[PATCH v7 04/13] riscv: implement module alternatives

Heiko Stuebner
2022-03-07T20:53:55Z

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>
---
arch/riscv/errata/sifive/errata.c | 7 ++++---
arch/riscv/include/asm/alternative.h | 3 ++-
arch/riscv/kernel/alternative.c | 18 +++++++++++++----
arch/riscv/kernel/module.c | 29 ++++++++++++++++++++++++++++
4 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
index 4fe03ac41fd7..42457efcaaa3 100644
--- 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 +55,7 @@ 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 +67,7 @@ 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;

@@ -79,7 +80,7 @@ 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,
+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)
{
diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
index 811bdd8027db..f0657b1b3174 100644
--- a/arch/riscv/include/asm/alternative.h
+++ b/arch/riscv/include/asm/alternative.h
@@ -18,8 +18,10 @@
#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 */
@@ -37,6 +39,5 @@ struct errata_checkfunc_id {
void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
unsigned long archid, unsigned long impid,
unsigned int stage);
-
#endif
#endif
diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index 02db62f55bac..223770b3945c 100644
--- 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 68a9e3d1fe16..a778abd5b8b9 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>

static int apply_r_riscv_32_rela(struct module *me, u32 *location, Elf_Addr v)
@@ -416,3 +417,31 @@ 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;
+}
--
2.30.2