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Message-ID: <fdf9c1a8-f5a7-3fae-1743-fa95fe41be42@flygoat.com>
Date: Mon, 18 Jan 2021 09:49:31 +0800
From: Jiaxun Yang <jiaxun.yang@...goat.com>
To: Alexander Lobakin <alobakin@...me>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: Nathan Chancellor <natechancellor@...il.com>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Kees Cook <keescook@...omium.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Rapoport <rppt@...nel.org>,
Jinyang He <hejinyang@...ngson.cn>, linux-mips@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH mips-next 1/2] MIPS: module: optimize module relocations
processing
在 2021/1/16 下午11:02, Alexander Lobakin 写道:
> For now, module relocation functions are implemented as an array
> of handlers of type reloc_handler_t.
>
> Convert that array into a single switch-case function to:
> - remove unused arguments;
> - change the return type of simple handlers to void;
> - remove the array and don't use any data at all;
> - avoid using indirect calls;
> - allow the compiler to inline and greatly optimize
> the relocation function[s].
>
> The result on MIPS32 R2 with GCC 10.2 -O2 is:
>
> scripts/bloat-o-meter -c arch/mips/kernel/__module.o arch/mips/kernel/module.o
> add/remove: 1/11 grow/shrink: 1/0 up/down: 876/-1436 (-560)
> Function old new delta
> apply_relocate 456 1148 +692
> apply_r_mips_pc - 184 +184
> apply_r_mips_none 8 - -8
> apply_r_mips_32 16 - -16
> apply_r_mips_64 76 - -76
> apply_r_mips_highest 88 - -88
> apply_r_mips_higher 108 - -108
> apply_r_mips_26 132 - -132
> apply_r_mips_pc26 160 - -160
> apply_r_mips_pc21 160 - -160
> apply_r_mips_pc16 160 - -160
> apply_r_mips_hi16 172 - -172
> apply_r_mips_lo16 356 - -356
> Total: Before=2608, After=2048, chg -21.47%
> add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
> Data old new delta
> Total: Before=12, After=12, chg +0.00%
> add/remove: 0/1 grow/shrink: 0/0 up/down: 0/-248 (-248)
> RO Data old new delta
> reloc_handlers 248 - -248
> Total: Before=248, After=0, chg -100.00%
>
> All functions were collapsed into a single one that is called
> directly by $(srctree)/kernel/module.c.
>
> Signed-off-by: Alexander Lobakin <alobakin@...me>
Reviewed-by: Jiaxun Yang <jiaxun.yang@...goat.com>
> ---
> arch/mips/kernel/module.c | 109 ++++++++++++++++++--------------------
> 1 file changed, 52 insertions(+), 57 deletions(-)
>
> diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
> index 3c0c3d1260c1..14f46d17500a 100644
> --- a/arch/mips/kernel/module.c
> +++ b/arch/mips/kernel/module.c
> @@ -40,22 +40,13 @@ void *module_alloc(unsigned long size)
> }
> #endif
>
> -static int apply_r_mips_none(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> -{
> - return 0;
> -}
> -
> -static int apply_r_mips_32(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static void apply_r_mips_32(u32 *location, u32 base, Elf_Addr v)
> {
> *location = base + v;
> -
> - return 0;
> }
>
> -static int apply_r_mips_26(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_26(struct module *me, u32 *location, u32 base,
> + Elf_Addr v)
> {
> if (v % 4) {
> pr_err("module %s: dangerous R_MIPS_26 relocation\n",
> @@ -75,8 +66,8 @@ static int apply_r_mips_26(struct module *me, u32 *location,
> return 0;
> }
>
> -static int apply_r_mips_hi16(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_hi16(struct module *me, u32 *location, Elf_Addr v,
> + bool rela)
> {
> struct mips_hi16 *n;
>
> @@ -217,26 +208,25 @@ static int apply_r_mips_pc(struct module *me, u32 *location, u32 base,
> return 0;
> }
>
> -static int apply_r_mips_pc16(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_pc16(struct module *me, u32 *location, u32 base,
> + Elf_Addr v)
> {
> return apply_r_mips_pc(me, location, base, v, 16);
> }
>
> -static int apply_r_mips_pc21(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_pc21(struct module *me, u32 *location, u32 base,
> + Elf_Addr v)
> {
> return apply_r_mips_pc(me, location, base, v, 21);
> }
>
> -static int apply_r_mips_pc26(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_pc26(struct module *me, u32 *location, u32 base,
> + Elf_Addr v)
> {
> return apply_r_mips_pc(me, location, base, v, 26);
> }
>
> -static int apply_r_mips_64(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_64(u32 *location, Elf_Addr v, bool rela)
> {
> if (WARN_ON(!rela))
> return -EINVAL;
