[PATCH v2 10/13] riscv: alternative: patch alternatives in the vDSO

Jisheng Zhang
2022-12-04T17:57:57Z

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>
---
arch/riscv/include/asm/vdso.h | 4 ++++
arch/riscv/kernel/alternative.c | 25 +++++++++++++++++++++++++
arch/riscv/kernel/vdso.c | 5 -----
arch/riscv/kernel/vdso/vdso.lds.S | 7 +++++++
4 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/vdso.h b/arch/riscv/include/asm/vdso.h
index af981426fe0f..b6ff7473fb8a 100644
--- 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 9d88375624b5..eaf7ddaba54c 100644
--- 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>
@@ -187,6 +189,27 @@ static void __init_or_module _apply_alternatives(struct alt_entry *begin,
stage);
}

+static void __init apply_vdso_alternatives(void)
+{
+ const struct elf64_hdr *hdr;
+ const struct elf64_shdr *shdr;
+ const struct elf64_shdr *alt;
+ struct alt_entry *begin, *end;
+
+ hdr = (struct elf64_hdr *)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);
+}
+
void __init apply_boot_alternatives(void)
{
/* If called on non-boot cpu things could go wrong */
@@ -195,6 +218,8 @@ 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 123d05255fcf..1f47bc6566cf 100644
--- 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 150b1a572e61..4a0606633290 100644
--- 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.*)
--
2.37.2