LoongArch: Add alternative runtime patching mechanism

Introduce the "alternative" mechanism from ARM64 and x86 for LoongArch
to apply runtime patching. The main purpose of this patch is to provide
a framework. In future we can use this mechanism (i.e., the ALTERNATIVE
and ALTERNATIVE_2 macros) to optimize hotspot functions according to cpu
features.

Signed-off-by: Jun Yi <yijun@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/loongarch/kernel/module.c b/arch/loongarch/kernel/module.c
index 097595b2fc14..825fcf77f9e7 100644
--- a/arch/loongarch/kernel/module.c
+++ b/arch/loongarch/kernel/module.c
@@ -17,6 +17,7 @@
 #include <linux/fs.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
+#include <asm/alternative.h>
 
 static int rela_stack_push(s64 stack_value, s64 *rela_stack, size_t *rela_stack_top)
 {
@@ -456,3 +457,17 @@ 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));
 }
+
+int module_finalize(const Elf_Ehdr *hdr,
+		    const Elf_Shdr *sechdrs, struct module *mod)
+{
+	const Elf_Shdr *s, *se;
+	const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
+
+	for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
+		if (!strcmp(".altinstructions", secstrs + s->sh_name))
+			apply_alternatives((void *)s->sh_addr, (void *)s->sh_addr + s->sh_size);
+	}
+
+	return 0;
+}