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UBUNTU: SAUCE: x86/speculation: Rename RETPOLINE_AMD to RETPOLINE_LFENCE
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The RETPOLINE_AMD name is unfortunate since it isn't necessarily
AMD only, in fact Hygon also uses it. Furthermore it will likely be
sufficient for some Intel processors. Therefore rename the thing to
RETPOLINE_LFENCE to better describe what it is.

Add the spectre_v2=retpoline,lfence option as an alias to
spectre_v2=retpoline,amd to preserve existing setups. However, the output
of /sys/devices/system/cpu/vulnerabilities/spectre_v2 will be changed.

  [ bp: Fix typos, massage. ]

Co-developed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
[fllinden@amazon.com: backported to 5.15]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
CVE-2022-0001
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
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Peter Zijlstra (Intel) authored and Thadeu Lima de Souza Cascardo committed Mar 7, 2022
1 parent c67aa40 commit 5974e74
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Showing 5 changed files with 27 additions and 20 deletions.
2 changes: 1 addition & 1 deletion arch/x86/include/asm/cpufeatures.h
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Original file line number Diff line number Diff line change
Expand Up @@ -204,7 +204,7 @@
/* FREE! ( 7*32+10) */
#define X86_FEATURE_PTI ( 7*32+11) /* Kernel Page Table Isolation enabled */
#define X86_FEATURE_RETPOLINE ( 7*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */
#define X86_FEATURE_RETPOLINE_AMD ( 7*32+13) /* "" AMD Retpoline mitigation for Spectre variant 2 */
#define X86_FEATURE_RETPOLINE_LFENCE ( 7*32+13) /* "" Use LFENCE for Spectre variant 2 */
#define X86_FEATURE_INTEL_PPIN ( 7*32+14) /* Intel Processor Inventory Number */
#define X86_FEATURE_CDP_L2 ( 7*32+15) /* Code and Data Prioritization L2 */
#define X86_FEATURE_MSR_SPEC_CTRL ( 7*32+16) /* "" MSR SPEC_CTRL is implemented */
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12 changes: 6 additions & 6 deletions arch/x86/include/asm/nospec-branch.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,7 +81,7 @@
#ifdef CONFIG_RETPOLINE
ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
__stringify(jmp __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_AMD
__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE
#else
jmp *%\reg
#endif
Expand All @@ -91,7 +91,7 @@
#ifdef CONFIG_RETPOLINE
ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; call *%\reg), \
__stringify(call __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \
__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *%\reg), X86_FEATURE_RETPOLINE_AMD
__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *%\reg), X86_FEATURE_RETPOLINE_LFENCE
#else
call *%\reg
#endif
Expand Down Expand Up @@ -133,7 +133,7 @@
"lfence;\n" \
ANNOTATE_RETPOLINE_SAFE \
"call *%[thunk_target]\n", \
X86_FEATURE_RETPOLINE_AMD)
X86_FEATURE_RETPOLINE_LFENCE)

# define THUNK_TARGET(addr) [thunk_target] "r" (addr)

Expand Down Expand Up @@ -163,7 +163,7 @@
"lfence;\n" \
ANNOTATE_RETPOLINE_SAFE \
"call *%[thunk_target]\n", \
X86_FEATURE_RETPOLINE_AMD)
X86_FEATURE_RETPOLINE_LFENCE)

# define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
#endif
Expand All @@ -175,8 +175,8 @@
/* The Spectre V2 mitigation variants */
enum spectre_v2_mitigation {
SPECTRE_V2_NONE,
SPECTRE_V2_RETPOLINE_GENERIC,
SPECTRE_V2_RETPOLINE_AMD,
SPECTRE_V2_RETPOLINE,
SPECTRE_V2_LFENCE,
SPECTRE_V2_IBRS_ENHANCED,
};

