Release 4.15 arch/x86/kernel/cpu/bugs.c
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 1994 Linus Torvalds
*
* Cyrix stuff, June 1998 by:
* - Rafael R. Reilova (moved everything from head.S),
* <rreilova@ececs.uc.edu>
* - Channing Corn (tests & fixes),
* - Andrew D. Balsa (code cleanup).
*/
#include <linux/init.h>
#include <linux/utsname.h>
#include <linux/cpu.h>
#include <asm/nospec-branch.h>
#include <asm/cmdline.h>
#include <asm/bugs.h>
#include <asm/processor.h>
#include <asm/processor-flags.h>
#include <asm/fpu/internal.h>
#include <asm/msr.h>
#include <asm/paravirt.h>
#include <asm/alternative.h>
#include <asm/pgtable.h>
#include <asm/set_memory.h>
#include <asm/intel-family.h>
static void __init spectre_v2_select_mitigation(void);
void __init check_bugs(void)
{
identify_boot_cpu();
if (!IS_ENABLED(CONFIG_SMP)) {
pr_info("CPU: ");
print_cpu_info(&boot_cpu_data);
}
/* Select the proper spectre mitigation before patching alternatives */
spectre_v2_select_mitigation();
#ifdef CONFIG_X86_32
/*
* Check whether we are able to run this kernel safely on SMP.
*
* - i386 is no longer supported.
* - In order to run on anything without a TSC, we need to be
* compiled for a i486.
*/
if (boot_cpu_data.x86 < 4)
panic("Kernel requires i486+ for 'invlpg' and other features");
init_utsname()->machine[1] =
'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
alternative_instructions();
fpu__init_check_bugs();
#else /* CONFIG_X86_64 */
alternative_instructions();
/*
* Make sure the first 2MB area is not mapped by huge pages
* There are typically fixed size MTRRs in there and overlapping
* MTRRs into large pages causes slow downs.
*
* Right now we don't do that with gbpages because there seems
* very little benefit for that case.
*/
if (!direct_gbpages)
set_memory_4k((unsigned long)__va(0), 1);
#endif
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Borislav Petkov | 53 | 47.75% | 2 | 28.57% |
| Jeremy Fitzhardinge | 50 | 45.05% | 1 | 14.29% |
| David Woodhouse | 4 | 3.60% | 1 | 14.29% |
| Suresh B. Siddha | 2 | 1.80% | 1 | 14.29% |
| Ingo Molnar | 1 | 0.90% | 1 | 14.29% |
| Joe Perches | 1 | 0.90% | 1 | 14.29% |
| Total | 111 | 100.00% | 7 | 100.00% |
/* The kernel command line selection */
enum spectre_v2_mitigation_cmd {
SPECTRE_V2_CMD_NONE,
SPECTRE_V2_CMD_AUTO,
SPECTRE_V2_CMD_FORCE,
SPECTRE_V2_CMD_RETPOLINE,
SPECTRE_V2_CMD_RETPOLINE_GENERIC,
SPECTRE_V2_CMD_RETPOLINE_AMD,
};
static const char *spectre_v2_strings[] = {
[SPECTRE_V2_NONE] = "Vulnerable",
[SPECTRE_V2_RETPOLINE_MINIMAL] = "Vulnerable: Minimal generic ASM retpoline",
[SPECTRE_V2_RETPOLINE_MINIMAL_AMD] = "Vulnerable: Minimal AMD ASM retpoline",
[SPECTRE_V2_RETPOLINE_GENERIC] = "Mitigation: Full generic retpoline",
[SPECTRE_V2_RETPOLINE_AMD] = "Mitigation: Full AMD retpoline",
};
#undef pr_fmt
#define pr_fmt(fmt) "Spectre V2 mitigation: " fmt
static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
static void __init spec2_print_if_insecure(const char *reason)
{
if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
pr_info("%s\n", reason);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 26 | 100.00% | 1 | 100.00% |
| Total | 26 | 100.00% | 1 | 100.00% |
static void __init spec2_print_if_secure(const char *reason)
{
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
pr_info("%s\n", reason);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 27 | 100.00% | 1 | 100.00% |
| Total | 27 | 100.00% | 1 | 100.00% |
static inline bool retp_compiler(void)
{
return __is_defined(RETPOLINE);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 15 | 100.00% | 1 | 100.00% |
| Total | 15 | 100.00% | 1 | 100.00% |
static inline bool match_option(const char *arg, int arglen, const char *opt)
{
int len = strlen(opt);
return len == arglen && !strncmp(arg, opt, len);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 43 | 100.00% | 1 | 100.00% |
| Total | 43 | 100.00% | 1 | 100.00% |
static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
{
char arg[20];
int ret;
ret = cmdline_find_option(boot_command_line, "spectre_v2", arg,
sizeof(arg));
if (ret > 0) {
if (match_option(arg, ret, "off")) {
goto disable;
} else if (match_option(arg, ret, "on")) {
spec2_print_if_secure("force enabled on command line.");
return SPECTRE_V2_CMD_FORCE;
} else if (match_option(arg, ret, "retpoline")) {
spec2_print_if_insecure("retpoline selected on command line.");
return SPECTRE_V2_CMD_RETPOLINE;
} else if (match_option(arg, ret, "retpoline,amd")) {
if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
return SPECTRE_V2_CMD_AUTO;
}
spec2_print_if_insecure("AMD retpoline selected on command line.");
return SPECTRE_V2_CMD_RETPOLINE_AMD;
} else if (match_option(arg, ret, "retpoline,generic")) {
spec2_print_if_insecure("generic retpoline selected on command line.");
return SPECTRE_V2_CMD_RETPOLINE_GENERIC;
} else if (match_option(arg, ret, "auto")) {
return SPECTRE_V2_CMD_AUTO;
}
}
if (!cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
return SPECTRE_V2_CMD_AUTO;
disable:
spec2_print_if_insecure("disabled on command line.");
return SPECTRE_V2_CMD_NONE;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 205 | 100.00% | 1 | 100.00% |
| Total | 205 | 100.00% | 1 | 100.00% |
/* Check for Skylake-like CPUs (for RSB handling) */
static bool __init is_skylake_era(void)
{
if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
boot_cpu_data.x86 == 6) {
switch (boot_cpu_data.x86_model) {
case INTEL_FAM6_SKYLAKE_MOBILE:
case INTEL_FAM6_SKYLAKE_DESKTOP:
case INTEL_FAM6_SKYLAKE_X:
case INTEL_FAM6_KABYLAKE_MOBILE:
case INTEL_FAM6_KABYLAKE_DESKTOP:
return true;
}
}
return false;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 54 | 100.00% | 1 | 100.00% |
| Total | 54 | 100.00% | 1 | 100.00% |
static void __init spectre_v2_select_mitigation(void)
{
enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
enum spectre_v2_mitigation mode = SPECTRE_V2_NONE;
/*
* If the CPU is not affected and the command line mode is NONE or AUTO
* then nothing to do.
