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// SPDX-License-Identifier: GPL-2.0-only
/*
* MCE grading rules.
* Copyright 2008, 2009 Intel Corporation.
*
* Author: Andi Kleen
*/
#include <linux/kernel.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <asm/mce.h>
#include <asm/intel-family.h>
#include <asm/traps.h>
#include <asm/insn.h>
#include <asm/insn-eval.h>
#include "internal.h"
/*
* Grade an mce by severity. In general the most severe ones are processed
* first. Since there are quite a lot of combinations test the bits in a
* table-driven way. The rules are simply processed in order, first
* match wins.
*
* Note this is only used for machine check exceptions, the corrected
* errors use much simpler rules. The exceptions still check for the corrected
* errors, but only to leave them alone for the CMCI handler (except for
* panic situations)
*/
enum context { IN_KERNEL = 1, IN_USER = 2, IN_KERNEL_RECOV = 3 };
enum ser { SER_REQUIRED = 1, NO_SER = 2 };
enum exception { EXCP_CONTEXT = 1, NO_EXCP = 2 };
static struct severity {
u64 mask;
u64 result;
unsigned char sev;
unsigned char mcgmask;
unsigned char mcgres;
unsigned char ser;
unsigned char context;
unsigned char excp;
unsigned char covered;
unsigned char cpu_model;
unsigned char cpu_minstepping;
unsigned char bank_lo, bank_hi;
char *msg;
} severities[] = {
#define MCESEV(s, m, c...) { .sev = MCE_ ## s ## _SEVERITY, .msg = m, ## c }
#define BANK_RANGE(l, h) .bank_lo = l, .bank_hi = h
#define MODEL_STEPPING(m, s) .cpu_model = m, .cpu_minstepping = s
#define KERNEL .context = IN_KERNEL
#define USER .context = IN_USER
#define KERNEL_RECOV .context = IN_KERNEL_RECOV
#define SER .ser = SER_REQUIRED
#define NOSER .ser = NO_SER
#define EXCP .excp = EXCP_CONTEXT
#define NOEXCP .excp = NO_EXCP
#define BITCLR(x) .mask = x, .result = 0
#define BITSET(x) .mask = x, .result = x
#define MCGMASK(x, y) .mcgmask = x, .mcgres = y
#define MASK(x, y) .mask = x, .result = y
#define MCI_UC_S (MCI_STATUS_UC|MCI_STATUS_S)
#define MCI_UC_AR (MCI_STATUS_UC|MCI_STATUS_AR)
#define MCI_UC_SAR (MCI_STATUS_UC|MCI_STATUS_S|MCI_STATUS_AR)
#define MCI_ADDR (MCI_STATUS_ADDRV|MCI_STATUS_MISCV)
MCESEV(
NO, "Invalid",
BITCLR(MCI_STATUS_VAL)
),
MCESEV(
NO, "Not enabled",
EXCP, BITCLR(MCI_STATUS_EN)
),
MCESEV(
PANIC, "Processor context corrupt",
BITSET(MCI_STATUS_PCC)
),
/* When MCIP is not set something is very confused */
MCESEV(
PANIC, "MCIP not set in MCA handler",
EXCP, MCGMASK(MCG_STATUS_MCIP, 0)
),
/* Neither return not error IP -- no chance to recover -> PANIC */
MCESEV(
PANIC, "Neither restart nor error IP",
EXCP, MCGMASK(MCG_STATUS_RIPV|MCG_STATUS_EIPV, 0)
),
MCESEV(
PANIC, "In kernel and no restart IP",
EXCP, KERNEL, MCGMASK(MCG_STATUS_RIPV, 0)
),
MCESEV(
PANIC, "In kernel and no restart IP",
EXCP, KERNEL_RECOV, MCGMASK(MCG_STATUS_RIPV, 0)
),
MCESEV(
KEEP, "Corrected error",
NOSER, BITCLR(MCI_STATUS_UC)
),
/*
* known AO MCACODs reported via MCE or CMC:
*
* SRAO could be signaled either via a machine check exception or
* CMCI with the corresponding bit S 1 or 0. So we don't need to
* check bit S for SRAO.
*/
MCESEV(
AO, "Action optional: memory scrubbing error",
SER, MASK(MCI_UC_AR|MCACOD_SCRUBMSK, MCI_STATUS_UC|MCACOD_SCRUB)
),
MCESEV(
AO, "Action optional: last level cache writeback error",
SER, MASK(MCI_UC_AR|MCACOD, MCI_STATUS_UC|MCACOD_L3WB)
),
/*
* Quirk for Skylake/Cascade Lake. Patrol scrubber may be configured
* to report uncorrected errors using CMCI with a special signature.
* UC=0, MSCOD=0x0010, MCACOD=binary(000X 0000 1100 XXXX) reported
* in one of the memory controller banks.
