[PATCH 10/13] arm64: extable: add `type` and `data` fields
Mark Rutland
mark.rutland at arm.com
Wed Oct 13 04:00:56 PDT 2021
Subsequent patches will add specialized handlers for fixups, in addition
to the simple PC fixup and BPF handlers 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 BPF 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 exmaple
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 ins subsequent
patches.
This patch will increase the size of the exception tables, which will be
remedied by subsequent patches removing redundant fixup code. There
should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Alexei Starovoitov <ast at kernel.org>
Cc: Andrii Nakryiko <andrii at kernel.org>
Cc: Ard Biesheuvel <ardb at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Daniel Borkmann <daniel at iogearbox.net>
Cc: James Morse <james.morse at arm.com>
Cc: Jean-Philippe Brucker <jean-philippe at linaro.org>
Cc: Robin Murphy <robin.murphy at arm.com>
Cc: Will Deacon <will at kernel.org>
---
arch/arm64/include/asm/asm-extable.h | 32 ++++++++++++++++++++------------
arch/arm64/include/asm/extable.h | 19 +++++++++++++++----
arch/arm64/mm/extable.c | 29 +++++++++++++++++++++++++----
arch/arm64/net/bpf_jit_comp.c | 7 +++++--
scripts/sorttable.c | 30 ++++++++++++++++++++++++++++++
5 files changed, 95 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
index 986b4c0d4792..5ee748edaef1 100644
--- a/arch/arm64/include/asm/asm-extable.h
+++ b/arch/arm64/include/asm/asm-extable.h
@@ -2,13 +2,19 @@
#ifndef __ASM_ASM_EXTABLE_H
#define __ASM_ASM_EXTABLE_H
+#define EX_TYPE_NONE 0
+#define EX_TYPE_FIXUP 1
+#define EX_TYPE_BPF 2
+
#ifdef __ASSEMBLY__
-#define __ASM_EXTABLE_RAW(insn, fixup) \
- .pushsection __ex_table, "a"; \
- .align 3; \
- .long ((insn) - .); \
- .long ((fixup) - .); \
+#define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
+ .pushsection __ex_table, "a"; \
+ .align 2; \
+ .long ((insn) - .); \
+ .long ((fixup) - .); \
+ .short (type); \
+ .short (data); \
.popsection;
/*
@@ -16,7 +22,7 @@
* when an unhandled fault is taken.
*/
.macro _asm_extable, insn, fixup
- __ASM_EXTABLE_RAW(\insn, \fixup)
+ __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
.endm
/*
@@ -33,15 +39,17 @@
#include <linux/stringify.h>
-#define __ASM_EXTABLE_RAW(insn, fixup) \
- ".pushsection __ex_table, \"a\"\n" \
- ".align 3\n" \
- ".long ((" insn ") - .)\n" \
- ".long ((" fixup ") - .)\n" \
+#define __ASM_EXTABLE_RAW(insn, fixup, type, data) \
+ ".pushsection __ex_table, \"a\"\n" \
+ ".align 2\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/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h
index 1859b9fd566f..8b300dd28def 100644
--- a/arch/arm64/include/asm/extable.h
+++ b/arch/arm64/include/asm/extable.h
@@ -18,10 +18,21 @@
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)
+
static inline bool in_bpf_jit(struct pt_regs *regs)
{
if (!IS_ENABLED(CONFIG_BPF_JIT))
@@ -32,12 +43,12 @@ static inline bool in_bpf_jit(struct pt_regs *regs)
}
#ifdef CONFIG_BPF_JIT
-bool arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
- struct pt_regs *regs);
+bool ex_handler_bpf(const struct exception_table_entry *ex,
+ struct pt_regs *regs);
#else /* !CONFIG_BPF_JIT */
static inline
-bool arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
- struct pt_regs *regs)
+bool ex_handler_bpf(const struct exception_table_entry *ex,
+ struct pt_regs *regs)
{
return false;
}
diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
index dba3d59f3eca..c2951b963335 100644
--- a/arch/arm64/mm/extable.c
+++ b/arch/arm64/mm/extable.c
@@ -6,6 +6,24 @@
#include <linux/extable.h>
#include <linux/uaccess.h>
+#include <asm/asm-extable.h>
+
+typedef bool (*ex_handler_t)(const struct exception_table_entry *,
+ struct pt_regs *);
+
+static inline unsigned long
+get_ex_fixup(const struct exception_table_entry *ex)
+{
+ return ((unsigned long)&ex->fixup + ex->fixup);
+}
+
+static bool ex_handler_fixup(const struct exception_table_entry *ex,
+ struct pt_regs *regs)
+{
+ regs->pc = get_ex_fixup(ex);
+ return true;
+}
+
bool fixup_exception(struct pt_regs *regs)
{
const struct exception_table_entry *ex;
@@ -14,9 +32,12 @@ bool fixup_exception(struct pt_regs *regs)
if (!ex)
return false;
- if (in_bpf_jit(regs))
- return arm64_bpf_fixup_exception(ex, regs);
+ switch (ex->type) {
+ case EX_TYPE_FIXUP:
+ return ex_handler_fixup(ex, regs);
+ case EX_TYPE_BPF:
+ return ex_handler_bpf(ex, regs);
+ }
- regs->pc = (unsigned long)&ex->fixup + ex->fixup;
- return true;
+ BUG();
}
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 956c841ef346..7df7345e60d8 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -13,6 +13,7 @@
#include <linux/printk.h>
#include <linux/slab.h>
+#include <asm/asm-extable.h>
#include <asm/byteorder.h>
#include <asm/cacheflush.h>
#include <asm/debug-monitors.h>
@@ -358,8 +359,8 @@ static void build_epilogue(struct jit_ctx *ctx)
#define BPF_FIXUP_OFFSET_MASK GENMASK(26, 0)
#define BPF_FIXUP_REG_MASK GENMASK(31, 27)
-bool arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
- struct pt_regs *regs)
+bool ex_handler_bpf(const struct exception_table_entry *ex,
+ struct pt_regs *regs)
{
off_t offset = FIELD_GET(BPF_FIXUP_OFFSET_MASK, ex->fixup);
int dst_reg = FIELD_GET(BPF_FIXUP_REG_MASK, ex->fixup);
@@ -412,6 +413,8 @@ static int add_exception_handler(const struct bpf_insn *insn,
ex->fixup = FIELD_PREP(BPF_FIXUP_OFFSET_MASK, offset) |
FIELD_PREP(BPF_FIXUP_REG_MASK, dst_reg);
+ ex->type = EX_TYPE_BPF;
+
ctx->exentry_idx++;
return 0;
}
diff --git a/scripts/sorttable.c b/scripts/sorttable.c
index 6ee4fa882919..ee95bb47a50d 100644
--- a/scripts/sorttable.c
+++ b/scripts/sorttable.c
@@ -231,6 +231,34 @@ static void sort_relative_table(char *extab_image, int image_size)
}
}
+static void arm64_sort_relative_table(char *extab_image, int image_size)
+{
+ int i = 0;
+
+ while (i < image_size) {
+ uint32_t *loc = (uint32_t *)(extab_image + i);
+
+ w(r(loc) + i, loc);
+ w(r(loc + 1) + i + 4, loc + 1);
+ /* Don't touch the fixup type or data */
+
+ i += sizeof(uint32_t) * 3;
+ }
+
+ qsort(extab_image, image_size / 12, 12, compare_relative_table);
+
+ i = 0;
+ while (i < image_size) {
+ uint32_t *loc = (uint32_t *)(extab_image + i);
+
+ w(r(loc) - i, loc);
+ w(r(loc + 1) - (i + 4), loc + 1);
+ /* Don't touch the fixup type or data */
+
+ i += sizeof(uint32_t) * 3;
+ }
+}
+
static void x86_sort_relative_table(char *extab_image, int image_size)
{
int i = 0;
@@ -343,6 +371,8 @@ static int do_file(char const *const fname, void *addr)
custom_sort = s390_sort_relative_table;
break;
case EM_AARCH64:
+ custom_sort = arm64_sort_relative_table;
+ break;
case EM_PARISC:
case EM_PPC:
case EM_PPC64:
--
2.11.0
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