[PATCHV3 1/3] x86, ras: Add new infrastructure for machine check fixup tables

From: Tony Luck
Date: Wed Dec 16 2015 - 12:21:48 EST

Copy the existing page fault fixup mechanisms to create a new table
to be used when fixing machine checks. Note:
1) At this time we only provide a macro to annotate assembly code
2) We assume all fixups will in code builtin to the kernel.
3) Only for x86_64
4) New code under CONFIG_MCE_KERNEL_RECOVERY (default 'n')

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
arch/x86/Kconfig | 10 ++++++++++
arch/x86/include/asm/asm.h | 10 ++++++++--
arch/x86/include/asm/mce.h | 14 ++++++++++++++
arch/x86/kernel/cpu/mcheck/mce.c | 16 ++++++++++++++++
arch/x86/kernel/vmlinux.lds.S | 6 +++++-
arch/x86/mm/extable.c | 19 +++++++++++++++++++
include/asm-generic/vmlinux.lds.h | 12 +++++++-----
7 files changed, 79 insertions(+), 8 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 96d058a87100..42d26b4d1ec4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1001,6 +1001,16 @@ config X86_MCE_INJECT
If you don't know what a machine check is and you don't do kernel
QA it is safe to say n.

+config MCE_KERNEL_RECOVERY
+ bool "Recovery from machine checks in special kernel memory copy functions"
+ default n
+ depends on X86_MCE && X86_64
+ ---help---
+ This option provides a new memory copy function mcsafe_memcpy()
+ that is annotated to allow the machine check handler to return
+ to an alternate code path to return an error to the caller instead
+ of crashing the system. Say yes if you have a driver that uses this.
+
config X86_THERMAL_VECTOR
def_bool y
depends on X86_MCE_INTEL
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 189679aba703..a5d483ac11fa 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -44,13 +44,19 @@

/* Exception table entry */
#ifdef __ASSEMBLY__
-# define _ASM_EXTABLE(from,to) \
- .pushsection "__ex_table","a" ; \
+# define __ASM_EXTABLE(from, to, table) \
+ .pushsection table, "a" ; \
.balign 8 ; \
.long (from) - . ; \
.long (to) - . ; \
.popsection

+# define _ASM_EXTABLE(from, to) \
+ __ASM_EXTABLE(from, to, "__ex_table")
+
+# define _ASM_MCEXTABLE(from, to) \
+ __ASM_EXTABLE(from, to, "__mcex_table")
+
# define _ASM_EXTABLE_EX(from,to) \
.pushsection "__ex_table","a" ; \
.balign 8 ; \
diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 2dbc0bf2b9f3..9dc11d2a9db1 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -279,4 +279,18 @@ struct cper_sec_mem_err;
extern void apei_mce_report_mem_error(int corrected,
struct cper_sec_mem_err *mem_err);

+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+const struct exception_table_entry *search_mcexception_tables(unsigned long a);
+int fixup_mcexception(struct pt_regs *regs);
+#else
+static inline const struct exception_table_entry *search_mcexception_tables(unsigned long a)
+{
+ return 0;
+}
+static inline int fixup_mcexception(struct pt_regs *regs)
+{
+ return 0;
+}
+#endif
+
#endif /* _ASM_X86_MCE_H */
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 9d014b82a124..0111cd49ee94 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -31,6 +31,7 @@
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/init.h>
+#include <linux/module.h>
#include <linux/kmod.h>
#include <linux/poll.h>
#include <linux/nmi.h>
@@ -2022,8 +2023,23 @@ static int __init mcheck_enable(char *str)
}
__setup("mce", mcheck_enable);

+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+extern struct exception_table_entry __start___mcex_table[];
+extern struct exception_table_entry __stop___mcex_table[];
+
+/* Given an address, look for it in the machine check exception tables. */
+const struct exception_table_entry *search_mcexception_tables(unsigned long addr)
+{
+ return search_extable(__start___mcex_table, __stop___mcex_table-1, addr);
+}
+#endif
+
int __init mcheck_init(void)
{
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+ if (__stop___mcex_table > __start___mcex_table)
+ sort_extable(__start___mcex_table, __stop___mcex_table);
+#endif
mcheck_intel_therm_init();
mce_register_decode_chain(&mce_srao_nb);
mcheck_vendor_init_severity();
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 74e4bf11f562..a65fa0deda06 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -110,7 +110,11 @@ SECTIONS

NOTES :text :note

- EXCEPTION_TABLE(16) :text = 0x9090
+ EXCEPTION_TABLE(16)
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+ NAMED_EXCEPTION_TABLE(16, mcex)
+#endif
+ :text = 0x9090

#if defined(CONFIG_DEBUG_RODATA)
/* .text should occupy whole number of pages */
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 903ec1e9c326..f8f8b72e88af 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -2,6 +2,7 @@
#include <linux/spinlock.h>
#include <linux/sort.h>
#include <asm/uaccess.h>
+#include <asm/mce.h>

static inline unsigned long
ex_insn_addr(const struct exception_table_entry *x)
@@ -49,6 +50,24 @@ int fixup_exception(struct pt_regs *regs)
return 0;
}

+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+int fixup_mcexception(struct pt_regs *regs)
+{
+ const struct exception_table_entry *fixup;
+ unsigned long new_ip;
+
+ fixup = search_mcexception_tables(regs->ip);
+ if (fixup) {
+ new_ip = ex_fixup_addr(fixup);
+
+ regs->ip = new_ip;
+ return 1;
+ }
+
+ return 0;
+}
+#endif
+
/* Restricted version used during very early boot */
int __init early_fixup_exception(unsigned long *ip)
{
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 1781e54ea6d3..42ef98de373a 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -467,14 +467,16 @@
/*
* Exception table
*/
-#define EXCEPTION_TABLE(align) \
+#define NAMED_EXCEPTION_TABLE(align, pfx) \
. = ALIGN(align); \
- __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \
- VMLINUX_SYMBOL(__start___ex_table) = .; \
- *(__ex_table) \
- VMLINUX_SYMBOL(__stop___ex_table) = .; \
+ __##pfx##_table : AT(ADDR(__##pfx##_table) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start___##pfx##_table) = .; \
+ *(__##pfx##_table) \
+ VMLINUX_SYMBOL(__stop___##pfx##_table) = .; \
}

+#define EXCEPTION_TABLE(align) NAMED_EXCEPTION_TABLE(align, ex)
+
/*
* Init task
*/
--
2.1.4

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