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>

diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
index 4fe03ac..3e39587 100644 (file)
--- a/arch/riscv/errata/sifive/errata.c
+++ b/arch/riscv/errata/sifive/errata.c
@@ -4,6 +4,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/string.h>
 #include <linux/bug.h>
 #include <asm/patch.h>
@@ -54,7 +55,8 @@ static struct errata_info_t errata_list[ERRATA_SIFIVE_NUMBER] = {
        },
 };
 
-static u32 __init sifive_errata_probe(unsigned long archid, unsigned long impid)
+static u32 __init_or_module sifive_errata_probe(unsigned long archid,
+                                               unsigned long impid)
 {
        int idx;
        u32 cpu_req_errata = 0;
@@ -66,7 +68,7 @@ static u32 __init sifive_errata_probe(unsigned long archid, unsigned long impid)
        return cpu_req_errata;
 }
 
-static void __init warn_miss_errata(u32 miss_errata)
+static void __init_or_module warn_miss_errata(u32 miss_errata)
 {
        int i;
 
@@ -79,9 +81,11 @@ static void __init warn_miss_errata(u32 miss_errata)
        pr_warn("----------------------------------------------------------------\n");
 }
 
-void __init sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
-                                    unsigned long archid, unsigned long impid,
-                                    unsigned int stage)
+void __init_or_module sifive_errata_patch_func(struct alt_entry *begin,
+                                              struct alt_entry *end,
+                                              unsigned long archid,
+                                              unsigned long impid,
+                                              unsigned int stage)
 {
        struct alt_entry *alt;
        u32 cpu_req_errata = sifive_errata_probe(archid, impid);

diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
index 0ff5506..0859529 100644 (file)
--- a/arch/riscv/include/asm/alternative.h
+++ b/arch/riscv/include/asm/alternative.h
@@ -20,8 +20,10 @@
 #include <asm/hwcap.h>
 
 #define RISCV_ALTERNATIVES_BOOT                0 /* alternatives applied during regular boot */
+#define RISCV_ALTERNATIVES_MODULE      1 /* alternatives applied during module-init */
 
 void __init apply_boot_alternatives(void);
+void apply_module_alternatives(void *start, size_t length);
 
 struct alt_entry {
        void *old_ptr;           /* address of original instruciton or data  */
@@ -43,6 +45,7 @@ void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
 #else /* CONFIG_RISCV_ALTERNATIVE */
 
 static inline void apply_boot_alternatives(void) { }
+static inline void apply_module_alternatives(void *start, size_t length) { }
 
 #endif /* CONFIG_RISCV_ALTERNATIVE */
 

diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index 02db62f..223770b 100644 (file)
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/module.h>
 #include <linux/cpu.h>
 #include <linux/uaccess.h>
 #include <asm/alternative.h>
@@ -23,7 +24,7 @@ static struct cpu_manufacturer_info_t {
 
 static void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
                                 unsigned long archid, unsigned long impid,
-                                unsigned int stage) __initdata;
+                                unsigned int stage) __initdata_or_module;
 
 static inline void __init riscv_fill_cpu_mfr_info(void)
 {
@@ -58,9 +59,9 @@ static void __init init_alternative(void)
  * a feature detect on the boot CPU). No need to worry about other CPUs
  * here.
  */
-static void __init _apply_alternatives(struct alt_entry *begin,
-                                      struct alt_entry *end,
-                                      unsigned int stage)
+static void __init_or_module _apply_alternatives(struct alt_entry *begin,
+                                                struct alt_entry *end,
+                                                unsigned int stage)
 {
        if (!vendor_patch_func)
                return;
@@ -81,3 +82,12 @@ void __init apply_boot_alternatives(void)
                            (struct alt_entry *)__alt_end,
                            RISCV_ALTERNATIVES_BOOT);
 }
+
+#ifdef CONFIG_MODULES
+void apply_module_alternatives(void *start, size_t length)
+{
+       _apply_alternatives((struct alt_entry *)start,
+                           (struct alt_entry *)(start + length),
+                           RISCV_ALTERNATIVES_MODULE);
+}
+#endif

diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index c29cef9..91fe16b 100644 (file)
--- 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;
+}