summaryrefslogtreecommitdiffstats
path: root/arch/s390/kernel/nospec-branch.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/s390/kernel/nospec-branch.c')
-rw-r--r--arch/s390/kernel/nospec-branch.c44
1 files changed, 20 insertions, 24 deletions
diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c
index 46d49a11663f..8ad6a7128b3a 100644
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -1,7 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/module.h>
#include <linux/device.h>
-#include <linux/cpu.h>
#include <asm/nospec-branch.h>
static int __init nobp_setup_early(char *str)
@@ -44,24 +43,6 @@ static int __init nospec_report(void)
}
arch_initcall(nospec_report);
-#ifdef CONFIG_SYSFS
-ssize_t cpu_show_spectre_v1(struct device *dev,
- struct device_attribute *attr, char *buf)
-{
- return sprintf(buf, "Mitigation: __user pointer sanitization\n");
-}
-
-ssize_t cpu_show_spectre_v2(struct device *dev,
- struct device_attribute *attr, char *buf)
-{
- if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable)
- return sprintf(buf, "Mitigation: execute trampolines\n");
- if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
- return sprintf(buf, "Mitigation: limited branch prediction.\n");
- return sprintf(buf, "Vulnerable\n");
-}
-#endif
-
#ifdef CONFIG_EXPOLINE
int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);
@@ -112,7 +93,6 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end)
s32 *epo;
/* Second part of the instruction replace is always a nop */
- memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x00, 0x00 }, 4);
for (epo = start; epo < end; epo++) {
instr = (u8 *) epo + *epo;
if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04)
@@ -133,18 +113,34 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end)
br = thunk + (*(int *)(thunk + 2)) * 2;
else
continue;
- if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0)
+ /* Check for unconditional branch 0x07f? or 0x47f???? */
+ if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0)
continue;
+
+ memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4);
switch (type) {
case BRCL_EXPOLINE:
- /* brcl to thunk, replace with br + nop */
insnbuf[0] = br[0];
insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
+ if (br[0] == 0x47) {
+ /* brcl to b, replace with bc + nopr */
+ insnbuf[2] = br[2];
+ insnbuf[3] = br[3];
+ } else {
+ /* brcl to br, replace with bcr + nop */
+ }
break;
case BRASL_EXPOLINE:
- /* brasl to thunk, replace with basr + nop */
- insnbuf[0] = 0x0d;
insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
+ if (br[0] == 0x47) {
+ /* brasl to b, replace with bas + nopr */
+ insnbuf[0] = 0x4d;
+ insnbuf[2] = br[2];
+ insnbuf[3] = br[3];
+ } else {
+ /* brasl to br, replace with basr + nop */
+ insnbuf[0] = 0x0d;
+ }
break;
}