LoongArch: Add ELF and module support

Add ELF-related definition and module relocation code for basic
LoongArch support.

Cc: Jessica Yu <[e-mail]>
Reviewed-by: WANG Xuerui <[e-mail]>
Reviewed-by: Luis Chamberlain <[e-mail]>
Reviewed-by: Jiaxun Yang <[e-mail]>
Signed-off-by: Huacai Chen <[e-mail]>

arch/loongarch/include/asm/cpufeature.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * CPU feature definitions for module loading, used by
+ * module_cpu_feature_match(), see uapi/asm/hwcap.h for LoongArch CPU features.
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#ifndef __ASM_CPUFEATURE_H
+#define __ASM_CPUFEATURE_H
+
+#include <uapi/asm/hwcap.h>
+#include <asm/elf.h>
+
+#define MAX_CPU_FEATURES (8 * sizeof(elf_hwcap))
+
+#define cpu_feature(x)		ilog2(HWCAP_ ## x)
+
+static inline bool cpu_have_feature(unsigned int num)
+{
+	return elf_hwcap & (1UL << num);
+}
+
+#endif /* __ASM_CPUFEATURE_H */

arch/loongarch/include/asm/elf.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef _ASM_ELF_H
+#define _ASM_ELF_H
+
+#include <linux/auxvec.h>
+#include <linux/fs.h>
+#include <uapi/linux/elf.h>
+
+#include <asm/current.h>
+#include <asm/vdso.h>
+
+/* The ABI of a file. */
+#define EF_LOONGARCH_ABI_LP64_SOFT_FLOAT	0x1
+#define EF_LOONGARCH_ABI_LP64_SINGLE_FLOAT	0x2
+#define EF_LOONGARCH_ABI_LP64_DOUBLE_FLOAT	0x3
+
+#define EF_LOONGARCH_ABI_ILP32_SOFT_FLOAT	0x5
+#define EF_LOONGARCH_ABI_ILP32_SINGLE_FLOAT	0x6
+#define EF_LOONGARCH_ABI_ILP32_DOUBLE_FLOAT	0x7
+
+/* LoongArch relocation types used by the dynamic linker */
+#define R_LARCH_NONE				0
+#define R_LARCH_32				1
+#define R_LARCH_64				2
+#define R_LARCH_RELATIVE			3
+#define R_LARCH_COPY				4
+#define R_LARCH_JUMP_SLOT			5
+#define R_LARCH_TLS_DTPMOD32			6
+#define R_LARCH_TLS_DTPMOD64			7
+#define R_LARCH_TLS_DTPREL32			8
+#define R_LARCH_TLS_DTPREL64			9
+#define R_LARCH_TLS_TPREL32			10
+#define R_LARCH_TLS_TPREL64			11
+#define R_LARCH_IRELATIVE			12
+#define R_LARCH_MARK_LA				20
+#define R_LARCH_MARK_PCREL			21
+#define R_LARCH_SOP_PUSH_PCREL			22
+#define R_LARCH_SOP_PUSH_ABSOLUTE		23
+#define R_LARCH_SOP_PUSH_DUP			24
+#define R_LARCH_SOP_PUSH_GPREL			25
+#define R_LARCH_SOP_PUSH_TLS_TPREL		26
+#define R_LARCH_SOP_PUSH_TLS_GOT		27
+#define R_LARCH_SOP_PUSH_TLS_GD			28
+#define R_LARCH_SOP_PUSH_PLT_PCREL		29
+#define R_LARCH_SOP_ASSERT			30
+#define R_LARCH_SOP_NOT				31
+#define R_LARCH_SOP_SUB				32
+#define R_LARCH_SOP_SL				33
+#define R_LARCH_SOP_SR				34
+#define R_LARCH_SOP_ADD				35
+#define R_LARCH_SOP_AND				36
+#define R_LARCH_SOP_IF_ELSE			37
+#define R_LARCH_SOP_POP_32_S_10_5		38
+#define R_LARCH_SOP_POP_32_U_10_12		39
+#define R_LARCH_SOP_POP_32_S_10_12		40
+#define R_LARCH_SOP_POP_32_S_10_16		41
+#define R_LARCH_SOP_POP_32_S_10_16_S2		42
+#define R_LARCH_SOP_POP_32_S_5_20		43
+#define R_LARCH_SOP_POP_32_S_0_5_10_16_S2	44
+#define R_LARCH_SOP_POP_32_S_0_10_10_16_S2	45
+#define R_LARCH_SOP_POP_32_U			46
+#define R_LARCH_ADD8				47
+#define R_LARCH_ADD16				48
+#define R_LARCH_ADD24				49
+#define R_LARCH_ADD32				50
+#define R_LARCH_ADD64				51