> @@ -246,8 +236,7 @@ static int apply_r_mips_64(struct module *me, u32 *location,
> return 0;
> }
>
> -static int apply_r_mips_higher(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_higher(u32 *location, Elf_Addr v, bool rela)
> {
> if (WARN_ON(!rela))
> return -EINVAL;
> @@ -258,8 +247,7 @@ static int apply_r_mips_higher(struct module *me, u32 *location,
> return 0;
> }
>
> -static int apply_r_mips_highest(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela)
> +static int apply_r_mips_highest(u32 *location, Elf_Addr v, bool rela)
> {
> if (WARN_ON(!rela))
> return -EINVAL;
> @@ -272,12 +260,14 @@ static int apply_r_mips_highest(struct module *me, u32 *location,
>
> /**
> * reloc_handler() - Apply a particular relocation to a module
> + * @type: type of the relocation to apply
> * @me: the module to apply the reloc to
> * @location: the address at which the reloc is to be applied
> * @base: the existing value at location for REL-style; 0 for RELA-style
> * @v: the value of the reloc, with addend for RELA-style
> + * @rela: indication of is this a RELA (true) or REL (false) relocation
> *
> - * Each implemented reloc_handler function applies a particular type of
> + * Each implemented relocation function applies a particular type of
> * relocation to the module @me. Relocs that may be found in either REL or RELA
> * variants can be handled by making use of the @base & @v parameters which are
> * set to values which abstract the difference away from the particular reloc
> @@ -285,23 +275,40 @@ static int apply_r_mips_highest(struct module *me, u32 *location,
> *
> * Return: 0 upon success, else -ERRNO
> */
> -typedef int (*reloc_handler)(struct module *me, u32 *location,
> - u32 base, Elf_Addr v, bool rela);
> -
> -/* The handlers for known reloc types */
> -static reloc_handler reloc_handlers[] = {
> - [R_MIPS_NONE] = apply_r_mips_none,
> - [R_MIPS_32] = apply_r_mips_32,
> - [R_MIPS_26] = apply_r_mips_26,
> - [R_MIPS_HI16] = apply_r_mips_hi16,
> - [R_MIPS_LO16] = apply_r_mips_lo16,
> - [R_MIPS_PC16] = apply_r_mips_pc16,
> - [R_MIPS_64] = apply_r_mips_64,
> - [R_MIPS_HIGHER] = apply_r_mips_higher,
> - [R_MIPS_HIGHEST] = apply_r_mips_highest,
> - [R_MIPS_PC21_S2] = apply_r_mips_pc21,
> - [R_MIPS_PC26_S2] = apply_r_mips_pc26,
> -};
> +static int reloc_handler(u32 type, struct module *me, u32 *location, u32 base,
> + Elf_Addr v, bool rela)
> +{
> + switch (type) {
> + case R_MIPS_NONE:
> + break;
> + case R_MIPS_32:
> + apply_r_mips_32(location, base, v);
> + break;
> + case R_MIPS_26:
> + return apply_r_mips_26(me, location, base, v);
> + case R_MIPS_HI16:
> + return apply_r_mips_hi16(me, location, v, rela);
> + case R_MIPS_LO16:
> + return apply_r_mips_lo16(me, location, base, v, rela);
> + case R_MIPS_PC16:
> + return apply_r_mips_pc16(me, location, base, v);
> + case R_MIPS_PC21_S2:
> + return apply_r_mips_pc21(me, location, base, v);
> + case R_MIPS_PC26_S2:
> + return apply_r_mips_pc26(me, location, base, v);
> + case R_MIPS_64:
> + return apply_r_mips_64(location, v, rela);
> + case R_MIPS_HIGHER:
> + return apply_r_mips_higher(location, v, rela);
> + case R_MIPS_HIGHEST:
> + return apply_r_mips_highest(location, v, rela);
> + default:
> + pr_err("%s: Unknown relocation type %u\n", me->name, type);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
>
> static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
> unsigned int symindex, unsigned int relsec,
> @@ -311,7 +318,6 @@ static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
> Elf_Mips_Rel *rel;
> Elf_Mips_Rela *rela;
> } r;
> - reloc_handler handler;
> Elf_Sym *sym;
> u32 *location, base;
> unsigned int i, type;
> @@ -343,17 +349,6 @@ static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
> }
>
> type = ELF_MIPS_R_TYPE(*r.rel);
> - if (type < ARRAY_SIZE(reloc_handlers))
> - handler = reloc_handlers[type];
> - else
> - handler = NULL;
> -
> - if (!handler) {
> - pr_err("%s: Unknown relocation type %u\n",
> - me->name, type);
> - err = -EINVAL;
> - goto out;
> - }
>
> if (rela) {
> v = sym->st_value + r.rela->r_addend;
> @@ -365,7 +360,7 @@ static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
> r.rel = &r.rel[1];
> }
>
> - err = handler(me, location, base, v, rela);
> + err = reloc_handler(type, me, location, base, v, rela);
> if (err)
> goto out;
> }
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