt_regs, di),
541 offsetof(struct pt_regs, bp),
542 offsetof(struct pt_regs, bx),
545 static const int regoff2[] = {
546 offsetof(struct pt_regs, si),
547 offsetof(struct pt_regs, di),
548 offsetof(struct pt_regs, si),
549 offsetof(struct pt_regs, di),
556 if (!offs1 || !offs2)
559 /* Operand is a register, use the generic function. */
560 if (X86_MODRM_MOD(insn->modrm.value) == 3) {
561 *offs1 = insn_get_modrm_rm_off(insn, regs);
566 *offs1 = regoff1[X86_MODRM_RM(insn->modrm.value)];
567 *offs2 = regoff2[X86_MODRM_RM(insn->modrm.value)];
570 * If ModRM.mod is 0 and ModRM.rm is 110b, then we use displacement-
571 * only addressing. This means that no registers are involved in
572 * computing the effective address. Thus, ensure that the first
573 * register offset is invalid. The second register offset is already
574 * invalid under the aforementioned conditions.
576 if ((X86_MODRM_MOD(insn->modrm.value) == 0) &&
577 (X86_MODRM_RM(insn->modrm.value) == 6))
584 * get_desc() - Obtain contents of a segment descriptor
585 * @out: Segment descriptor contents on success
586 * @sel: Segment selector
588 * Given a segment selector, obtain a pointer to the segment descriptor.
589 * Both global and local descriptor tables are supported.
593 * True on success, false on failure.
597 static bool get_desc(struct desc_struct *out, unsigned short sel)
599 struct desc_ptr gdt_desc = {0, 0};
600 unsigned long desc_base;
602 #ifdef CONFIG_MODIFY_LDT_SYSCALL
603 if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) {
604 bool success = false;
605 struct ldt_struct *ldt;
607 /* Bits [15:3] contain the index of the desired entry. */
610 mutex_lock(¤t->active_mm->context.lock);
611 ldt = current->active_mm->context.ldt;
612 if (ldt && sel < ldt->nr_entries) {
613 *out = ldt->entries[sel];
617 mutex_unlock(¤t->active_mm->context.lock);
622 native_store_gdt(&gdt_desc);
625 * Segment descriptors have a size of 8 bytes. Thus, the index is
626 * multiplied by 8 to obtain the memory offset of the desired descriptor
627 * from the base of the GDT. As bits [15:3] of the segment selector
628 * contain the index, it can be regarded as multiplied by 8 already.
629 * All that remains is to clear bits [2:0].
631 desc_base = sel & ~(SEGMENT_RPL_MASK | SEGMENT_TI_MASK);
633 if (desc_base > gdt_desc.size)
636 *out = *(struct desc_struct *)(gdt_desc.address + desc_base);
641 * insn_get_seg_base() - Obtain base address of segment descriptor.
642 * @regs: Register values as seen when entering kernel mode
643 * @seg_reg_idx: Index of the segment register pointing to seg descriptor
645 * Obtain the base address of the segment as indicated by the segment descriptor
646 * pointed by the segment selector. The segment selector is obtained from the
647 * input segment register index @seg_reg_idx.
651 * In protected mode, base address of the segment. Zero in long mode,
652 * except when FS or GS are used. In virtual-8086 mode, the segment
653 * selector shifted 4 bits to the right.
655 * -1L in case of error.
657 unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
659 struct desc_struct desc;
662 sel = get_segment_selector(regs, seg_reg_idx);
666 if (v8086_mode(regs))
668 * Base is simply the segment selector shifted 4
671 return (unsigned long)(sel << 4);
673 if (any_64bit_mode(regs)) {
675 * Only FS or GS will have a base address, the rest of
676 * the segments' bases are forced to 0.
680 if (seg_reg_idx == INAT_SEG_REG_FS) {
681 rdmsrl(MSR_FS_BASE, base);
682 } else if (seg_reg_idx == INAT_SEG_REG_GS) {
684 * swapgs was called at the kernel entry point. Thus,
685 * MSR_KERNEL_GS_BASE will have the user-space GS base.
