Re: [PATCH 03/12] riscv: implement module alternatives

[Guo Ren <guoren@kernel.org>]

Reviewed-by: Guo Ren <guoren@kernel.org>

On Thu, May 12, 2022 at 3:29 AM Heiko Stuebner <heiko@sntech.de> wrote:
>
> 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>
> ---
>  arch/riscv/errata/sifive/errata.c    | 14 +++++++++-----
>  arch/riscv/include/asm/alternative.h |  3 +++
>  arch/riscv/kernel/alternative.c      | 18 +++++++++++++----
>  arch/riscv/kernel/module.c           | 29 ++++++++++++++++++++++++++++
>  4 files changed, 55 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
> index 4fe03ac41fd7..3e39587a49dc 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 +55,8 @@ 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 0ff550667e94..0859529ff08e 100644
> --- 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 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 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;
> +}
> --
> 2.35.1
>


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/