riscv: alternative: patch alternatives in the vDSO

Make it possible to use alternatives in the vDSO, so that better
implementations can be used if possible.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20230128172856.3814-11-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/include/asm/vdso.h b/arch/riscv/include/asm/vdso.h
index a7644f46d0e56e5f60ec38820b576ae22a4e7b68..f891478829a52c41e06240f67611694cc28197d9 100644 (file)
--- a/arch/riscv/include/asm/vdso.h
+++ b/arch/riscv/include/asm/vdso.h
@@ -28,8 +28,12 @@
 #define COMPAT_VDSO_SYMBOL(base, name)                                         \
        (void __user *)((unsigned long)(base) + compat__vdso_##name##_offset)
 
+extern char compat_vdso_start[], compat_vdso_end[];
+
 #endif /* CONFIG_COMPAT */
 
+extern char vdso_start[], vdso_end[];
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* CONFIG_MMU */

diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index 3d4f1f32c7f6c85259b8ce8f8a5c4898f1ed7230..fc341b69bf6204cf7a026b2e82f3e8d6c9a81a8d 100644 (file)
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -11,7 +11,9 @@
 #include <linux/cpu.h>
 #include <linux/uaccess.h>
 #include <asm/alternative.h>
+#include <asm/module.h>
 #include <asm/sections.h>
+#include <asm/vdso.h>
 #include <asm/vendorid_list.h>
 #include <asm/sbi.h>
 #include <asm/csr.h>
@@ -160,6 +162,31 @@ static void __init_or_module _apply_alternatives(struct alt_entry *begin,
                                stage);
 }
 
+#ifdef CONFIG_MMU
+static void __init apply_vdso_alternatives(void)
+{
+       const Elf_Ehdr *hdr;
+       const Elf_Shdr *shdr;
+       const Elf_Shdr *alt;
+       struct alt_entry *begin, *end;
+
+       hdr = (Elf_Ehdr *)vdso_start;
+       shdr = (void *)hdr + hdr->e_shoff;
+       alt = find_section(hdr, shdr, ".alternative");
+       if (!alt)
+               return;
+
+       begin = (void *)hdr + alt->sh_offset,
+       end = (void *)hdr + alt->sh_offset + alt->sh_size,
+
+       _apply_alternatives((struct alt_entry *)begin,
+                           (struct alt_entry *)end,
+                           RISCV_ALTERNATIVES_BOOT);
+}
+#else
+static void __init apply_vdso_alternatives(void) { }
+#endif
+
 void __init apply_boot_alternatives(void)
 {
        /* If called on non-boot cpu things could go wrong */
@@ -168,6 +195,8 @@ void __init apply_boot_alternatives(void)
        _apply_alternatives((struct alt_entry *)__alt_start,
                            (struct alt_entry *)__alt_end,
                            RISCV_ALTERNATIVES_BOOT);
+
+       apply_vdso_alternatives();
 }
 
 /*

diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
index e410275918ac4524649552c1f6e683a7129600b2..4e631c098f4d26cadb1f2a950900b1511edcc7d8 100644 (file)
--- a/arch/riscv/kernel/vdso.c
+++ b/arch/riscv/kernel/vdso.c
@@ -22,11 +22,6 @@ struct vdso_data {
 };
 #endif
 
-extern char vdso_start[], vdso_end[];
-#ifdef CONFIG_COMPAT
-extern char compat_vdso_start[], compat_vdso_end[];
-#endif
-
 enum vvar_pages {
        VVAR_DATA_PAGE_OFFSET,
        VVAR_TIMENS_PAGE_OFFSET,

diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index 150b1a572e6190e94d5353d024c5dec36c7e5ffb..4a060663329024feffbb82d7c5d663b1099f36ce 100644 (file)
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -40,6 +40,13 @@ SECTIONS
        . = 0x800;
        .text           : { *(.text .text.*) }          :text
 
+       . = ALIGN(4);
+       .alternative : {
+               __alt_start = .;
+               *(.alternative)
+               __alt_end = .;
+       }
+
        .data           : {
                *(.got.plt) *(.got)
                *(.data .data.* .gnu.linkonce.d.*)