* Set severity to "AO" for same action as normal patrol scrub error.
*/
MCESEV(
AO, "Uncorrected Patrol Scrub Error",
SER, MASK(MCI_STATUS_UC|MCI_ADDR|0xffffeff0, MCI_ADDR|0x001000c0),
MODEL_STEPPING(INTEL_FAM6_SKYLAKE_X, 4), BANK_RANGE(13, 18)
),
/* ignore OVER for UCNA */
MCESEV(
UCNA, "Uncorrected no action required",
SER, MASK(MCI_UC_SAR, MCI_STATUS_UC)
),
MCESEV(
PANIC, "Illegal combination (UCNA with AR=1)",
SER,
MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_STATUS_UC|MCI_STATUS_AR)
),
MCESEV(
KEEP, "Non signaled machine check",
SER, BITCLR(MCI_STATUS_S)
),
MCESEV(
PANIC, "Action required with lost events",
SER, BITSET(MCI_STATUS_OVER|MCI_UC_SAR)
),
/* known AR MCACODs: */
#ifdef CONFIG_MEMORY_FAILURE
MCESEV(
KEEP, "Action required but unaffected thread is continuable",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR, MCI_UC_SAR|MCI_ADDR),
MCGMASK(MCG_STATUS_RIPV|MCG_STATUS_EIPV, MCG_STATUS_RIPV)
),
MCESEV(
AR, "Action required: data load in error recoverable area of kernel",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),
KERNEL_RECOV
),
MCESEV(
AR, "Action required: data load error in a user process",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),
USER
),
MCESEV(
AR, "Action required: instruction fetch error in a user process",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_INSTR),
USER
),
MCESEV(
PANIC, "Data load in unrecoverable area of kernel",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),
KERNEL
),
MCESEV(
PANIC, "Instruction fetch error in kernel",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_INSTR),
KERNEL
),
#endif
MCESEV(
PANIC, "Action required: unknown MCACOD",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_UC_SAR)
),
MCESEV(
SOME, "Action optional: unknown MCACOD",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_UC_S)
),
MCESEV(
SOME, "Action optional with lost events",
SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR, MCI_STATUS_OVER|MCI_UC_S)
),
MCESEV(
PANIC, "Overflowed uncorrected",
BITSET(MCI_STATUS_OVER|MCI_STATUS_UC)
),
MCESEV(
UC, "Uncorrected",
BITSET(MCI_STATUS_UC)
),
MCESEV(
SOME, "No match",
BITSET(0)
) /* always matches. keep at end */
};
#define mc_recoverable(mcg) (((mcg) & (MCG_STATUS_RIPV|MCG_STATUS_EIPV)) == \
(MCG_STATUS_RIPV|MCG_STATUS_EIPV))
static bool is_copy_from_user(struct pt_regs *regs)
{
u8 insn_buf[MAX_INSN_SIZE];
unsigned long addr;
struct insn insn;
int ret;
if (!regs)
return false;
if (copy_from_kernel_nofault(insn_buf, (void *)regs->ip, MAX_INSN_SIZE))
return false;
ret = insn_decode_kernel(&insn, insn_buf);
if (ret < 0)
return false;
switch (insn.opcode.value) {
/* MOV mem,reg */
case 0x8A: case 0x8B:
/* MOVZ mem,reg */
case 0xB60F: case 0xB70F:
addr = (unsigned long)insn_get_addr_ref(&insn, regs);
break;
/* REP MOVS */
case 0xA4: case 0xA5:
addr = regs->si;
break;
default:
return false;
}
if (fault_in_kernel_space(addr))
return false;
current->mce_vaddr = (void __user *)addr;
return true;
}
/*
* If mcgstatus indicated that ip/cs on the stack were
* no good, then "m->cs" will be zero and we will have
* to assume the worst case (IN_KERNEL) as we actually
* have no idea what we were executing when the machine
* check hit.
* If we do have a good "m->cs" (or a faked one in the
* case we were executing in VM86 mode) we can use it to
* distinguish an exception taken in user from from one
* taken in the kernel.
*/
static noinstr int error_context(struct mce *m, struct pt_regs *regs)
{
int fixup_type;
bool copy_user;
if ((m->cs & 3) == 3)
return IN_USER;
if (!mc_recoverable(m->mcgstatus))
return IN_KERNEL;
/* Allow instrumentation around external facilities usage. */
instrumentation_begin();
fixup_type = ex_get_fixup_type(m->ip);
copy_user = is_copy_from_user(regs);
instrumentation_end();
switch (fixup_type) {
case EX_TYPE_UACCESS:
case EX_TYPE_COPY:
if (!copy_user)
return IN_KERNEL;
m->kflags |= MCE_IN_KERNEL_COPYIN;
fallthrough;
case EX_TYPE_FAULT_MCE_SAFE:
case EX_TYPE_DEFAULT_MCE_SAFE:
m->kflags |= MCE_IN_KERNEL_RECOV;
return IN_KERNEL_RECOV;
default:
return IN_KERNEL;
}
}
/* See AMD PPR(s) section Machine Check Error Handling. */
static noinstr int mce_severity_amd(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)
{
char *panic_msg = NULL;
int ret;
/*
* Default return value: Action required, the error must be handled
* immediately.