+#define R_LARCH_SUB8				52
+#define R_LARCH_SUB16				53
+#define R_LARCH_SUB24				54
+#define R_LARCH_SUB32				55
+#define R_LARCH_SUB64				56
+#define R_LARCH_GNU_VTINHERIT			57
+#define R_LARCH_GNU_VTENTRY			58
+
+#ifndef ELF_ARCH
+
+/* ELF register definitions */
+
+/*
+ * General purpose have the following registers:
+ *	Register	Number
+ *	GPRs		32
+ *	ORIG_A0		1
+ *	ERA		1
+ *	BADVADDR	1
+ *	CRMD		1
+ *	PRMD		1
+ *	EUEN		1
+ *	ECFG		1
+ *	ESTAT		1
+ *	Reserved	5
+ */
+#define ELF_NGREG	45
+
+/*
+ * Floating point have the following registers:
+ *	Register	Number
+ *	FPR		32
+ *	FCC		1
+ *	FCSR		1
+ */
+#define ELF_NFPREG	34
+
+typedef unsigned long elf_greg_t;
+typedef elf_greg_t elf_gregset_t[ELF_NGREG];
+
+typedef double elf_fpreg_t;
+typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG];
+
+void loongarch_dump_regs64(u64 *uregs, const struct pt_regs *regs);
+
+#ifdef CONFIG_32BIT
+/*
+ * This is used to ensure we don't load something for the wrong architecture.
+ */
+#define elf_check_arch elf32_check_arch
+
+/*
+ * These are used to set parameters in the core dumps.
+ */
+#define ELF_CLASS	ELFCLASS32
+
+#define ELF_CORE_COPY_REGS(dest, regs) \
+	loongarch_dump_regs32((u32 *)&(dest), (regs));
+
+#endif /* CONFIG_32BIT */
+
+#ifdef CONFIG_64BIT
+/*
+ * This is used to ensure we don't load something for the wrong architecture.
+ */
+#define elf_check_arch elf64_check_arch
+
+/*
+ * These are used to set parameters in the core dumps.
+ */
+#define ELF_CLASS	ELFCLASS64
+
+#define ELF_CORE_COPY_REGS(dest, regs) \
+	loongarch_dump_regs64((u64 *)&(dest), (regs));
+
+#endif /* CONFIG_64BIT */
+
+/*
+ * These are used to set parameters in the core dumps.
+ */
+#define ELF_DATA	ELFDATA2LSB
+#define ELF_ARCH	EM_LOONGARCH
+
+#endif /* !defined(ELF_ARCH) */
+
+#define loongarch_elf_check_machine(x) ((x)->e_machine == EM_LOONGARCH)
+
+#define vmcore_elf32_check_arch loongarch_elf_check_machine
+#define vmcore_elf64_check_arch loongarch_elf_check_machine
+
+/*
+ * Return non-zero if HDR identifies an 32bit ELF binary.
+ */
+#define elf32_check_arch(hdr)						\
+({									\
+	int __res = 1;							\
+	struct elfhdr *__h = (hdr);					\
+									\
+	if (!loongarch_elf_check_machine(__h))				\
+		__res = 0;						\
+	if (__h->e_ident[EI_CLASS] != ELFCLASS32)			\
+		__res = 0;						\
+									\
+	__res;								\
+})
+
+/*
+ * Return non-zero if HDR identifies an 64bit ELF binary.
+ */
+#define elf64_check_arch(hdr)						\
+({									\
+	int __res = 1;							\
+	struct elfhdr *__h = (hdr);					\
+									\
+	if (!loongarch_elf_check_machine(__h))				\
+		__res = 0;						\
+	if (__h->e_ident[EI_CLASS] != ELFCLASS64)			\
+		__res = 0;						\
+									\
+	__res;								\
+})
+
+#ifdef CONFIG_32BIT
+
+#define SET_PERSONALITY2(ex, state)					\
+do {									\
+	current->thread.vdso = &vdso_info;				\
+									\
+	loongarch_set_personality_fcsr(state);				\
+									\
+	if (personality(current->personality) != PER_LINUX)		\
+		set_personality(PER_LINUX);				\
+} while (0)
+
+#endif /* CONFIG_32BIT */
+
+#ifdef CONFIG_64BIT
+
