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authorYouling Tang <tangyouling@loongson.cn>2022-12-10 22:39:48 +0800
committerHuacai Chen <chenhuacai@loongson.cn>2022-12-14 08:36:11 +0800
commit3d36f4298ba91fbdec6bc56aa7bb0663cba6ab0c (patch)
tree18b04c43e9acae25114c33a45814ae1233a09955
parent508f28c67171e276356650f407dd87d42b6913ef (diff)
LoongArch: Switch to relative exception tables
Similar to other architectures such as arm64, x86, riscv and so on, use offsets relative to the exception table entry values rather than their absolute addresses for both the exception location and the fixup. However, LoongArch label difference because it will actually produce two relocations, a pair of R_LARCH_ADD32 and R_LARCH_SUB32. Take simple code below for example: $ cat test_ex_table.S .section .text 1: nop .section __ex_table,"a" .balign 4 .long (1b - .) .previous $ loongarch64-unknown-linux-gnu-gcc -c test_ex_table.S $ loongarch64-unknown-linux-gnu-readelf -Wr test_ex_table.o Relocation section '.rela__ex_table' at offset 0x100 contains 2 entries: Offset Info Type Symbol's Value Symbol's Name + Addend 0000000000000000 0000000600000032 R_LARCH_ADD32 0000000000000000 .L1^B1 + 0 0000000000000000 0000000500000037 R_LARCH_SUB32 0000000000000000 L0^A + 0 The modpost will complain the R_LARCH_SUB32 relocation, so we need to patch modpost.c to skip this relocation for .rela__ex_table section. Signed-off-by: Youling Tang <tangyouling@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
-rw-r--r--arch/loongarch/include/asm/asm-extable.h12
-rw-r--r--arch/loongarch/include/asm/extable.h26
-rw-r--r--arch/loongarch/include/asm/uaccess.h2
-rw-r--r--arch/loongarch/mm/extable.c32
-rw-r--r--scripts/mod/modpost.c13
-rw-r--r--scripts/sorttable.c2
6 files changed, 69 insertions, 18 deletions
diff --git a/arch/loongarch/include/asm/asm-extable.h b/arch/loongarch/include/asm/asm-extable.h
index 4f615bf56727..74f8bc75472a 100644
--- a/arch/loongarch/include/asm/asm-extable.h
+++ b/arch/loongarch/include/asm/asm-extable.h
@@ -6,9 +6,9 @@
#define __ASM_EXTABLE_RAW(insn, fixup) \
.pushsection __ex_table, "a"; \
- .balign 8; \
- .quad (insn); \
- .quad (fixup); \
+ .balign 4; \
+ .long ((insn) - .); \
+ .long ((fixup) - .); \
.popsection;
.macro _asm_extable, insn, fixup
@@ -22,9 +22,9 @@
#define __ASM_EXTABLE_RAW(insn, fixup) \
".pushsection __ex_table, \"a\"\n" \
- ".balign 8\n" \
- ".quad ((" insn "))\n" \
- ".quad ((" fixup "))\n" \
+ ".balign 4\n" \
+ ".long ((" insn ") - .)\n" \
+ ".long ((" fixup ") - .)\n" \
".popsection\n"
#define _ASM_EXTABLE(insn, fixup) \
diff --git a/arch/loongarch/include/asm/extable.h b/arch/loongarch/include/asm/extable.h
new file mode 100644
index 000000000000..b571c89705d1
--- /dev/null
+++ b/arch/loongarch/include/asm/extable.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_LOONGARCH_EXTABLE_H
+#define _ASM_LOONGARCH_EXTABLE_H
+
+/*
+ * The exception table consists of pairs of relative offsets: the first
+ * is the relative offset to an instruction that is allowed to fault,
+ * and the second is the relative offset at which the program should
+ * continue. No registers are modified, so it is entirely up to the
+ * continuation code to figure out what to do.
+ *
+ * All the routines below use bits of fixup code that are out of line
+ * with the main instruction path. This means when everything is well,
+ * we don't even have to jump over them. Further, they do not intrude
+ * on our cache or tlb entries.
