LoongArch: Add alternative runtime patching mechanism (19e5eb15) · Commits · EulixOS / Software / Kernel

arch/loongarch/include/asm/alternative-asm.h

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		/* SPDX-License-Identifier: GPL-2.0 */
		#ifndef _ASM_ALTERNATIVE_ASM_H
		#define _ASM_ALTERNATIVE_ASM_H

		#ifdef __ASSEMBLY__

		#include <asm/asm.h>

		/*
		* Issue one struct alt_instr descriptor entry (need to put it into
		* the section .altinstructions, see below). This entry contains
		* enough information for the alternatives patching code to patch an
		* instruction. See apply_alternatives().
		*/
		.macro altinstruction_entry orig alt feature orig_len alt_len
		.long \orig - .
		.long \alt - .
		.short \feature
		.byte \orig_len
		.byte \alt_len
		.endm

		/*
		* Define an alternative between two instructions. If @feature is
		* present, early code in apply_alternatives() replaces @oldinstr with
		* @newinstr. ".fill" directive takes care of proper instruction padding
		* in case @newinstr is longer than @oldinstr.
		*/
		.macro ALTERNATIVE oldinstr, newinstr, feature
		140 :
		\oldinstr
		141 :
		.fill - (((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)) / 4, 4, 0x03400000
		142 :

		.pushsection .altinstructions, "a"
		altinstruction_entry 140b, 143f, \feature, 142b-140b, 144f-143f
		.popsection

		.subsection 1
		143 :
		\newinstr
		144 :
		.previous
		.endm

		#define old_len (141b-140b)
		#define new_len1 (144f-143f)
		#define new_len2 (145f-144f)

		#define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))

		/*
		* Same as ALTERNATIVE macro above but for two alternatives. If CPU
		* has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
		* @feature2, it replaces @oldinstr with @feature2.
		*/
		.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
		140 :
		\oldinstr
		141 :
		.fill - ((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
		(alt_max_short(new_len1, new_len2) - (old_len)) / 4, 4, 0x03400000
		142 :

		.pushsection .altinstructions, "a"
		altinstruction_entry 140b, 143f, \feature1, 142b-140b, 144f-143f, 142b-141b
		altinstruction_entry 140b, 144f, \feature2, 142b-140b, 145f-144f, 142b-141b
		.popsection

		.subsection 1
		143 :
		\newinstr1
		144 :
		\newinstr2
		145 :
		.previous
		.endm

		#endif /* __ASSEMBLY__ */

		#endif /* _ASM_ALTERNATIVE_ASM_H */

arch/loongarch/include/asm/alternative.h

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		/* SPDX-License-Identifier: GPL-2.0 */
		#ifndef _ASM_ALTERNATIVE_H
		#define _ASM_ALTERNATIVE_H

		#ifndef __ASSEMBLY__

		#include <linux/types.h>
		#include <linux/stddef.h>
		#include <linux/stringify.h>
		#include <asm/asm.h>

		struct alt_instr {
		s32 instr_offset; /* offset to original instruction */
		s32 replace_offset; /* offset to replacement instruction */
		u16 feature; /* feature bit set for replacement */
		u8 instrlen; /* length of original instruction */
		u8 replacementlen; /* length of new instruction */
		} __packed;

		/*
		* Debug flag that can be tested to see whether alternative
		* instructions were patched in already:
		*/
		extern int alternatives_patched;
		extern struct alt_instr __alt_instructions[], __alt_instructions_end[];

		extern void alternative_instructions(void);
		extern void apply_alternatives(struct alt_instr start, struct alt_instr end);

		#define b_replacement(num) "664"#num
		#define e_replacement(num) "665"#num

		#define alt_end_marker "663"
		#define alt_slen "662b-661b"
		#define alt_total_slen alt_end_marker"b-661b"
		#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"

		#define __OLDINSTR(oldinstr, num) \
		"661:\n\t" oldinstr "\n662:\n" \
		".fill -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
		"((" alt_rlen(num) ")-(" alt_slen ")) / 4, 4, 0x03400000\n"

		#define OLDINSTR(oldinstr, num) \
		__OLDINSTR(oldinstr, num) \
		alt_end_marker ":\n"

		#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"

		/*
		* Pad the second replacement alternative with additional NOPs if it is
		* additionally longer than the first replacement alternative.
		*/
		#define OLDINSTR_2(oldinstr, num1, num2) \
		"661:\n\t" oldinstr "\n662:\n" \
		".fill -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
		"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) / 4, " \
		"4, 0x03400000\n" \
		alt_end_marker ":\n"