+#define SET_PERSONALITY2(ex, state)					\
+do {									\
+	unsigned int p;							\
+									\
+	clear_thread_flag(TIF_32BIT_REGS);				\
+	clear_thread_flag(TIF_32BIT_ADDR);				\
+									\
+	current->thread.vdso = &vdso_info;				\
+	loongarch_set_personality_fcsr(state);				\
+									\
+	p = personality(current->personality);				\
+	if (p != PER_LINUX32 && p != PER_LINUX)				\
+		set_personality(PER_LINUX);				\
+} while (0)
+
+#endif /* CONFIG_64BIT */
+
+#define CORE_DUMP_USE_REGSET
+#define ELF_EXEC_PAGESIZE	PAGE_SIZE
+
+/*
+ * This yields a mask that user programs can use to figure out what
+ * instruction set this cpu supports. This could be done in userspace,
+ * but it's not easy, and we've already done it here.
+ */
+
+#define ELF_HWCAP	(elf_hwcap)
+extern unsigned int elf_hwcap;
+#include <asm/hwcap.h>
+
+/*
+ * This yields a string that ld.so will use to load implementation
+ * specific libraries for optimization.	 This is more specific in
+ * intent than poking at uname or /proc/cpuinfo.
+ */
+
+#define ELF_PLATFORM  __elf_platform
+extern const char *__elf_platform;
+
+#define ELF_PLAT_INIT(_r, load_addr)	do { \
+	_r->regs[1] = _r->regs[2] = _r->regs[3] = _r->regs[4] = 0;	\
+	_r->regs[5] = _r->regs[6] = _r->regs[7] = _r->regs[8] = 0;	\
+	_r->regs[9] = _r->regs[10] = _r->regs[11] = _r->regs[12] = 0;	\
+	_r->regs[13] = _r->regs[14] = _r->regs[15] = _r->regs[16] = 0;	\
+	_r->regs[17] = _r->regs[18] = _r->regs[19] = _r->regs[20] = 0;	\
+	_r->regs[21] = _r->regs[22] = _r->regs[23] = _r->regs[24] = 0;	\
+	_r->regs[25] = _r->regs[26] = _r->regs[27] = _r->regs[28] = 0;	\
+	_r->regs[29] = _r->regs[30] = _r->regs[31] = 0;			\
+} while (0)
+
+/*
+ * This is the location that an ET_DYN program is loaded if exec'ed. Typical
+ * use of this is to invoke "./ld.so someprog" to test out a new version of
+ * the loader. We need to make sure that it is out of the way of the program
+ * that it will "exec", and that there is sufficient room for the brk.
+ */
+
+#define ELF_ET_DYN_BASE		(TASK_SIZE / 3 * 2)
+
+/* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */
+#define ARCH_DLINFO							\
+do {									\
+	NEW_AUX_ENT(AT_SYSINFO_EHDR,					\
+		    (unsigned long)current->mm->context.vdso);		\
+} while (0)
+
+#define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
+struct linux_binprm;
+extern int arch_setup_additional_pages(struct linux_binprm *bprm,
+				       int uses_interp);
+
+struct arch_elf_state {
+	int fp_abi;
+	int interp_fp_abi;
+};
+
+#define LOONGARCH_ABI_FP_ANY	(0)
+
+#define INIT_ARCH_ELF_STATE {			\
+	.fp_abi = LOONGARCH_ABI_FP_ANY,		\
+	.interp_fp_abi = LOONGARCH_ABI_FP_ANY,	\
+}
+
+#define elf_read_implies_exec(ex, exec_stk) (exec_stk == EXSTACK_DEFAULT)
+
+extern int arch_elf_pt_proc(void *ehdr, void *phdr, struct file *elf,
+			    bool is_interp, struct arch_elf_state *state);
+
+extern int arch_check_elf(void *ehdr, bool has_interpreter, void *interp_ehdr,
+			  struct arch_elf_state *state);
+
+extern void loongarch_set_personality_fcsr(struct arch_elf_state *state);
+
+#endif /* _ASM_ELF_H */

