arm64: extable: make fixup_exception() return bool

The return values of fixup_exception() and arm64_bpf_fixup_exception()
represent a boolean condition rather than an error code, so for clarity
it would be better to return `bool` rather than `int`.

This patch adjusts the code accordingly. While we're modifying the
prototype, we also remove the unnecessary `extern` keyword, so that this
won't look out of place when we make subsequent additions to the header.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: James Morse <james.morse@arm.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20211019160219.5202-9-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/extable.h

@@ -32,16 +32,16 @@ static inline bool in_bpf_jit(struct pt_regs *regs)
 }
 
 #ifdef CONFIG_BPF_JIT
-int arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
+bool arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
 			      struct pt_regs *regs);
 #else /* !CONFIG_BPF_JIT */
 static inline
-int arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
-			      struct pt_regs *regs)
+bool arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
+			       struct pt_regs *regs)
 {
-	return 0;
+	return false;
 }
 #endif /* !CONFIG_BPF_JIT */
 
-extern int fixup_exception(struct pt_regs *regs);
+bool fixup_exception(struct pt_regs *regs);
 #endif

arch/arm64/mm/extable.c

@@ -6,17 +6,17 @@
 #include <linux/extable.h>
 #include <linux/uaccess.h>
 
-int fixup_exception(struct pt_regs *regs)
+bool fixup_exception(struct pt_regs *regs)
 {
 	const struct exception_table_entry *fixup;
 
 	fixup = search_exception_tables(instruction_pointer(regs));
 	if (!fixup)
-		return 0;
+		return false;
 
 	if (in_bpf_jit(regs))
 		return arm64_bpf_fixup_exception(fixup, regs);
 
 	regs->pc = (unsigned long)&fixup->fixup + fixup->fixup;
-	return 1;
+	return true;
 }

arch/arm64/net/bpf_jit_comp.c

@@ -358,15 +358,15 @@ static void build_epilogue(struct jit_ctx *ctx)
 #define BPF_FIXUP_OFFSET_MASK	GENMASK(26, 0)
 #define BPF_FIXUP_REG_MASK	GENMASK(31, 27)
 
-int arm64_bpf_fixup_exception(const struct exception_table_entry *ex,
-			      struct pt_regs *regs)
+bool arm64_bpf_fixup_exception(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);
 
 	regs->regs[dst_reg] = 0;
 	regs->pc = (unsigned long)&ex->fixup - offset;
-	return 1;
+	return true;
 }
 
 /* For accesses to BTF pointers, add an entry to the exception table */