LoongArch: Add ELF and module support

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

Cc: Jessica Yu <jeyu@kernel.org>
Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 121 insertions, 0 deletions

diff --git a/arch/loongarch/kernel/module-sections.c b/arch/loongarch/kernel/module-sections.c
new file mode 100644
index 000000000000..6d498288977d
--- /dev/null
+++ b/arch/loongarch/kernel/module-sections.c
@@ -0,0 +1,121 @@
+// 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;
+}