arch/loongarch/include/asm/exec.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef _ASM_EXEC_H
+#define _ASM_EXEC_H
+
+extern unsigned long arch_align_stack(unsigned long sp);
+
+#endif /* _ASM_EXEC_H */

arch/loongarch/include/asm/module.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef _ASM_MODULE_H
+#define _ASM_MODULE_H
+
+#include <asm/inst.h>
+#include <asm-generic/module.h>
+
+#define RELA_STACK_DEPTH 16
+
+struct mod_section {
+	Elf_Shdr *shdr;
+	int num_entries;
+	int max_entries;
+};
+
+struct mod_arch_specific {
+	struct mod_section plt;
+	struct mod_section plt_idx;
+};
+
+struct plt_entry {
+	u32 inst_lu12iw;
+	u32 inst_lu32id;
+	u32 inst_lu52id;
+	u32 inst_jirl;
+};
+
+struct plt_idx_entry {
+	unsigned long symbol_addr;
+};
+
+Elf_Addr module_emit_plt_entry(struct module *mod, unsigned long val);
+
+static inline struct plt_entry emit_plt_entry(unsigned long val)
+{
+	u32 lu12iw, lu32id, lu52id, jirl;
+
+	lu12iw = (lu12iw_op << 25 | (((val >> 12) & 0xfffff) << 5) | LOONGARCH_GPR_T1);
+	lu32id = larch_insn_gen_lu32id(LOONGARCH_GPR_T1, ADDR_IMM(val, LU32ID));
+	lu52id = larch_insn_gen_lu52id(LOONGARCH_GPR_T1, LOONGARCH_GPR_T1, ADDR_IMM(val, LU52ID));
+	jirl = larch_insn_gen_jirl(0, LOONGARCH_GPR_T1, 0, (val & 0xfff));
+
+	return (struct plt_entry) { lu12iw, lu32id, lu52id, jirl };
+}
+
+static inline struct plt_idx_entry emit_plt_idx_entry(unsigned long val)
+{
+	return (struct plt_idx_entry) { val };
+}
+
+static inline int get_plt_idx(unsigned long val, const struct mod_section *sec)
+{
+	int i;
+	struct plt_idx_entry *plt_idx = (struct plt_idx_entry *)sec->shdr->sh_addr;
+
+	for (i = 0; i < sec->num_entries; i++) {
+		if (plt_idx[i].symbol_addr == val)
+			return i;
+	}
+
+	return -1;
+}
+
+static inline struct plt_entry *get_plt_entry(unsigned long val,
+				      const struct mod_section *sec_plt,
+				      const struct mod_section *sec_plt_idx)
+{
+	int plt_idx = get_plt_idx(val, sec_plt_idx);
+	struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr;
+
+	if (plt_idx < 0)
+		return NULL;
+
+	return plt + plt_idx;
+}
+
+#endif /* _ASM_MODULE_H */

arch/loongarch/include/asm/module.lds.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2020-2022 Loongson Technology Corporation Limited */
+SECTIONS {
+	. = ALIGN(4);
+	.plt : { BYTE(0) }
+	.plt.idx : { BYTE(0) }
+}

arch/loongarch/include/asm/vermagic.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef _ASM_VERMAGIC_H
+#define _ASM_VERMAGIC_H
+
+#define MODULE_PROC_FAMILY "LOONGARCH "
+
+#ifdef CONFIG_32BIT
+#define MODULE_KERNEL_TYPE "32BIT "
+#elif defined CONFIG_64BIT
+#define MODULE_KERNEL_TYPE "64BIT "
+#endif
+
+#define MODULE_ARCH_VERMAGIC \
+	MODULE_PROC_FAMILY MODULE_KERNEL_TYPE
+
+#endif /* _ASM_VERMAGIC_H */

arch/loongarch/include/uapi/asm/auxvec.h

···
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ * Author: Hanlu Li <[e-mail]>
+ *         Huacai Chen <[e-mail]>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#ifndef __ASM_AUXVEC_H
+#define __ASM_AUXVEC_H
+
+/* Location of VDSO image. */
+#define AT_SYSINFO_EHDR		33
+
+#define AT_VECTOR_SIZE_ARCH 1 /* entries in ARCH_DLINFO */
+
+#endif /* __ASM_AUXVEC_H */

arch/loongarch/include/uapi/asm/hwcap.h

···
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_ASM_HWCAP_H
+#define _UAPI_ASM_HWCAP_H
+
+/* HWCAP flags */
+#define HWCAP_LOONGARCH_CPUCFG		(1 << 0)
+#define HWCAP_LOONGARCH_LAM		(1 << 1)
+#define HWCAP_LOONGARCH_UAL		(1 << 2)
+#define HWCAP_LOONGARCH_FPU		(1 << 3)
+#define HWCAP_LOONGARCH_LSX		(1 << 4)
+#define HWCAP_LOONGARCH_LASX		(1 << 5)
+#define HWCAP_LOONGARCH_CRC32		(1 << 6)
+#define HWCAP_LOONGARCH_COMPLEX		(1 << 7)
+#define HWCAP_LOONGARCH_CRYPTO		(1 << 8)
+#define HWCAP_LOONGARCH_LVZ		(1 << 9)
+#define HWCAP_LOONGARCH_LBT_X86		(1 << 10)
+#define HWCAP_LOONGARCH_LBT_ARM		(1 << 11)
+#define HWCAP_LOONGARCH_LBT_MIPS	(1 << 12)
+
+#endif /* _UAPI_ASM_HWCAP_H */

