[PATCHV2 1/3] x86, ras: Add new infrastructure for machine check fixup tables

[Tony Luck <tony.luck@intel.com>]

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

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/Kconfig                  |  4 ++++
 arch/x86/include/asm/asm.h        | 10 ++++++++--
 arch/x86/include/asm/uaccess.h    |  8 ++++++++
 arch/x86/mm/extable.c             | 19 +++++++++++++++++++
 include/asm-generic/vmlinux.lds.h |  6 ++++++
 include/linux/module.h            |  1 +
 kernel/extable.c                  | 20 ++++++++++++++++++++
 7 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 96d058a87100..db5c6e1d6e37 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1001,6 +1001,10 @@ 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
+	depends on X86_MCE && X86_64
+	def_bool y
+
 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/uaccess.h b/arch/x86/include/asm/uaccess.h
index a8df874f3e88..7b02ca1991b4 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -111,6 +111,14 @@ struct exception_table_entry {
 #define ARCH_HAS_SEARCH_EXTABLE
 
 extern int fixup_exception(struct pt_regs *regs);
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+extern int fixup_mcexception(struct pt_regs *regs, u64 addr);
+#else
+static inline int fixup_mcexception(struct pt_regs *regs, u64 addr)
+{
+	return 0;
+}
+#endif
 extern int early_fixup_exception(unsigned long *ip);
 
 /*
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 903ec1e9c326..a461c4212758 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -49,6 +49,25 @@ int fixup_exception(struct pt_regs *regs)
 	return 0;
 }
 
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+int fixup_mcexception(struct pt_regs *regs, u64 addr)
+{
+	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;
+		regs->ax = BIT(63) | addr;
+		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..21bb20d1172a 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -473,6 +473,12 @@
 		VMLINUX_SYMBOL(__start___ex_table) = .;			\
 		*(__ex_table)						\
 		VMLINUX_SYMBOL(__stop___ex_table) = .;			\
+	}								\
+	. = ALIGN(align);						\
+	__mcex_table : AT(ADDR(__mcex_table) - LOAD_OFFSET) {		\
+		VMLINUX_SYMBOL(__start___mcex_table) = .;		\
+		*(__mcex_table)						\
+		VMLINUX_SYMBOL(__stop___mcex_table) = .;		\
 	}
 
 /*
diff --git a/include/linux/module.h b/include/linux/module.h
index 3a19c79918e0..ffecbfcc462c 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -270,6 +270,7 @@ extern const typeof(name) __mod_##type##__##name##_device_table		\
 
 /* Given an address, look for it in the exception tables */
 const struct exception_table_entry *search_exception_tables(unsigned long add);
+const struct exception_table_entry *search_mcexception_tables(unsigned long a);
 
 struct notifier_block;
 
diff --git a/kernel/extable.c b/kernel/extable.c
index e820ccee9846..7b224fbcb708 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -34,6 +34,10 @@ DEFINE_MUTEX(text_mutex);
 
 extern struct exception_table_entry __start___ex_table[];
 extern struct exception_table_entry __stop___ex_table[];
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+extern struct exception_table_entry __start___mcex_table[];
+extern struct exception_table_entry __stop___mcex_table[];
+#endif
 
 /* Cleared by build time tools if the table is already sorted. */
 u32 __initdata __visible main_extable_sort_needed = 1;
@@ -45,6 +49,10 @@ void __init sort_main_extable(void)
 		pr_notice("Sorting __ex_table...\n");
 		sort_extable(__start___ex_table, __stop___ex_table);
 	}
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+	if (__stop___mcex_table > __start___mcex_table)
+		sort_extable(__start___mcex_table, __stop___mcex_table);
+#endif
 }
 
 /* Given an address, look for it in the exception tables. */
@@ -58,6 +66,18 @@ const struct exception_table_entry *search_exception_tables(unsigned long addr)
 	return e;
 }
 
+#ifdef CONFIG_MCE_KERNEL_RECOVERY
+/* Given an address, look for it in the machine check exception tables. */
+const struct exception_table_entry *search_mcexception_tables(
+				    unsigned long addr)
+{
+	const struct exception_table_entry *e;
+
+	e = search_extable(__start___mcex_table, __stop___mcex_table-1, addr);
+	return e;
+}
+#endif
+
 static inline int init_kernel_text(unsigned long addr)
 {
 	if (addr >= (unsigned long)_sinittext &&
-- 
2.1.4

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