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29 changes: 18 additions & 11 deletions arch/x86/kernel/cpu/bugs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -627,7 +627,7 @@ enum spectre_v2_mitigation_cmd {
SPECTRE_V2_CMD_FORCE,
SPECTRE_V2_CMD_RETPOLINE,
SPECTRE_V2_CMD_RETPOLINE_GENERIC,
SPECTRE_V2_CMD_RETPOLINE_AMD,
SPECTRE_V2_CMD_RETPOLINE_LFENCE,
};

enum spectre_v2_user_cmd {
Expand Down Expand Up @@ -787,8 +787,8 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)

static const char * const spectre_v2_strings[] = {
[SPECTRE_V2_NONE] = "Vulnerable",
[SPECTRE_V2_RETPOLINE_GENERIC] = "Mitigation: Full generic retpoline",
[SPECTRE_V2_RETPOLINE_AMD] = "Mitigation: Full AMD retpoline",
[SPECTRE_V2_RETPOLINE] = "Mitigation: Retpolines",
[SPECTRE_V2_LFENCE] = "Mitigation: LFENCE",
[SPECTRE_V2_IBRS_ENHANCED] = "Mitigation: Enhanced IBRS",
};

Expand All @@ -800,7 +800,8 @@ static const struct {
{ "off", SPECTRE_V2_CMD_NONE, false },
{ "on", SPECTRE_V2_CMD_FORCE, true },
{ "retpoline", SPECTRE_V2_CMD_RETPOLINE, false },
{ "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_AMD, false },
{ "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false },
{ "retpoline,lfence", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false },
{ "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
{ "auto", SPECTRE_V2_CMD_AUTO, false },
};
Expand Down Expand Up @@ -838,13 +839,19 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
}

if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
!IS_ENABLED(CONFIG_RETPOLINE)) {
pr_err("%s selected but not compiled in. Switching to AUTO select\n", mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}

if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE) &&
!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n", mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}

spec_v2_print_cond(mitigation_options[i].option,
mitigation_options[i].secure);
return cmd;
Expand Down Expand Up @@ -879,9 +886,9 @@ static void __init spectre_v2_select_mitigation(void)
if (IS_ENABLED(CONFIG_RETPOLINE))
goto retpoline_auto;
break;
case SPECTRE_V2_CMD_RETPOLINE_AMD:
case SPECTRE_V2_CMD_RETPOLINE_LFENCE:
if (IS_ENABLED(CONFIG_RETPOLINE))
goto retpoline_amd;
goto retpoline_lfence;
break;
case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
if (IS_ENABLED(CONFIG_RETPOLINE))
Expand All @@ -898,17 +905,17 @@ static void __init spectre_v2_select_mitigation(void)
retpoline_auto:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
retpoline_amd:
retpoline_lfence:
if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
pr_err("Spectre mitigation: LFENCE not serializing, switching to generic retpoline\n");
goto retpoline_generic;
}
mode = SPECTRE_V2_RETPOLINE_AMD;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
mode = SPECTRE_V2_LFENCE;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE_LFENCE);
setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
} else {
retpoline_generic:
mode = SPECTRE_V2_RETPOLINE_GENERIC;
mode = SPECTRE_V2_RETPOLINE;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
}

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2 changes: 1 addition & 1 deletion arch/x86/lib/retpoline.S
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ SYM_FUNC_START(__x86_indirect_thunk_\reg)

ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
__stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \
__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_AMD
__stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE

SYM_FUNC_END(__x86_indirect_thunk_\reg)

Expand Down
2 changes: 1 addition & 1 deletion tools/arch/x86/include/asm/cpufeatures.h
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Original file line number Diff line number Diff line change
Expand Up @@ -204,7 +204,7 @@
/* FREE! ( 7*32+10) */
#define X86_FEATURE_PTI ( 7*32+11) /* Kernel Page Table Isolation enabled */
#define X86_FEATURE_RETPOLINE ( 7*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */
#define X86_FEATURE_RETPOLINE_AMD ( 7*32+13) /* "" AMD Retpoline mitigation for Spectre variant 2 */
#define X86_FEATURE_RETPOLINE_LFENCE ( 7*32+13) /* "" Use LFENCEs for Spectre variant 2 */
#define X86_FEATURE_INTEL_PPIN ( 7*32+14) /* Intel Processor Inventory Number */
#define X86_FEATURE_CDP_L2 ( 7*32+15) /* Code and Data Prioritization L2 */
#define X86_FEATURE_MSR_SPEC_CTRL ( 7*32+16) /* "" MSR SPEC_CTRL is implemented */
Expand Down

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