		#define ALTINSTR_ENTRY(feature, num) \
		" .long 661b - .\n" /* label */ \
		" .long " b_replacement(num)"f - .\n" /* new instruction */ \
		" .short " __stringify(feature) "\n" /* feature bit */ \
		" .byte " alt_total_slen "\n" /* source len */ \
		" .byte " alt_rlen(num) "\n" /* replacement len */

		#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
		b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"

		/* alternative assembly primitive: */
		#define ALTERNATIVE(oldinstr, newinstr, feature) \
		OLDINSTR(oldinstr, 1) \
		".pushsection .altinstructions,\"a\"\n" \
		ALTINSTR_ENTRY(feature, 1) \
		".popsection\n" \
		".subsection 1\n" \
		ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
		".previous\n"

		#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
		OLDINSTR_2(oldinstr, 1, 2) \
		".pushsection .altinstructions,\"a\"\n" \
		ALTINSTR_ENTRY(feature1, 1) \
		ALTINSTR_ENTRY(feature2, 2) \
		".popsection\n" \
		".subsection 1\n" \
		ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
		ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
		".previous\n"

		/*
		* Alternative instructions for different CPU types or capabilities.
		*
		* This allows to use optimized instructions even on generic binary
		* kernels.
		*
		* length of oldinstr must be longer or equal the length of newinstr
		* It can be padded with nops as needed.
		*
		* For non barrier like inlines please define new variants
		* without volatile and memory clobber.
		*/
		#define alternative(oldinstr, newinstr, feature) \
		(asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory"))

		#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
		(asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory"))

		#endif /* __ASSEMBLY__ */

		#endif /* _ASM_ALTERNATIVE_H */

arch/loongarch/include/asm/bugs.h

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		/* SPDX-License-Identifier: GPL-2.0 */
		/*
		* This is included by init/main.c to check for architecture-dependent bugs.
		*
		* Copyright (C) 2020-2022 Loongson Technology Corporation Limited
		*/
		#ifndef _ASM_BUGS_H
		#define _ASM_BUGS_H

		#include <asm/cpu.h>
		#include <asm/cpu-info.h>

		extern void check_bugs(void);

		#endif /* _ASM_BUGS_H */

arch/loongarch/include/asm/inst.h

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		@@ -8,6 +8,7 @@
		#include <linux/types.h>
		#include <asm/asm.h>

		#define INSN_NOP 0x03400000
		#define INSN_BREAK 0x002a0000

		#define ADDR_IMMMASK_LU52ID 0xFFF0000000000000
		@@ -28,6 +29,7 @@ enum reg0i26_op {
		enum reg1i20_op {
		lu12iw_op = 0x0a,
		lu32id_op = 0x0b,
		pcaddi_op = 0x0c,
		pcaddu12i_op = 0x0e,
		pcaddu18i_op = 0x0f,
		};
		@@ -35,6 +37,8 @@ enum reg1i20_op {
		enum reg1i21_op {
		beqz_op = 0x10,
		bnez_op = 0x11,
		bceqz_op = 0x12, /* bits[9:8] = 0x00 */
		bcnez_op = 0x12, /* bits[9:8] = 0x01 */
		};

		enum reg2_op {
		@@ -315,6 +319,12 @@ static inline bool is_imm_negative(unsigned long val, unsigned int bit)
		return val & (1UL << (bit - 1));
		}

		static inline bool is_pc_ins(union loongarch_instruction *ip)
		{
		return ip->reg1i20_format.opcode >= pcaddi_op &&
		ip->reg1i20_format.opcode <= pcaddu18i_op;
		}

		static inline bool is_branch_ins(union loongarch_instruction *ip)
		{
		return ip->reg1i21_format.opcode >= beqz_op &&
		@@ -353,6 +363,14 @@ static inline bool unsigned_imm_check(unsigned long val, unsigned int bit)
		return val < (1UL << bit);
		}

		static inline unsigned long sign_extend(unsigned long val, unsigned int idx)
		{
		if (!is_imm_negative(val, idx + 1))
		return ((1UL << idx) - 1) & val;
		else
		return ~((1UL << idx) - 1) \| val;
		}

		#define DEF_EMIT_REG0I26_FORMAT(NAME, OP) \
		static inline void emit_##NAME(union loongarch_instruction *insn, \
		int offset) \

arch/loongarch/kernel/Makefile

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		@@ -8,7 +8,7 @@ extra-y := vmlinux.lds
		obj-y += head.o cpu-probe.o cacheinfo.o env.o setup.o entry.o genex.o \
		traps.o irq.o idle.o process.o dma.o mem.o io.o reset.o switch.o \
		elf.o syscall.o signal.o time.o topology.o inst.o ptrace.o vdso.o \
		unaligned.o
		alternative.o unaligned.o

		obj-$(CONFIG_ACPI) += acpi.o
		obj-$(CONFIG_EFI) += efi.o