[PATCH 5/7] s390/vdso: Allow alternatives in vdso code

Heiko Carstens
2024-09-13T13:05:51Z

Implement the infrastructure required to allow alternatives in vdso code.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
arch/s390/kernel/vdso.c | 19 +++++++++++++++++++
arch/s390/kernel/vdso64/vdso64.lds.S | 4 ++++
2 files changed, 23 insertions(+)

diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index 2f967ac2b8e3..8e4e6b316337 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -12,12 +12,14 @@
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
+#include <linux/module.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/time_namespace.h>
#include <linux/random.h>
#include <vdso/datapage.h>
+#include <asm/alternative.h>
#include <asm/vdso.h>

extern char vdso64_start[], vdso64_end[];
@@ -250,8 +252,25 @@ static struct page ** __init vdso_setup_pages(void *start, void *end)
return pagelist;
}

+static void vdso_apply_alternatives(void)
+{
+ const struct elf64_shdr *alt, *shdr;
+ struct alt_instr *start, *end;
+ const struct elf64_hdr *hdr;
+
+ hdr = (struct elf64_hdr *)vdso64_start;
+ shdr = (void *)hdr + hdr->e_shoff;
+ alt = find_section(hdr, shdr, ".altinstructions");
+ if (!alt)
+ return;
+ start = (void *)hdr + alt->sh_offset;
+ end = (void *)hdr + alt->sh_offset + alt->sh_size;
+ apply_alternatives(start, end);
+}
+
static int __init vdso_init(void)
{
+ vdso_apply_alternatives();
vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end);
if (IS_ENABLED(CONFIG_COMPAT))
vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end);
diff --git a/arch/s390/kernel/vdso64/vdso64.lds.S b/arch/s390/kernel/vdso64/vdso64.lds.S
index 37e2a505e81d..fa02c6ae3cac 100644
--- a/arch/s390/kernel/vdso64/vdso64.lds.S
+++ b/arch/s390/kernel/vdso64/vdso64.lds.S
@@ -42,6 +42,10 @@ SECTIONS
.rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
.rodata1 : { *(.rodata1) }

+ . = ALIGN(8);
+ .altinstructions : { *(.altinstructions) }
+ .altinstr_replacement : { *(.altinstr_replacement) }
+
.dynamic : { *(.dynamic) } :text :dynamic

.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
--
2.43.0