+ */
+
+struct exception_table_entry {
+ int insn, fixup;
+};
+
+#define ARCH_HAS_RELATIVE_EXTABLE
+
+bool fixup_exception(struct pt_regs *regs);
+
+#endif
diff --git a/arch/loongarch/include/asm/uaccess.h b/arch/loongarch/include/asm/uaccess.h
index bf9a4e218ac0..e33282e0bdef 100644
--- a/arch/loongarch/include/asm/uaccess.h
+++ b/arch/loongarch/include/asm/uaccess.h
@@ -15,8 +15,8 @@
#include <linux/string.h>
#include <linux/extable.h>
#include <asm/pgtable.h>
+#include <asm/extable.h>
#include <asm/asm-extable.h>
-#include <asm-generic/extable.h>
#include <asm-generic/access_ok.h>
extern u64 __ua_limit;
diff --git a/arch/loongarch/mm/extable.c b/arch/loongarch/mm/extable.c
index bc20988f2b87..08a9a7d6357a 100644
--- a/arch/loongarch/mm/extable.c
+++ b/arch/loongarch/mm/extable.c
@@ -3,20 +3,32 @@
* Copyright (C) 2020-2022 Loongson Technology Corporation Limited
*/
#include <linux/extable.h>
-#include <linux/spinlock.h>
-#include <asm/branch.h>
#include <linux/uaccess.h>
+#include <asm/asm-extable.h>
+#include <asm/branch.h>
+
+static inline unsigned long
+get_ex_fixup(const struct exception_table_entry *ex)
+{
+ return ((unsigned long)&ex->fixup + ex->fixup);
+}
-int fixup_exception(struct pt_regs *regs)
+static bool ex_handler_fixup(const struct exception_table_entry *ex,
+ struct pt_regs *regs)
{
- const struct exception_table_entry *fixup;
+ regs->csr_era = get_ex_fixup(ex);
- fixup = search_exception_tables(exception_era(regs));
- if (fixup) {
- regs->csr_era = fixup->fixup;
+ return true;
+}
+
+
+bool fixup_exception(struct pt_regs *regs)
+{
+ const struct exception_table_entry *ex;
- return 1;
- }
+ ex = search_exception_tables(exception_era(regs));
+ if (!ex)
+ return false;
- return 0;
+ return ex_handler_fixup(ex, regs);
}
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 2c80da0220c3..9321c0a05ffd 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1523,6 +1523,14 @@ static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
#define R_RISCV_SUB32 39
#endif
+#ifndef EM_LOONGARCH
+#define EM_LOONGARCH 258
+#endif
+
+#ifndef R_LARCH_SUB32
+#define R_LARCH_SUB32 55
+#endif
+
static void section_rela(const char *modname, struct elf_info *elf,
Elf_Shdr *sechdr)
{
@@ -1564,6 +1572,11 @@ static void section_rela(const char *modname, struct elf_info *elf,
ELF_R_TYPE(r.r_info) == R_RISCV_SUB32)
continue;
break;
+ case EM_LOONGARCH:
+ if (!strcmp("__ex_table", fromsec) &&
+ ELF_R_TYPE(r.r_info) == R_LARCH_SUB32)
+ continue;
+ break;
}
sym = elf->symtab_start + r_sym;
/* Skip special sections */
diff --git a/scripts/sorttable.c b/scripts/sorttable.c
index fba40e99f354..0f2beda80478 100644
--- a/scripts/sorttable.c
+++ b/scripts/sorttable.c
@@ -312,12 +312,12 @@ static int do_file(char const *const fname, void *addr)
case EM_PARISC:
case EM_PPC:
case EM_PPC64:
+ case EM_LOONGARCH:
custom_sort = sort_relative_table;
break;
case EM_ARCOMPACT:
case EM_ARCV2:
case EM_ARM:
- case EM_LOONGARCH:
case EM_MICROBLAZE:
case EM_MIPS:
case EM_XTENSA: