LoongArch: extable: Add `type` and `data` fields

This is a LoongArch port of commit d6e2cc564775 ("arm64: extable: add
`type` and `data` fields").

Subsequent patches will add specialized handlers for fixups, in addition
to the simple PC fixup we have today. In preparation, this patch adds a
new `type` field to struct exception_table_entry, and uses this to
distinguish the fixup and other cases. A `data` field is also added so
that subsequent patches can associate data specific to each exception
site (e.g. register numbers).

Handlers are named ex_handler_*() for consistency, following the example
of x86. At the same time, get_ex_fixup() is split out into a helper so
that it can be used by other ex_handler_*() functions in the subsequent
patches.

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

4 files changed, 29 insertions, 7 deletions

diff --git a/arch/loongarch/include/asm/asm-extable.h b/arch/loongarch/include/asm/asm-extable.h
index 74f8bc75472a..634bd770e3c4 100644
--- a/arch/loongarch/include/asm/asm-extable.h
+++ b/arch/loongarch/include/asm/asm-extable.h
@@ -2,17 +2,22 @@
 #ifndef __ASM_ASM_EXTABLE_H
 #define __ASM_ASM_EXTABLE_H
 
+#define EX_TYPE_NONE			0
+#define EX_TYPE_FIXUP			1
+
 #ifdef __ASSEMBLY__
 
-#define __ASM_EXTABLE_RAW(insn, fixup)			\
+#define __ASM_EXTABLE_RAW(insn, fixup, type, data)	\
 	.pushsection	__ex_table, "a";		\
 	.balign		4;				\
 	.long		((insn) - .);			\
 	.long		((fixup) - .);			\
+	.short		(type);				\
+	.short		(data);				\
 	.popsection;
 
 	.macro		_asm_extable, insn, fixup
-	__ASM_EXTABLE_RAW(\insn, \fixup)
+	__ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
 	.endm
 
 #else /* __ASSEMBLY__ */
@@ -20,15 +25,17 @@
 #include <linux/bits.h>
 #include <linux/stringify.h>
 
-#define __ASM_EXTABLE_RAW(insn, fixup)			\
+#define __ASM_EXTABLE_RAW(insn, fixup, type, data)	\
 	".pushsection	__ex_table, \"a\"\n"		\
 	".balign	4\n"				\
 	".long		((" insn ") - .)\n"		\
 	".long		((" fixup ") - .)\n"		\
+	".short		(" type ")\n"			\
+	".short		(" data ")\n"			\
 	".popsection\n"
 
 #define _ASM_EXTABLE(insn, fixup)	\
-	__ASM_EXTABLE_RAW(#insn, #fixup)
+	__ASM_EXTABLE_RAW(#insn, #fixup, __stringify(EX_TYPE_FIXUP), "0")
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/loongarch/include/asm/extable.h b/arch/loongarch/include/asm/extable.h
index b571c89705d1..92612b4364a1 100644
--- a/arch/loongarch/include/asm/extable.h
+++ b/arch/loongarch/include/asm/extable.h
@@ -17,10 +17,21 @@
 
 struct exception_table_entry {
 	int insn, fixup;
+	short type, data;
 };
 
 #define ARCH_HAS_RELATIVE_EXTABLE
 
+#define swap_ex_entry_fixup(a, b, tmp, delta)		\
+do {							\
+	(a)->fixup = (b)->fixup + (delta);		\
+	(b)->fixup = (tmp).fixup - (delta);		\
+	(a)->type = (b)->type;				\
+	(b)->type = (tmp).type;				\
+	(a)->data = (b)->data;				\
+	(b)->data = (tmp).data;				\
+} while (0)
+
 bool fixup_exception(struct pt_regs *regs);
 
 #endif
diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
index b3309a5e695b..efecda0c2361 100644
--- a/arch/loongarch/kernel/vmlinux.lds.S
+++ b/arch/loongarch/kernel/vmlinux.lds.S
@@ -4,6 +4,7 @@
 #include <asm/thread_info.h>
 
 #define PAGE_SIZE _PAGE_SIZE
+#define RO_EXCEPTION_TABLE_ALIGN	4
 
 /*
  * Put .bss..swapper_pg_dir as the first thing in .bss. This will
@@ -53,8 +54,6 @@ SECTIONS
 	. = ALIGN(PECOFF_SEGMENT_ALIGN);
 	_etext = .;
 
-	EXCEPTION_TABLE(16)
-
 	.got : ALIGN(16) { *(.got) }
 	.plt : ALIGN(16) { *(.plt) }
 	.got.plt : ALIGN(16) { *(.got.plt) }
diff --git a/arch/loongarch/mm/extable.c b/arch/loongarch/mm/extable.c
index 08a9a7d6357a..fd2395221cff 100644
--- a/arch/loongarch/mm/extable.c
+++ b/arch/loongarch/mm/extable.c
@@ -30,5 +30,10 @@ bool fixup_exception(struct pt_regs *regs)
 	if (!ex)
 		return false;
 
-	return ex_handler_fixup(ex, regs);
+	switch (ex->type) {
+	case EX_TYPE_FIXUP:
+		return ex_handler_fixup(ex, regs);
+	}
+
+	BUG();
 }