688 rdmsrl(MSR_KERNEL_GS_BASE, base);
690 rdmsrl(MSR_GS_BASE, base);
697 /* In protected mode the segment selector cannot be null. */
701 if (!get_desc(&desc, sel))
704 return get_desc_base(&desc);
708 * get_seg_limit() - Obtain the limit of a segment descriptor
709 * @regs: Register values as seen when entering kernel mode
710 * @seg_reg_idx: Index of the segment register pointing to seg descriptor
712 * Obtain the limit of the segment as indicated by the segment descriptor
713 * pointed by the segment selector. The segment selector is obtained from the
714 * input segment register index @seg_reg_idx.
718 * In protected mode, the limit of the segment descriptor in bytes.
719 * In long mode and virtual-8086 mode, segment limits are not enforced. Thus,
720 * limit is returned as -1L to imply a limit-less segment.
722 * Zero is returned on error.
724 static unsigned long get_seg_limit(struct pt_regs *regs, int seg_reg_idx)
726 struct desc_struct desc;
730 sel = get_segment_selector(regs, seg_reg_idx);
734 if (any_64bit_mode(regs) || v8086_mode(regs))
740 if (!get_desc(&desc, sel))
744 * If the granularity bit is set, the limit is given in multiples
745 * of 4096. This also means that the 12 least significant bits are
746 * not tested when checking the segment limits. In practice,
747 * this means that the segment ends in (limit << 12) + 0xfff.
749 limit = get_desc_limit(&desc);
751 limit = (limit << 12) + 0xfff;
757 * insn_get_code_seg_params() - Obtain code segment parameters
758 * @regs: Structure with register values as seen when entering kernel mode
760 * Obtain address and operand sizes of the code segment. It is obtained from the
761 * selector contained in the CS register in regs. In protected mode, the default
762 * address is determined by inspecting the L and D bits of the segment
763 * descriptor. In virtual-8086 mode, the default is always two bytes for both
764 * address and operand sizes.
768 * An int containing ORed-in default parameters on success.
772 int insn_get_code_seg_params(struct pt_regs *regs)
774 struct desc_struct desc;
777 if (v8086_mode(regs))
778 /* Address and operand size are both 16-bit. */
779 return INSN_CODE_SEG_PARAMS(2, 2);
781 sel = get_segment_selector(regs, INAT_SEG_REG_CS);
785 if (!get_desc(&desc, sel))
789 * The most significant byte of the Type field of the segment descriptor
790 * determines whether a segment contains data or code. If this is a data
791 * segment, return error.
793 if (!(desc.type & BIT(3)))
796 switch ((desc.l << 1) | desc.d) {
798 * Legacy mode. CS.L=0, CS.D=0. Address and operand size are
801 return INSN_CODE_SEG_PARAMS(2, 2);
803 * Legacy mode. CS.L=0, CS.D=1. Address and operand size are
806 return INSN_CODE_SEG_PARAMS(4, 4);
808 * IA-32e 64-bit mode. CS.L=1, CS.D=0. Address size is 64-bit;
809 * operand size is 32-bit.
811 return INSN_CODE_SEG_PARAMS(4, 8);
812 case 3: /* Invalid setting. CS.L=1, CS.D=1 */
820 * insn_get_modrm_rm_off() - Obtain register in r/m part of the ModRM byte
821 * @insn: Instruction containing the ModRM byte
822 * @regs: Register values as seen when entering kernel mode
826 * The register indicated by the r/m part of the ModRM byte. The
827 * register is obtained as an offset from the base of pt_regs. In specific
828 * cases, the returned value can be -EDOM to indicate that the particular value
829 * of ModRM does not refer to a register and shall be ignored.
831 int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs)
833 return get_reg_offset(insn, regs, REG_TYPE_RM);
837 * insn_get_modrm_reg_off() - Obtain register in reg part of the ModRM byte
838 * @insn: Instruction containing the ModRM byte
839 * @regs: Register values as seen when entering kernel mode
843 * The register indicated by the reg part of the ModRM byte. The
844 * register is obtained as an offset from the base of pt_regs.
846 int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs)
848 return get_reg_offset(insn, regs, REG_TYPE_REG);
852 * get_seg_base_limit() - obtain base address and limit of a segment
853 * @insn: Instruction. Must be valid.
854 * @regs: Register values as seen when entering kernel mode
855 * @regoff: Operand offset, in pt_regs, used to resolve segment descriptor
856 * @base: Obtained segment base
857 * @limit: Obtained segment limit
859 * Obtain the base address and limit of the segment associated with the operand
860 * @regoff and, if any or allowed, override prefixes in @insn. This function is
861 * different from insn_get_seg_base() as the latter does not resolve the segment
862 * associated with the instruction operand. If a limit is not needed (e.g.,
863 * when running in long mode), @limit can be NULL.
867 * 0 on success. @base and @limit will contain the base address and of the
868 * resolved segment, respectively.
872 static int get_seg_base_limit(struct insn *insn, struct pt_regs *regs,
873 int regoff, unsigned long *base,
874 unsigned long *limit)
881 seg_reg_idx = resolve_seg_reg(insn, regs, regoff);
885 *base = insn_get_seg_base(regs, seg_reg_idx);
892 *limit = get_seg_limit(regs, seg_reg_idx);
900 * get_eff_addr_reg() - Obtain effective address from register operand
901 * @insn: Instruction. Must be valid.
902 * @regs: Register values as seen when entering kernel mode
903 * @regoff: Obtained operand offset, in pt_regs, with the effective address
904 * @eff_addr: Obtained effective address
906 * Obtain the effective address stored in the register operand as indicated by
907 * the ModRM byte. This function is to be used only with register addressing
908 * (i.e., ModRM.mod is 3). The effective address is saved in @eff_addr. The
909 * register operand, as an offset from the base of pt_regs, is saved in @regoff;
910 * such offset can then be used to resolve the segment associated with the
911 * operand. This function can be used with any of the supported address sizes
916 * 0 on success. @eff_addr will have the effective address stored in the
917 * operand indicated by ModRM. @regoff will have such operand as an offset from
918 * the base of pt_regs.
922 static int get_eff_addr_reg(struct insn *insn, struct pt_regs *regs,
923 int *regoff, long *eff_addr)
927 ret = insn_get_modrm(insn);
931 if (X86_MODRM_MOD(insn->modrm.value) != 3)
934 *regoff = get_reg_offset(insn, regs, REG_TYPE_RM);
938 /* Ignore bytes that are outside the address size. */
939 if (insn->addr_bytes == 2)
940 *eff_addr = regs_get_register(regs, *regoff) & 0xffff;
941 else if (insn->addr_bytes == 4)
942 *eff_addr = regs_get_register(regs, *regoff) & 0xffffffff;
943 else /* 64-bit address */
944 *eff_addr = regs_get_register(regs, *regoff);
950 * get_eff_addr_modrm() - Obtain referenced effective address via ModRM
951 * @insn: Instruction. Must be valid.
952 * @regs: Register values as seen when entering kernel mode
953 * @regoff: Obtained operand offset, in pt_regs, associated with segment
954 * @eff_addr: Obtained effective address
956 * Obtain the effective address referenced by the ModRM byte of @insn. After
957 * identifying the registers involved in the register-indirect memory reference,
958 * its value is obtained from the operands in @regs. The computed address is
959 * stored @eff_addr. Also, the register operand that indicates the associated
960 * segment is stored in @regoff, this parameter can later be used to determine
965 * 0 on success. @eff_addr will have the referenced effective address. @regoff
966 * will have a register, as an offset from the base of pt_regs, that can be used
967 * to resolve the associated segment.
