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ARM: kernel: merge core and init PLTs

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The PLT code uses a separate .init.plt section to allocate PLT entries
for jump and call instructions in __init code. However, even for fairly
sizable modules like mac80211.ko, we only end up with a couple of PLT
entries in the .init section, and so we can simplify the code
significantly by emitting all PLT entries into the same section.

Tested-by: Jongsung Kim <neidhard.kim@lge.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
This commit is contained in:
Ard Biesheuvel 2016-08-16 17:21:02 +02:00
parent 3eab887a55
commit 35fa91eed8
3 changed files with 23 additions and 50 deletions
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6
arch/arm/include/asm/module.h
View File

@ -23,10 +23,8 @@ struct mod_arch_specific {
struct unwind_table *unwind[ARM_SEC_MAX];
#endif
#ifdef CONFIG_ARM_MODULE_PLTS
struct elf32_shdr *core_plt;
struct elf32_shdr *init_plt;
int core_plt_count;
int init_plt_count;
struct elf32_shdr *plt;
int plt_count;
#endif
};

64
arch/arm/kernel/module-plts.c
View File

@ -30,28 +30,16 @@ struct plt_entries {
u32 lit[PLT_ENT_COUNT];
};
static bool in_init(const struct module *mod, u32 addr)
{
return addr - (u32)mod->init_layout.base < mod->init_layout.size;
}
u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
{
struct plt_entries *plt, *plt_end;
int c, *count;
int c;
if (in_init(mod, loc)) {
plt = (void *)mod->arch.init_plt->sh_addr;
plt_end = (void *)plt + mod->arch.init_plt->sh_size;
count = &mod->arch.init_plt_count;
} else {
plt = (void *)mod->arch.core_plt->sh_addr;
plt_end = (void *)plt + mod->arch.core_plt->sh_size;
count = &mod->arch.core_plt_count;
}
plt = (void *)mod->arch.plt->sh_addr;
plt_end = (void *)plt + mod->arch.plt->sh_size;
/* Look for an existing entry pointing to 'val' */
for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) {
for (c = mod->arch.plt_count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) {
int i;
if (!c) {
@ -60,13 +48,13 @@ u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
{ [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, },
{ val, }
};
++*count;
mod->arch.plt_count++;
return (u32)plt->ldr;
}
for (i = 0; i < PLT_ENT_COUNT; i++) {
if (!plt->lit[i]) {
plt->lit[i] = val;
++*count;
mod->arch.plt_count++;
}
if (plt->lit[i] == val)
return (u32)&plt->ldr[i];
@ -132,21 +120,19 @@ static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num)
int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
char *secstrings, struct module *mod)
{
unsigned long core_plts = 0, init_plts = 0;
unsigned long plts = 0;
Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum;
/*
* To store the PLTs, we expand the .text section for core module code
* and the .init.text section for initialization code.
* and for initialization code.
*/
for (s = sechdrs; s < sechdrs_end; ++s)
if (strcmp(".core.plt", secstrings + s->sh_name) == 0)
mod->arch.core_plt = s;
else if (strcmp(".init.plt", secstrings + s->sh_name) == 0)
mod->arch.init_plt = s;
if (strcmp(".plt", secstrings + s->sh_name) == 0)
mod->arch.plt = s;
if (!mod->arch.core_plt || !mod->arch.init_plt) {
pr_err("%s: sections missing\n", mod->name);
if (!mod->arch.plt) {
pr_err("%s: module PLT section missing\n", mod->name);
return -ENOEXEC;
}
@ -158,26 +144,16 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
if (s->sh_type != SHT_REL)
continue;
if (strstr(secstrings + s->sh_name, ".init"))
init_plts += count_plts(dstsec->sh_addr, rels, numrels);
else
core_plts += count_plts(dstsec->sh_addr, rels, numrels);
plts += count_plts(dstsec->sh_addr, rels, numrels);
}
mod->arch.core_plt->sh_type = SHT_NOBITS;
mod->arch.core_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
mod->arch.core_plt->sh_addralign = L1_CACHE_BYTES;
mod->arch.core_plt->sh_size = round_up(core_plts * PLT_ENT_SIZE,
sizeof(struct plt_entries));
mod->arch.core_plt_count = 0;
mod->arch.plt->sh_type = SHT_NOBITS;
mod->arch.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
mod->arch.plt->sh_addralign = L1_CACHE_BYTES;
mod->arch.plt->sh_size = round_up(plts * PLT_ENT_SIZE,
sizeof(struct plt_entries));
mod->arch.plt_count = 0;
mod->arch.init_plt->sh_type = SHT_NOBITS;
mod->arch.init_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
mod->arch.init_plt->sh_addralign = L1_CACHE_BYTES;
mod->arch.init_plt->sh_size = round_up(init_plts * PLT_ENT_SIZE,
sizeof(struct plt_entries));
mod->arch.init_plt_count = 0;
pr_debug("%s: core.plt=%x, init.plt=%x\n", __func__,
mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size);
pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size);
return 0;
}

3
arch/arm/kernel/module.lds
View File

@ -1,4 +1,3 @@
SECTIONS {
.core.plt : { BYTE(0) }
.init.plt : { BYTE(0) }
.plt : { BYTE(0) }
}