*/
ret = MCE_AR_SEVERITY;
/* Processor Context Corrupt, no need to fumble too much, die! */
if (m->status & MCI_STATUS_PCC) {
panic_msg = "Processor Context Corrupt";
ret = MCE_PANIC_SEVERITY;
goto out;
}
if (m->status & MCI_STATUS_DEFERRED) {
ret = MCE_DEFERRED_SEVERITY;
goto out;
}
/*
* If the UC bit is not set, the system either corrected or deferred
* the error. No action will be required after logging the error.
*/
if (!(m->status & MCI_STATUS_UC)) {
ret = MCE_KEEP_SEVERITY;
goto out;
}
/*
* On MCA overflow, without the MCA overflow recovery feature the
* system will not be able to recover, panic.
*/
if ((m->status & MCI_STATUS_OVER) && !mce_flags.overflow_recov) {
panic_msg = "Overflowed uncorrected error without MCA Overflow Recovery";
ret = MCE_PANIC_SEVERITY;
goto out;
}
if (!mce_flags.succor) {
panic_msg = "Uncorrected error without MCA Recovery";
ret = MCE_PANIC_SEVERITY;
goto out;
}
if (error_context(m, regs) == IN_KERNEL) {
panic_msg = "Uncorrected unrecoverable error in kernel context";
ret = MCE_PANIC_SEVERITY;
}
out:
if (msg && panic_msg)
*msg = panic_msg;
return ret;
}
static noinstr int mce_severity_intel(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)
{
enum exception excp = (is_excp ? EXCP_CONTEXT : NO_EXCP);
enum context ctx = error_context(m, regs);
struct severity *s;
for (s = severities;; s++) {
if ((m->status & s->mask) != s->result)
continue;
if ((m->mcgstatus & s->mcgmask) != s->mcgres)
continue;
if (s->ser == SER_REQUIRED && !mca_cfg.ser)
continue;
if (s->ser == NO_SER && mca_cfg.ser)
continue;
if (s->context && ctx != s->context)
continue;
if (s->excp && excp != s->excp)
continue;
if (s->cpu_model && boot_cpu_data.x86_model != s->cpu_model)
continue;
if (s->cpu_minstepping && boot_cpu_data.x86_stepping < s->cpu_minstepping)
continue;
if (s->bank_lo && (m->bank < s->bank_lo || m->bank > s->bank_hi))
continue;
if (msg)
*msg = s->msg;
s->covered = 1;
if (s->sev >= MCE_UC_SEVERITY && ctx == IN_KERNEL)
return MCE_PANIC_SEVERITY;
return s->sev;
}
}
int noinstr mce_severity(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)
{
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
return mce_severity_amd(m, regs, msg, is_excp);
else
return mce_severity_intel(m, regs, msg, is_excp);
}
#ifdef CONFIG_DEBUG_FS
static void *s_start(struct seq_file *f, loff_t *pos)
{
if (*pos >= ARRAY_SIZE(severities))
return NULL;
return &severities[*pos];
}
static void *s_next(struct seq_file *f, void *data, loff_t *pos)
{
if (++(*pos) >= ARRAY_SIZE(severities))
return NULL;
return &severities[*pos];
}
static void s_stop(struct seq_file *f, void *data)
{
}
static int s_show(struct seq_file *f, void *data)
{
struct severity *ser = data;
seq_printf(f, "%d\t%s\n", ser->covered, ser->msg);
return 0;
}
static const struct seq_operations severities_seq_ops = {
.start = s_start,
.next = s_next,
.stop = s_stop,
.show = s_show,
};
static int severities_coverage_open(struct inode *inode, struct file *file)
{
return seq_open(file, &severities_seq_ops);
}
static ssize_t severities_coverage_write(struct file *file,
const char __user *ubuf,
size_t count, loff_t *ppos)
{
int i;
for (i = 0; i < ARRAY_SIZE(severities); i++)
severities[i].covered = 0;
return count;
}
static const struct file_operations severities_coverage_fops = {
.open = severities_coverage_open,
.release = seq_release,
.read = seq_read,
.write = severities_coverage_write,
.llseek = seq_lseek,
};
static int __init severities_debugfs_init(void)
{
struct dentry *dmce;
dmce = mce_get_debugfs_dir();
debugfs_create_file("severities-coverage", 0444, dmce, NULL,
&severities_coverage_fops);
return 0;
}
late_initcall(severities_debugfs_init);
#endif /* CONFIG_DEBUG_FS */