971 static int get_eff_addr_modrm(struct insn *insn, struct pt_regs *regs,
972 int *regoff, long *eff_addr)
977 if (insn->addr_bytes != 8 && insn->addr_bytes != 4)
980 ret = insn_get_modrm(insn);
984 if (X86_MODRM_MOD(insn->modrm.value) > 2)
987 *regoff = get_reg_offset(insn, regs, REG_TYPE_RM);
990 * -EDOM means that we must ignore the address_offset. In such a case,
991 * in 64-bit mode the effective address relative to the rIP of the
992 * following instruction.
994 if (*regoff == -EDOM) {
995 if (any_64bit_mode(regs))
996 tmp = regs->ip + insn->length;
999 } else if (*regoff < 0) {
1002 tmp = regs_get_register(regs, *regoff);
1005 if (insn->addr_bytes == 4) {
1006 int addr32 = (int)(tmp & 0xffffffff) + insn->displacement.value;
1008 *eff_addr = addr32 & 0xffffffff;
1010 *eff_addr = tmp + insn->displacement.value;
1017 * get_eff_addr_modrm_16() - Obtain referenced effective address via ModRM
1018 * @insn: Instruction. Must be valid.
1019 * @regs: Register values as seen when entering kernel mode
1020 * @regoff: Obtained operand offset, in pt_regs, associated with segment
1021 * @eff_addr: Obtained effective address
1023 * Obtain the 16-bit effective address referenced by the ModRM byte of @insn.
1024 * After identifying the registers involved in the register-indirect memory
1025 * reference, its value is obtained from the operands in @regs. The computed
1026 * address is stored @eff_addr. Also, the register operand that indicates
1027 * the associated segment is stored in @regoff, this parameter can later be used
1028 * to determine such segment.
1032 * 0 on success. @eff_addr will have the referenced effective address. @regoff
1033 * will have a register, as an offset from the base of pt_regs, that can be used
1034 * to resolve the associated segment.
1038 static int get_eff_addr_modrm_16(struct insn *insn, struct pt_regs *regs,
1039 int *regoff, short *eff_addr)
1041 int addr_offset1, addr_offset2, ret;
1042 short addr1 = 0, addr2 = 0, displacement;
1044 if (insn->addr_bytes != 2)
1047 insn_get_modrm(insn);
1049 if (!insn->modrm.nbytes)
1052 if (X86_MODRM_MOD(insn->modrm.value) > 2)
1055 ret = get_reg_offset_16(insn, regs, &addr_offset1, &addr_offset2);
1060 * Don't fail on invalid offset values. They might be invalid because
1061 * they cannot be used for this particular value of ModRM. Instead, use
1062 * them in the computation only if they contain a valid value.
1064 if (addr_offset1 != -EDOM)
1065 addr1 = regs_get_register(regs, addr_offset1) & 0xffff;
1067 if (addr_offset2 != -EDOM)
1068 addr2 = regs_get_register(regs, addr_offset2) & 0xffff;
1070 displacement = insn->displacement.value & 0xffff;
1071 *eff_addr = addr1 + addr2 + displacement;
1074 * The first operand register could indicate to use of either SS or DS
1075 * registers to obtain the segment selector. The second operand
1076 * register can only indicate the use of DS. Thus, the first operand
1077 * will be used to obtain the segment selector.
1079 *regoff = addr_offset1;
1085 * get_eff_addr_sib() - Obtain referenced effective address via SIB
1086 * @insn: Instruction. Must be valid.
1087 * @regs: Register values as seen when entering kernel mode
1088 * @regoff: Obtained operand offset, in pt_regs, associated with segment
1089 * @eff_addr: Obtained effective address
1091 * Obtain the effective address referenced by the SIB byte of @insn. After
1092 * identifying the registers involved in the indexed, register-indirect memory
1093 * reference, its value is obtained from the operands in @regs. The computed
1094 * address is stored @eff_addr. Also, the register operand that indicates the
1095 * associated segment is stored in @regoff, this parameter can later be used to
1096 * determine such segment.