arch/loongarch/kernel/elf.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: Huacai Chen <[e-mail]>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/binfmts.h>
+#include <linux/elf.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+
+#include <asm/cpu-features.h>
+#include <asm/cpu-info.h>
+
+int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf,
+		     bool is_interp, struct arch_elf_state *state)
+{
+	return 0;
+}
+
+int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr,
+		   struct arch_elf_state *state)
+{
+	return 0;
+}
+
+void loongarch_set_personality_fcsr(struct arch_elf_state *state)
+{
+	current->thread.fpu.fcsr = boot_cpu_data.fpu_csr0;
+}

arch/loongarch/kernel/inst.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#include <asm/inst.h>
+
+u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm)
+{
+	union loongarch_instruction insn;
+
+	insn.reg1i20_format.opcode = lu32id_op;
+	insn.reg1i20_format.rd = rd;
+	insn.reg1i20_format.immediate = imm;
+
+	return insn.word;
+}
+
+u32 larch_insn_gen_lu52id(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm)
+{
+	union loongarch_instruction insn;
+
+	insn.reg2i12_format.opcode = lu52id_op;
+	insn.reg2i12_format.rd = rd;
+	insn.reg2i12_format.rj = rj;
+	insn.reg2i12_format.immediate = imm;
+
+	return insn.word;
+}
+
+u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, unsigned long pc, unsigned long dest)
+{
+	union loongarch_instruction insn;
+
+	insn.reg2i16_format.opcode = jirl_op;
+	insn.reg2i16_format.rd = rd;
+	insn.reg2i16_format.rj = rj;
+	insn.reg2i16_format.immediate = (dest - pc) >> 2;
+
+	return insn.word;
+}

arch/loongarch/kernel/module-sections.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/elf.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+Elf_Addr module_emit_plt_entry(struct module *mod, unsigned long val)
+{
+	int nr;
+	struct mod_section *plt_sec = &mod->arch.plt;
+	struct mod_section *plt_idx_sec = &mod->arch.plt_idx;
+	struct plt_entry *plt = get_plt_entry(val, plt_sec, plt_idx_sec);
+	struct plt_idx_entry *plt_idx;
+
+	if (plt)
+		return (Elf_Addr)plt;
+
+	nr = plt_sec->num_entries;
+
+	/* There is no duplicate entry, create a new one */
+	plt = (struct plt_entry *)plt_sec->shdr->sh_addr;
+	plt[nr] = emit_plt_entry(val);
+	plt_idx = (struct plt_idx_entry *)plt_idx_sec->shdr->sh_addr;
+	plt_idx[nr] = emit_plt_idx_entry(val);
+
+	plt_sec->num_entries++;
+	plt_idx_sec->num_entries++;
+	BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
+
+	return (Elf_Addr)&plt[nr];
+}
+
+static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y)
+{
+	return x->r_info == y->r_info && x->r_addend == y->r_addend;
+}
+
+static bool duplicate_rela(const Elf_Rela *rela, int idx)
+{
+	int i;
+
+	for (i = 0; i < idx; i++) {
+		if (is_rela_equal(&rela[i], &rela[idx]))
+			return true;
+	}
+
+	return false;
+}
+
+static void count_max_entries(Elf_Rela *relas, int num, unsigned int *plts)
+{
+	unsigned int i, type;
+
+	for (i = 0; i < num; i++) {
+		type = ELF_R_TYPE(relas[i].r_info);
+		if (type == R_LARCH_SOP_PUSH_PLT_PCREL) {
+			if (!duplicate_rela(relas, i))
+				(*plts)++;
+		}
+	}
+}
+
+int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
+			      char *secstrings, struct module *mod)
+{
+	unsigned int i, num_plts = 0;
+
+	/*
+	 * Find the empty .plt sections.
+	 */
+	for (i = 0; i < ehdr->e_shnum; i++) {
+		if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
+			mod->arch.plt.shdr = sechdrs + i;
+		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx"))
+			mod->arch.plt_idx.shdr = sechdrs + i;
+	}
+
+	if (!mod->arch.plt.shdr) {
+		pr_err("%s: module PLT section(s) missing\n", mod->name);
+		return -ENOEXEC;
+	}
+	if (!mod->arch.plt_idx.shdr) {
+		pr_err("%s: module PLT.IDX section(s) missing\n", mod->name);
+		return -ENOEXEC;
+	}
+
+	/* Calculate the maxinum number of entries */
+	for (i = 0; i < ehdr->e_shnum; i++) {
+		int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
+		Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
+		Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;
+
+		if (sechdrs[i].sh_type != SHT_RELA)
+			continue;
+
+		/* ignore relocations that operate on non-exec sections */
+		if (!(dst_sec->sh_flags & SHF_EXECINSTR))
+			continue;
+
+		count_max_entries(relas, num_rela, &num_plts);
+	}
+
+	mod->arch.plt.shdr->sh_type = SHT_NOBITS;
+	mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
+	mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES;
+	mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
+	mod->arch.plt.num_entries = 0;
+	mod->arch.plt.max_entries = num_plts;
+
+	mod->arch.plt_idx.shdr->sh_type = SHT_NOBITS;
+	mod->arch.plt_idx.shdr->sh_flags = SHF_ALLOC;
+	mod->arch.plt_idx.shdr->sh_addralign = L1_CACHE_BYTES;
+	mod->arch.plt_idx.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry);
+	mod->arch.plt_idx.num_entries = 0;
+	mod->arch.plt_idx.max_entries = num_plts;
+
+	return 0;
+}

