[PATCH 10/13] arm64: extable: add `type` and `data` fields
Will Deacon
will at kernel.org
Tue Oct 19 04:29:55 PDT 2021
On Wed, Oct 13, 2021 at 12:00:56PM +0100, Mark Rutland wrote:
> 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); \
Why are you reducing the alignment here?
> 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;
> + }
> +}
This is very nearly a direct copy of x86_sort_relative_table() (magic
numbers and all). It would be nice to tidy that up, but I couldn't
immediately see a good way to do it :(
Will
More information about the linux-arm-kernel
mailing list