xref: /openbmc/linux/arch/x86/include/asm/text-patching.h (revision 18cbc8bed0c70795d2064217c89894e28eafdf04)
1b2441318SGreg Kroah-Hartman /* SPDX-License-Identifier: GPL-2.0 */
235de5b06SAndy Lutomirski #ifndef _ASM_X86_TEXT_PATCHING_H
335de5b06SAndy Lutomirski #define _ASM_X86_TEXT_PATCHING_H
435de5b06SAndy Lutomirski 
535de5b06SAndy Lutomirski #include <linux/types.h>
635de5b06SAndy Lutomirski #include <linux/stddef.h>
735de5b06SAndy Lutomirski #include <asm/ptrace.h>
835de5b06SAndy Lutomirski 
935de5b06SAndy Lutomirski struct paravirt_patch_site;
1035de5b06SAndy Lutomirski #ifdef CONFIG_PARAVIRT
1135de5b06SAndy Lutomirski void apply_paravirt(struct paravirt_patch_site *start,
1235de5b06SAndy Lutomirski 		    struct paravirt_patch_site *end);
1335de5b06SAndy Lutomirski #else
1435de5b06SAndy Lutomirski static inline void apply_paravirt(struct paravirt_patch_site *start,
1535de5b06SAndy Lutomirski 				  struct paravirt_patch_site *end)
1635de5b06SAndy Lutomirski {}
1735de5b06SAndy Lutomirski #define __parainstructions	NULL
1835de5b06SAndy Lutomirski #define __parainstructions_end	NULL
1935de5b06SAndy Lutomirski #endif
2035de5b06SAndy Lutomirski 
21c0213b0aSDaniel Bristot de Oliveira /*
22c0213b0aSDaniel Bristot de Oliveira  * Currently, the max observed size in the kernel code is
23c0213b0aSDaniel Bristot de Oliveira  * JUMP_LABEL_NOP_SIZE/RELATIVEJUMP_SIZE, which are 5.
24c0213b0aSDaniel Bristot de Oliveira  * Raise it if needed.
25c0213b0aSDaniel Bristot de Oliveira  */
26c0213b0aSDaniel Bristot de Oliveira #define POKE_MAX_OPCODE_SIZE	5
27c0213b0aSDaniel Bristot de Oliveira 
280a203df5SNadav Amit extern void text_poke_early(void *addr, const void *opcode, size_t len);
2935de5b06SAndy Lutomirski 
3035de5b06SAndy Lutomirski /*
3135de5b06SAndy Lutomirski  * Clear and restore the kernel write-protection flag on the local CPU.
3235de5b06SAndy Lutomirski  * Allows the kernel to edit read-only pages.
3335de5b06SAndy Lutomirski  * Side-effect: any interrupt handler running between save and restore will have
3435de5b06SAndy Lutomirski  * the ability to write to read-only pages.
3535de5b06SAndy Lutomirski  *
3635de5b06SAndy Lutomirski  * Warning:
3735de5b06SAndy Lutomirski  * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
3835de5b06SAndy Lutomirski  * no thread can be preempted in the instructions being modified (no iret to an
3935de5b06SAndy Lutomirski  * invalid instruction possible) or if the instructions are changed from a
4035de5b06SAndy Lutomirski  * consistent state to another consistent state atomically.
4132b1cbe3SMarco Ammon  * On the local CPU you need to be protected against NMI or MCE handlers seeing
4232b1cbe3SMarco Ammon  * an inconsistent instruction while you patch.
4335de5b06SAndy Lutomirski  */
4435de5b06SAndy Lutomirski extern void *text_poke(void *addr, const void *opcode, size_t len);
45e836673cSNadav Amit extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len);
4635de5b06SAndy Lutomirski extern int poke_int3_handler(struct pt_regs *regs);
47c3d6324fSPeter Zijlstra extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate);
48*18cbc8beSPeter Zijlstra 
49*18cbc8beSPeter Zijlstra extern void text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate);
50*18cbc8beSPeter Zijlstra extern void text_poke_finish(void);
51*18cbc8beSPeter Zijlstra 
526fffacb3SPavel Tatashin extern int after_bootmem;
534fc19708SNadav Amit extern __ro_after_init struct mm_struct *poking_mm;
544fc19708SNadav Amit extern __ro_after_init unsigned long poking_addr;
5535de5b06SAndy Lutomirski 
56693713cbSSteven Rostedt (VMware) #ifndef CONFIG_UML_X86
574b33dadfSPeter Zijlstra static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
584b33dadfSPeter Zijlstra {
594b33dadfSPeter Zijlstra 	regs->ip = ip;
604b33dadfSPeter Zijlstra }
614b33dadfSPeter Zijlstra 
624b33dadfSPeter Zijlstra #define INT3_INSN_SIZE		1
63c3d6324fSPeter Zijlstra #define INT3_INSN_OPCODE	0xCC
64c3d6324fSPeter Zijlstra 
654b33dadfSPeter Zijlstra #define CALL_INSN_SIZE		5
66c3d6324fSPeter Zijlstra #define CALL_INSN_OPCODE	0xE8
67c3d6324fSPeter Zijlstra 
68c3d6324fSPeter Zijlstra #define JMP32_INSN_SIZE		5
69c3d6324fSPeter Zijlstra #define JMP32_INSN_OPCODE	0xE9
70c3d6324fSPeter Zijlstra 
71c3d6324fSPeter Zijlstra #define JMP8_INSN_SIZE		2
72c3d6324fSPeter Zijlstra #define JMP8_INSN_OPCODE	0xEB
734b33dadfSPeter Zijlstra 
744b33dadfSPeter Zijlstra static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
754b33dadfSPeter Zijlstra {
764b33dadfSPeter Zijlstra 	/*
774b33dadfSPeter Zijlstra 	 * The int3 handler in entry_64.S adds a gap between the
784b33dadfSPeter Zijlstra 	 * stack where the break point happened, and the saving of
794b33dadfSPeter Zijlstra 	 * pt_regs. We can extend the original stack because of
804b33dadfSPeter Zijlstra 	 * this gap. See the idtentry macro's create_gap option.
818f4a4160SPeter Zijlstra 	 *
828f4a4160SPeter Zijlstra 	 * Similarly entry_32.S will have a gap on the stack for (any) hardware
838f4a4160SPeter Zijlstra 	 * exception and pt_regs; see FIXUP_FRAME.
844b33dadfSPeter Zijlstra 	 */
854b33dadfSPeter Zijlstra 	regs->sp -= sizeof(unsigned long);
864b33dadfSPeter Zijlstra 	*(unsigned long *)regs->sp = val;
874b33dadfSPeter Zijlstra }
884b33dadfSPeter Zijlstra 
894b33dadfSPeter Zijlstra static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func)
904b33dadfSPeter Zijlstra {
914b33dadfSPeter Zijlstra 	int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
924b33dadfSPeter Zijlstra 	int3_emulate_jmp(regs, func);
934b33dadfSPeter Zijlstra }
94693713cbSSteven Rostedt (VMware) #endif /* !CONFIG_UML_X86 */
954b33dadfSPeter Zijlstra 
9635de5b06SAndy Lutomirski #endif /* _ASM_X86_TEXT_PATCHING_H */
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