arch/loongarch/kernel/module.c

···
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Author: Hanlu Li <[e-mail]>
+ *         Huacai Chen <[e-mail]>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#define pr_fmt(fmt) "kmod: " fmt
+
+#include <linux/moduleloader.h>
+#include <linux/elf.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/kernel.h>
+
+static inline bool signed_imm_check(long val, unsigned int bit)
+{
+	return -(1L << (bit - 1)) <= val && val < (1L << (bit - 1));
+}
+
+static inline bool unsigned_imm_check(unsigned long val, unsigned int bit)
+{
+	return val < (1UL << bit);
+}
+
+static int rela_stack_push(s64 stack_value, s64 *rela_stack, size_t *rela_stack_top)
+{
+	if (*rela_stack_top >= RELA_STACK_DEPTH)
+		return -ENOEXEC;
+
+	rela_stack[(*rela_stack_top)++] = stack_value;
+	pr_debug("%s stack_value = 0x%llx\n", __func__, stack_value);
+
+	return 0;
+}
+
+static int rela_stack_pop(s64 *stack_value, s64 *rela_stack, size_t *rela_stack_top)
+{
+	if (*rela_stack_top == 0)
+		return -ENOEXEC;
+
+	*stack_value = rela_stack[--(*rela_stack_top)];
+	pr_debug("%s stack_value = 0x%llx\n", __func__, *stack_value);
+
+	return 0;
+}
+
+static int apply_r_larch_none(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	return 0;
+}
+
+static int apply_r_larch_error(struct module *me, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	pr_err("%s: Unsupport relocation type %u, please add its support.\n", me->name, type);
+	return -EINVAL;
+}
+
+static int apply_r_larch_32(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	*location = v;
+	return 0;
+}
+
+static int apply_r_larch_64(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	*(Elf_Addr *)location = v;
+	return 0;
+}
+
+static int apply_r_larch_sop_push_pcrel(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	return rela_stack_push(v - (u64)location, rela_stack, rela_stack_top);
+}
+
+static int apply_r_larch_sop_push_absolute(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	return rela_stack_push(v, rela_stack, rela_stack_top);
+}
+
+static int apply_r_larch_sop_push_dup(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	int err = 0;
+	s64 opr1;
+
+	err = rela_stack_pop(&opr1, rela_stack, rela_stack_top);
+	if (err)
+		return err;
+	err = rela_stack_push(opr1, rela_stack, rela_stack_top);
+	if (err)
+		return err;
+	err = rela_stack_push(opr1, rela_stack, rela_stack_top);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int apply_r_larch_sop_push_plt_pcrel(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	ptrdiff_t offset = (void *)v - (void *)location;
+
+	if (offset >= SZ_128M)
+		v = module_emit_plt_entry(mod, v);
+
+	if (offset < -SZ_128M)
+		v = module_emit_plt_entry(mod, v);
+
+	return apply_r_larch_sop_push_pcrel(mod, location, v, rela_stack, rela_stack_top, type);
+}
+
+static int apply_r_larch_sop(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	int err = 0;
+	s64 opr1, opr2, opr3;
+
+	if (type == R_LARCH_SOP_IF_ELSE) {
+		err = rela_stack_pop(&opr3, rela_stack, rela_stack_top);
+		if (err)
+			return err;
+	}
+
+	err = rela_stack_pop(&opr2, rela_stack, rela_stack_top);
+	if (err)
+		return err;
+	err = rela_stack_pop(&opr1, rela_stack, rela_stack_top);
+	if (err)
+		return err;
+
+	switch (type) {
+	case R_LARCH_SOP_AND:
+		err = rela_stack_push(opr1 & opr2, rela_stack, rela_stack_top);
+		break;