1100 * 0 on success. @eff_addr will have the referenced effective address.
1101 * @base_offset will have a register, as an offset from the base of pt_regs,
1102 * that can be used to resolve the associated segment.
1104 * Negative value on error.
1106 static int get_eff_addr_sib(struct insn *insn, struct pt_regs *regs,
1107 int *base_offset, long *eff_addr)
1113 if (insn->addr_bytes != 8 && insn->addr_bytes != 4)
1116 ret = insn_get_modrm(insn);
1120 if (!insn->modrm.nbytes)
1123 if (X86_MODRM_MOD(insn->modrm.value) > 2)
1126 ret = insn_get_sib(insn);
1130 if (!insn->sib.nbytes)
1133 *base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE);
1134 indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX);
1137 * Negative values in the base and index offset means an error when
1138 * decoding the SIB byte. Except -EDOM, which means that the registers
1139 * should not be used in the address computation.
1141 if (*base_offset == -EDOM)
1143 else if (*base_offset < 0)
1146 base = regs_get_register(regs, *base_offset);
1148 if (indx_offset == -EDOM)
1150 else if (indx_offset < 0)
1153 indx = regs_get_register(regs, indx_offset);
1155 if (insn->addr_bytes == 4) {
1156 int addr32, base32, idx32;
1158 base32 = base & 0xffffffff;
1159 idx32 = indx & 0xffffffff;
1161 addr32 = base32 + idx32 * (1 << X86_SIB_SCALE(insn->sib.value));
1162 addr32 += insn->displacement.value;
1164 *eff_addr = addr32 & 0xffffffff;
1166 *eff_addr = base + indx * (1 << X86_SIB_SCALE(insn->sib.value));
1167 *eff_addr += insn->displacement.value;
1174 * get_addr_ref_16() - Obtain the 16-bit address referred by instruction
1175 * @insn: Instruction containing ModRM byte and displacement
1176 * @regs: Register values as seen when entering kernel mode
1178 * This function is to be used with 16-bit address encodings. Obtain the memory
1179 * address referred by the instruction's ModRM and displacement bytes. Also, the
1180 * segment used as base is determined by either any segment override prefixes in
1181 * @insn or the default segment of the registers involved in the address
1182 * computation. In protected mode, segment limits are enforced.
1186 * Linear address referenced by the instruction operands on success.
1190 static void __user *get_addr_ref_16(struct insn *insn, struct pt_regs *regs)
1192 unsigned long linear_addr = -1L, seg_base, seg_limit;
1197 if (insn_get_displacement(insn))
1200 if (insn->addr_bytes != 2)
1203 if (X86_MODRM_MOD(insn->modrm.value) == 3) {
1204 ret = get_eff_addr_reg(insn, regs, ®off, &tmp);
1210 ret = get_eff_addr_modrm_16(insn, regs, ®off, &eff_addr);
1215 ret = get_seg_base_limit(insn, regs, regoff, &seg_base, &seg_limit);
1220 * Before computing the linear address, make sure the effective address
1221 * is within the limits of the segment. In virtual-8086 mode, segment
1222 * limits are not enforced. In such a case, the segment limit is -1L to
1223 * reflect this fact.
1225 if ((unsigned long)(eff_addr & 0xffff) > seg_limit)
1228 linear_addr = (unsigned long)(eff_addr & 0xffff) + seg_base;
1230 /* Limit linear address to 20 bits */
1231 if (v8086_mode(regs))
1232 linear_addr &= 0xfffff;
1235 return (void __user *)linear_addr;
1239 * get_addr_ref_32() - Obtain a 32-bit linear address
1240 * @insn: Instruction with ModRM, SIB bytes and displacement
1241 * @regs: Register values as seen when entering kernel mode
1243 * This function is to be used with 32-bit address encodings to obtain the
1244 * linear memory address referred by the instruction's ModRM, SIB,
1245 * displacement bytes and segment base address, as applicable. If in protected
1246 * mode, segment limits are enforced.
1250 * Linear address referenced by instruction and registers on success.
1254 static void __user *get_addr_ref_32(struct insn *insn, struct pt_regs *regs)
1256 unsigned long linear_addr = -1L, seg_base, seg_limit;
1257 int eff_addr, regoff;
1261 if (insn->addr_bytes != 4)
1264 if (X86_MODRM_MOD(insn->modrm.value) == 3) {
1265 ret = get_eff_addr_reg(insn, regs, ®off, &tmp);
1272 if (insn->sib.nbytes) {
1273 ret = get_eff_addr_sib(insn, regs, ®off, &tmp);
1279 ret = get_eff_addr_modrm(insn, regs, ®off, &tmp);
1287 ret = get_seg_base_limit(insn, regs, regoff, &seg_base, &seg_limit);
1292 * In protected mode, before computing the linear address, make sure
1293 * the effective address is within the limits of the segment.
1294 * 32-bit addresses can be used in long and virtual-8086 modes if an
1295 * address override prefix is used. In such cases, segment limits are
1296 * not enforced. When in virtual-8086 mode, the segment limit is -1L
1297 * to reflect this situation.
1299 * After computed, the effective address is treated as an unsigned
1302 if (!any_64bit_mode(regs) && ((unsigned int)eff_addr > seg_limit))
1306 * Even though 32-bit address encodings are allowed in virtual-8086
1307 * mode, the address range is still limited to [0x-0xffff].
1309 if (v8086_mode(regs) && (eff_addr & ~0xffff))
1313 * Data type long could be 64 bits in size. Ensure that our 32-bit
1314 * effective address is not sign-extended when computing the linear
1317 linear_addr = (unsigned long)(eff_addr & 0xffffffff) + seg_base;
1319 /* Limit linear address to 20 bits */
1320 if (v8086_mode(regs))
1321 linear_addr &= 0xfffff;
1324 return (void __user *)linear_addr;
1328 * get_addr_ref_64() - Obtain a 64-bit linear address
1329 * @insn: Instruction struct with ModRM and SIB bytes and displacement
1330 * @regs: Structure with register values as seen when entering kernel mode
1332 * This function is to be used with 64-bit address encodings to obtain the
1333 * linear memory address referred by the instruction's ModRM, SIB,
1334 * displacement bytes and segment base address, as applicable.
1338 * Linear address referenced by instruction and registers on success.
1342 #ifndef CONFIG_X86_64
1343 static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
1345 return (void __user *)-1L;
1348 static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
1350 unsigned long linear_addr = -1L, seg_base;
1354 if (insn->addr_bytes != 8)
1357 if (X86_MODRM_MOD(insn->modrm.value) == 3) {
1358 ret = get_eff_addr_reg(insn, regs, ®off, &eff_addr);
1363 if (insn->sib.nbytes) {
1364 ret = get_eff_addr_sib(insn, regs, ®off, &eff_addr);
1368 ret = get_eff_addr_modrm(insn, regs, ®off, &eff_addr);
1375 ret = get_seg_base_limit(insn, regs, regoff, &seg_base, NULL);
1379 linear_addr = (unsigned long)eff_addr + seg_base;
1382 return (void __user *)linear_addr;
1384 #endif /* CONFIG_X86_64 */
1387 * insn_get_addr_ref() - Obtain the linear address referred by instruction
1388 * @insn: Instruction structure containing ModRM byte and displacement
1389 * @regs: Structure with register values as seen when entering kernel mode
1391 * Obtain the linear address referred by the instruction's ModRM, SIB and
1392 * displacement bytes, and segment base, as applicable. In protected mode,
1393 * segment limits are enforced.
1397 * Linear address referenced by instruction and registers on success.
1401 void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
1404 return (void __user *)-1L;
1406 if (insn_get_opcode(insn))
1407 return (void __user *)-1L;
1409 switch (insn->addr_bytes) {
1411 return get_addr_ref_16(insn, regs);
1413 return get_addr_ref_32(insn, regs);
1415 return get_addr_ref_64(insn, regs);
1417 return (void __user *)-1L;
1421 int insn_get_effective_ip(struct pt_regs *regs, unsigned long *ip)
1423 unsigned long seg_base = 0;
1426 * If not in user-space long mode, a custom code segment could be in
1427 * use. This is true in protected mode (if the process defined a local
1428 * descriptor table), or virtual-8086 mode. In most of the cases
1429 * seg_base will be zero as in USER_CS.
1431 if (!user_64bit_mode(regs)) {
1432 seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS);
1433 if (seg_base == -1L)
1437 *ip = seg_base + regs->ip;
1443 * insn_fetch_from_user() - Copy instruction bytes from user-space memory
1444 * @regs: Structure with register values as seen when entering kernel mode
1445 * @buf: Array to store the fetched instruction
1447 * Gets the linear address of the instruction and copies the instruction bytes
1452 * - number of instruction bytes copied.
1453 * - 0 if nothing was copied.
1454 * - -EINVAL if the linear address of the instruction could not be calculated
1456 int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE])
1461 if (insn_get_effective_ip(regs, &ip))
1464 not_copied = copy_from_user(buf, (void __user *)ip, MAX_INSN_SIZE);
1466 return MAX_INSN_SIZE - not_copied;
1470 * insn_fetch_from_user_inatomic() - Copy instruction bytes from user-space memory
1471 * while in atomic code
1472 * @regs: Structure with register values as seen when entering kernel mode
1473 * @buf: Array to store the fetched instruction
1475 * Gets the linear address of the instruction and copies the instruction bytes
1476 * to the buf. This function must be used in atomic context.
1480 * - number of instruction bytes copied.
1481 * - 0 if nothing was copied.
1482 * - -EINVAL if the linear address of the instruction could not be calculated.
1484 int insn_fetch_from_user_inatomic(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE])
1489 if (insn_get_effective_ip(regs, &ip))
1492 not_copied = __copy_from_user_inatomic(buf, (void __user *)ip, MAX_INSN_SIZE);
1494 return MAX_INSN_SIZE - not_copied;
1498 * insn_decode_from_regs() - Decode an instruction
1499 * @insn: Structure to store decoded instruction
1500 * @regs: Structure with register values as seen when entering kernel mode
1501 * @buf: Buffer containing the instruction bytes
1502 * @buf_size: Number of instruction bytes available in buf
1504 * Decodes the instruction provided in buf and stores the decoding results in
1505 * insn. Also determines the correct address and operand sizes.
1509 * True if instruction was decoded, False otherwise.
1511 bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs,
1512 unsigned char buf[MAX_INSN_SIZE], int buf_size)
1516 insn_init(insn, buf, buf_size, user_64bit_mode(regs));
1519 * Override the default operand and address sizes with what is specified
1520 * in the code segment descriptor. The instruction decoder only sets
1521 * the address size it to either 4 or 8 address bytes and does nothing
1522 * for the operand bytes. This OK for most of the cases, but we could
1523 * have special cases where, for instance, a 16-bit code segment
1524 * descriptor is used.
1525 * If there is an address override prefix, the instruction decoder
1526 * correctly updates these values, even for 16-bit defaults.
1528 seg_defs = insn_get_code_seg_params(regs);
1529 if (seg_defs == -EINVAL)
1532 insn->addr_bytes = INSN_CODE_SEG_ADDR_SZ(seg_defs);
1533 insn->opnd_bytes = INSN_CODE_SEG_OPND_SZ(seg_defs);
1535 if (insn_get_length(insn))
1538 if (buf_size < insn->length)