riscv: implement module alternatives

This allows alternatives to also be applied when loading modules
and follows the implementation of other architectures (e.g. arm64).

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-4-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index c29cef90d1dd..91fe16bfaa07 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -11,6 +11,7 @@
 #include <linux/vmalloc.h>
 #include <linux/sizes.h>
 #include <linux/pgtable.h>
+#include <asm/alternative.h>
 #include <asm/sections.h>
 
 /*
@@ -427,3 +428,31 @@ void *module_alloc(unsigned long size)
 				    __builtin_return_address(0));
 }
 #endif
+
+static const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
+				    const Elf_Shdr *sechdrs,
+				    const char *name)
+{
+	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(name, secstrs + s->sh_name) == 0)
+			return s;
+	}
+
+	return NULL;
+}
+
+int module_finalize(const Elf_Ehdr *hdr,
+		    const Elf_Shdr *sechdrs,
+		    struct module *me)
+{
+	const Elf_Shdr *s;
+
+	s = find_section(hdr, sechdrs, ".alternative");
+	if (s)
+		apply_module_alternatives((void *)s->sh_addr, s->sh_size);
+
+	return 0;
+}