+	case R_LARCH_SOP_ADD:
+		err = rela_stack_push(opr1 + opr2, rela_stack, rela_stack_top);
+		break;
+	case R_LARCH_SOP_SUB:
+		err = rela_stack_push(opr1 - opr2, rela_stack, rela_stack_top);
+		break;
+	case R_LARCH_SOP_SL:
+		err = rela_stack_push(opr1 << opr2, rela_stack, rela_stack_top);
+		break;
+	case R_LARCH_SOP_SR:
+		err = rela_stack_push(opr1 >> opr2, rela_stack, rela_stack_top);
+		break;
+	case R_LARCH_SOP_IF_ELSE:
+		err = rela_stack_push(opr1 ? opr2 : opr3, rela_stack, rela_stack_top);
+		break;
+	default:
+		pr_err("%s: Unsupport relocation type %u\n", mod->name, type);
+		return -EINVAL;
+	}
+
+	return err;
+}
+
+static int apply_r_larch_sop_imm_field(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	int err = 0;
+	s64 opr1;
+	union loongarch_instruction *insn = (union loongarch_instruction *)location;
+
+	err = rela_stack_pop(&opr1, rela_stack, rela_stack_top);
+	if (err)
+		return err;
+
+	switch (type) {
+	case R_LARCH_SOP_POP_32_U_10_12:
+		if (!unsigned_imm_check(opr1, 12))
+			goto overflow;
+
+		/* (*(uint32_t *) PC) [21 ... 10] = opr [11 ... 0] */
+		insn->reg2i12_format.immediate = opr1 & 0xfff;
+		return 0;
+	case R_LARCH_SOP_POP_32_S_10_12:
+		if (!signed_imm_check(opr1, 12))
+			goto overflow;
+
+		insn->reg2i12_format.immediate = opr1 & 0xfff;
+		return 0;
+	case R_LARCH_SOP_POP_32_S_10_16:
+		if (!signed_imm_check(opr1, 16))
+			goto overflow;
+
+		insn->reg2i16_format.immediate = opr1 & 0xffff;
+		return 0;
+	case R_LARCH_SOP_POP_32_S_10_16_S2:
+		if (opr1 % 4)
+			goto unaligned;
+
+		if (!signed_imm_check(opr1, 18))
+			goto overflow;
+
+		insn->reg2i16_format.immediate = (opr1 >> 2) & 0xffff;
+		return 0;
+	case R_LARCH_SOP_POP_32_S_5_20:
+		if (!signed_imm_check(opr1, 20))
+			goto overflow;
+
+		insn->reg1i20_format.immediate = (opr1) & 0xfffff;
+		return 0;
+	case R_LARCH_SOP_POP_32_S_0_5_10_16_S2:
+		if (opr1 % 4)
+			goto unaligned;
+
+		if (!signed_imm_check(opr1, 23))
+			goto overflow;
+
+		opr1 >>= 2;
+		insn->reg1i21_format.immediate_l = opr1 & 0xffff;
+		insn->reg1i21_format.immediate_h = (opr1 >> 16) & 0x1f;
+		return 0;
+	case R_LARCH_SOP_POP_32_S_0_10_10_16_S2:
+		if (opr1 % 4)
+			goto unaligned;
+
+		if (!signed_imm_check(opr1, 28))
+			goto overflow;
+
+		opr1 >>= 2;
+		insn->reg0i26_format.immediate_l = opr1 & 0xffff;
+		insn->reg0i26_format.immediate_h = (opr1 >> 16) & 0x3ff;
+		return 0;
+	case R_LARCH_SOP_POP_32_U:
+		if (!unsigned_imm_check(opr1, 32))
+			goto overflow;
+
+		/* (*(uint32_t *) PC) = opr */
+		*location = (u32)opr1;
+		return 0;
+	default:
+		pr_err("%s: Unsupport relocation type %u\n", mod->name, type);
+		return -EINVAL;
+	}
+
+overflow:
+	pr_err("module %s: opr1 = 0x%llx overflow! dangerous %s (%u) relocation\n",
+		mod->name, opr1, __func__, type);
+	return -ENOEXEC;
+
+unaligned:
+	pr_err("module %s: opr1 = 0x%llx unaligned! dangerous %s (%u) relocation\n",
+		mod->name, opr1, __func__, type);
+	return -ENOEXEC;
+}
+
+static int apply_r_larch_add_sub(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type)
+{
+	switch (type) {
+	case R_LARCH_ADD32:
+		*(s32 *)location += v;
+		return 0;
+	case R_LARCH_ADD64:
+		*(s64 *)location += v;
+		return 0;
+	case R_LARCH_SUB32:
+		*(s32 *)location -= v;
+		return 0;
+	case R_LARCH_SUB64:
+		*(s64 *)location -= v;
+		return 0;
+	default:
+		pr_err("%s: Unsupport relocation type %u\n", mod->name, type);