*/
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
(cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO))
return;
switch (cmd) {
case SPECTRE_V2_CMD_NONE:
return;
case SPECTRE_V2_CMD_FORCE:
/* FALLTRHU */
case SPECTRE_V2_CMD_AUTO:
goto retpoline_auto;
case SPECTRE_V2_CMD_RETPOLINE_AMD:
if (IS_ENABLED(CONFIG_RETPOLINE))
goto retpoline_amd;
break;
case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
if (IS_ENABLED(CONFIG_RETPOLINE))
goto retpoline_generic;
break;
case SPECTRE_V2_CMD_RETPOLINE:
if (IS_ENABLED(CONFIG_RETPOLINE))
goto retpoline_auto;
break;
}
pr_err("kernel not compiled with retpoline; no mitigation available!");
return;
retpoline_auto:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
retpoline_amd:
if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
pr_err("LFENCE not serializing. Switching to generic retpoline\n");
goto retpoline_generic;
}
mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
} else {
retpoline_generic:
mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC :
SPECTRE_V2_RETPOLINE_MINIMAL;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
}
spectre_v2_enabled = mode;
pr_info("%s\n", spectre_v2_strings[mode]);
/*
* If neither SMEP or KPTI are available, there is a risk of
* hitting userspace addresses in the RSB after a context switch
* from a shallow call stack to a deeper one. To prevent this fill
* the entire RSB, even when using IBRS.
*
* Skylake era CPUs have a separate issue with *underflow* of the
* RSB, when they will predict 'ret' targets from the generic BTB.
* The proper mitigation for this is IBRS. If IBRS is not supported
* or deactivated in favour of retpolines the RSB fill on context
* switch is required.
*/
if ((!boot_cpu_has(X86_FEATURE_PTI) &&
!boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
pr_info("Filling RSB on context switch\n");
}
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 226 | 100.00% | 2 | 100.00% |
| Total | 226 | 100.00% | 2 | 100.00% |
#undef pr_fmt
#ifdef CONFIG_SYSFS
ssize_t cpu_show_meltdown(struct device *dev,
struct device_attribute *attr, char *buf)
{
if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
return sprintf(buf, "Not affected\n");
if (boot_cpu_has(X86_FEATURE_PTI))
return sprintf(buf, "Mitigation: PTI\n");
return sprintf(buf, "Vulnerable\n");
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Thomas Gleixner | 58 | 100.00% | 1 | 100.00% |
| Total | 58 | 100.00% | 1 | 100.00% |
ssize_t cpu_show_spectre_v1(struct device *dev,
struct device_attribute *attr, char *buf)
{
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
return sprintf(buf, "Not affected\n");
return sprintf(buf, "Vulnerable\n");
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Thomas Gleixner | 43 | 100.00% | 1 | 100.00% |
| Total | 43 | 100.00% | 1 | 100.00% |
ssize_t cpu_show_spectre_v2(struct device *dev,
struct device_attribute *attr, char *buf)
{
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
return sprintf(buf, "Not affected\n");
return sprintf(buf, "%s\n", spectre_v2_strings[spectre_v2_enabled]);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Thomas Gleixner | 42 | 87.50% | 1 | 50.00% |
| David Woodhouse | 6 | 12.50% | 1 | 50.00% |
| Total | 48 | 100.00% | 2 | 100.00% |
#endif
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| David Woodhouse | 700 | 70.49% | 2 | 13.33% |
| Thomas Gleixner | 151 | 15.21% | 1 | 6.67% |
| Jeremy Fitzhardinge | 70 | 7.05% | 1 | 6.67% |
| Borislav Petkov | 58 | 5.84% | 2 | 13.33% |
| Dave Jones | 4 | 0.40% | 2 | 13.33% |
| Josh Triplett | 3 | 0.30% | 1 | 6.67% |
| Suresh B. Siddha | 2 | 0.20% | 1 | 6.67% |
| Ingo Molnar | 2 | 0.20% | 2 | 13.33% |
| Greg Kroah-Hartman | 1 | 0.10% | 1 | 6.67% |
| Joe Perches | 1 | 0.10% | 1 | 6.67% |
| Laura Abbott | 1 | 0.10% | 1 | 6.67% |
| Total | 993 | 100.00% | 15 | 100.00% |
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.