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authorVasily Gorbik <gor@linux.vnet.ibm.com>2017-10-12 13:01:47 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-10-18 14:11:29 +0200
commit686140a1a9c41d85a4212a1c26d671139b76404b (patch)
tree2d19e98601a9d9855f7eac6cca6cb364f5a9d650 /arch/s390/kernel/module.c
parent76b3b62ade4baa13b270bafb96be730ebff913f0 (diff)
downloadlinux-686140a1a9c41d85a4212a1c26d671139b76404b.tar.bz2
s390: introduce CPU alternatives
Implement CPU alternatives, which allows to optionally patch newer instructions at runtime, based on CPU facilities availability. A new kernel boot parameter "noaltinstr" disables patching. Current implementation is derived from x86 alternatives. Although ideal instructions padding (when altinstr is longer then oldinstr) is added at compile time, and no oldinstr nops optimization has to be done at runtime. Also couple of compile time sanity checks are done: 1. oldinstr and altinstr must be <= 254 bytes long, 2. oldinstr and altinstr must not have an odd length. alternative(oldinstr, altinstr, facility); alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2); Both compile time and runtime padding consists of either 6/4/2 bytes nop or a jump (brcl) + 2 bytes nop filler if padding is longer then 6 bytes. .altinstructions and .altinstr_replacement sections are part of __init_begin : __init_end region and are freed after initialization. Signed-off-by: Vasily Gorbik <gor@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/module.c')
-rw-r--r--arch/s390/kernel/module.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index 1a27f307a920..6d9f73bb4142 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -31,6 +31,7 @@
#include <linux/kernel.h>
#include <linux/moduleloader.h>
#include <linux/bug.h>
+#include <asm/alternative.h>
#if 0
#define DEBUGP printk
@@ -429,6 +430,22 @@ int module_finalize(const Elf_Ehdr *hdr,
const Elf_Shdr *sechdrs,
struct module *me)
{
+ const Elf_Shdr *s;
+ char *secstrings;
+
+ if (IS_ENABLED(CONFIG_ALTERNATIVES)) {
+ secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
+ for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
+ if (!strcmp(".altinstructions",
+ secstrings + s->sh_name)) {
+ /* patch .altinstructions */
+ void *aseg = (void *)s->sh_addr;
+
+ apply_alternatives(aseg, aseg + s->sh_size);
+ }
+ }
+ }
+
jump_label_apply_nops(me);
return 0;
}