+		return -EINVAL;
+	}
+}
+
+/*
+ * reloc_handlers_rela() - Apply a particular relocation to a module
+ * @mod: the module to apply the reloc to
+ * @location: the address at which the reloc is to be applied
+ * @v: the value of the reloc, with addend for RELA-style
+ * @rela_stack: the stack used for store relocation info, LOCAL to THIS module
+ * @rela_stac_top: where the stack operation(pop/push) applies to
+ *
+ * Return: 0 upon success, else -ERRNO
+ */
+typedef int (*reloc_rela_handler)(struct module *mod, u32 *location, Elf_Addr v,
+			s64 *rela_stack, size_t *rela_stack_top, unsigned int type);
+
+/* The handlers for known reloc types */
+static reloc_rela_handler reloc_rela_handlers[] = {
+	[R_LARCH_NONE ... R_LARCH_SUB64]		     = apply_r_larch_error,
+
+	[R_LARCH_NONE]					     = apply_r_larch_none,
+	[R_LARCH_32]					     = apply_r_larch_32,
+	[R_LARCH_64]					     = apply_r_larch_64,
+	[R_LARCH_MARK_LA]				     = apply_r_larch_none,
+	[R_LARCH_MARK_PCREL]				     = apply_r_larch_none,
+	[R_LARCH_SOP_PUSH_PCREL]			     = apply_r_larch_sop_push_pcrel,
+	[R_LARCH_SOP_PUSH_ABSOLUTE]			     = apply_r_larch_sop_push_absolute,
+	[R_LARCH_SOP_PUSH_DUP]				     = apply_r_larch_sop_push_dup,
+	[R_LARCH_SOP_PUSH_PLT_PCREL]			     = apply_r_larch_sop_push_plt_pcrel,
+	[R_LARCH_SOP_SUB ... R_LARCH_SOP_IF_ELSE] 	     = apply_r_larch_sop,
+	[R_LARCH_SOP_POP_32_S_10_5 ... R_LARCH_SOP_POP_32_U] = apply_r_larch_sop_imm_field,
+	[R_LARCH_ADD32 ... R_LARCH_SUB64]		     = apply_r_larch_add_sub,
+};
+
+int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
+		       unsigned int symindex, unsigned int relsec,
+		       struct module *mod)
+{
+	int i, err;
+	unsigned int type;
+	s64 rela_stack[RELA_STACK_DEPTH];
+	size_t rela_stack_top = 0;
+	reloc_rela_handler handler;
+	void *location;
+	Elf_Addr v;
+	Elf_Sym *sym;
+	Elf_Rela *rel = (void *) sechdrs[relsec].sh_addr;
+
+	pr_debug("%s: Applying relocate section %u to %u\n", __func__, relsec,
+	       sechdrs[relsec].sh_info);
+
+	rela_stack_top = 0;
+	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
+		/* This is where to make the change */
+		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr + rel[i].r_offset;
+		/* This is the symbol it is referring to */
+		sym = (Elf_Sym *)sechdrs[symindex].sh_addr + ELF_R_SYM(rel[i].r_info);
+		if (IS_ERR_VALUE(sym->st_value)) {
+			/* Ignore unresolved weak symbol */
+			if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
+				continue;
+			pr_warn("%s: Unknown symbol %s\n", mod->name, strtab + sym->st_name);
+			return -ENOENT;
+		}
+
+		type = ELF_R_TYPE(rel[i].r_info);
+
+		if (type < ARRAY_SIZE(reloc_rela_handlers))
+			handler = reloc_rela_handlers[type];
+		else
+			handler = NULL;
+
+		if (!handler) {
+			pr_err("%s: Unknown relocation type %u\n", mod->name, type);
+			return -EINVAL;
+		}
+
+		pr_debug("type %d st_value %llx r_addend %llx loc %llx\n",
+		       (int)ELF_R_TYPE(rel[i].r_info),
+		       sym->st_value, rel[i].r_addend, (u64)location);
+
+		v = sym->st_value + rel[i].r_addend;
+		err = handler(mod, location, v, rela_stack, &rela_stack_top, type);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+void *module_alloc(unsigned long size)
+{
+	return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
+			GFP_KERNEL, PAGE_KERNEL, 0, NUMA_NO_NODE, __builtin_return_address(0));
+}