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x86/srso: Add IBPB

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Upstream commit: 233d6f68b98d480a7c42ebe78c38f79d44741ca9

Add the option to mitigate using IBPB on a kernel entry. Pull in the
Retbleed alternative so that the IBPB call from there can be used. Also,
if Retbleed mitigation is done using IBPB, the same mitigation can and
must be used here.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Borislav Petkov (AMD) 2023-07-06 15:04:35 +02:00 • committed by Greg Kroah-Hartman
parent 98f62883e7
commit 79c8091888
2 changed files with 25 additions and 1 deletions
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3
arch/x86/include/asm/nospec-branch.h
View file

@ -185,7 +185,8 @@
* where we have a stack but before any RET instruction.
*/
.macro UNTRAIN_RET
#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY)
#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
defined(CONFIG_CPU_SRSO)
ANNOTATE_UNRET_END
ALTERNATIVE_2 "", \
CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \

23
arch/x86/kernel/cpu/bugs.c
View file

@ -2315,18 +2315,21 @@ enum srso_mitigation {
SRSO_MITIGATION_NONE,
SRSO_MITIGATION_MICROCODE,
SRSO_MITIGATION_SAFE_RET,
SRSO_MITIGATION_IBPB,
};
enum srso_mitigation_cmd {
SRSO_CMD_OFF,
SRSO_CMD_MICROCODE,
SRSO_CMD_SAFE_RET,
SRSO_CMD_IBPB,
};
static const char * const srso_strings[] = {
[SRSO_MITIGATION_NONE] = "Vulnerable",
[SRSO_MITIGATION_MICROCODE] = "Mitigation: microcode",
[SRSO_MITIGATION_SAFE_RET] = "Mitigation: safe RET",
[SRSO_MITIGATION_IBPB] = "Mitigation: IBPB",
};
static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE;
@ -2343,6 +2346,8 @@ static int __init srso_parse_cmdline(char *str)
srso_cmd = SRSO_CMD_MICROCODE;
else if (!strcmp(str, "safe-ret"))
srso_cmd = SRSO_CMD_SAFE_RET;
else if (!strcmp(str, "ibpb"))
srso_cmd = SRSO_CMD_IBPB;
else
pr_err("Ignoring unknown SRSO option (%s).", str);
@ -2384,6 +2389,14 @@ static void __init srso_select_mitigation(void)
setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
}
if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
if (has_microcode) {
pr_err("Retbleed IBPB mitigation enabled, using same for SRSO\n");
srso_mitigation = SRSO_MITIGATION_IBPB;
goto pred_cmd;
}
}
switch (srso_cmd) {
case SRSO_CMD_OFF:
return;
@ -2408,6 +2421,16 @@ static void __init srso_select_mitigation(void)
}
break;
case SRSO_CMD_IBPB:
if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) {
if (has_microcode) {
setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB);
srso_mitigation = SRSO_MITIGATION_IBPB;
}
} else {
pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
goto pred_cmd;
}
default:
break;
}