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-rw-r--r--arch/arm/kernel/module-plts.c87
1 files changed, 60 insertions, 27 deletions
diff --git a/arch/arm/kernel/module-plts.c b/arch/arm/kernel/module-plts.c
index 3a5cba90c971..3d0c2e4dda1d 100644
--- a/arch/arm/kernel/module-plts.c
+++ b/arch/arm/kernel/module-plts.c
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
+ * Copyright (C) 2014-2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
@@ -31,9 +31,17 @@ struct plt_entries {
u32 lit[PLT_ENT_COUNT];
};
+static bool in_init(const struct module *mod, unsigned long loc)
+{
+ return loc - (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 = (struct plt_entries *)mod->arch.plt->sh_addr;
+ struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core :
+ &mod->arch.init;
+
+ struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr;
int idx = 0;
/*
@@ -41,9 +49,9 @@ u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
* relocations are sorted, this will be the last entry we allocated.
* (if one exists).
*/
- if (mod->arch.plt_count > 0) {
- plt += (mod->arch.plt_count - 1) / PLT_ENT_COUNT;
- idx = (mod->arch.plt_count - 1) % PLT_ENT_COUNT;
+ if (pltsec->plt_count > 0) {
+ plt += (pltsec->plt_count - 1) / PLT_ENT_COUNT;
+ idx = (pltsec->plt_count - 1) % PLT_ENT_COUNT;
if (plt->lit[idx] == val)
return (u32)&plt->ldr[idx];
@@ -53,8 +61,8 @@ u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
plt++;
}
- mod->arch.plt_count++;
- BUG_ON(mod->arch.plt_count * PLT_ENT_SIZE > mod->arch.plt->sh_size);
+ pltsec->plt_count++;
+ BUG_ON(pltsec->plt_count * PLT_ENT_SIZE > pltsec->plt->sh_size);
if (!idx)
/* Populate a new set of entries */
@@ -129,7 +137,7 @@ static bool duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num)
/* Count how many PLT entries we may need */
static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base,
- const Elf32_Rel *rel, int num)
+ const Elf32_Rel *rel, int num, Elf32_Word dstidx)
{
unsigned int ret = 0;
const Elf32_Sym *s;
@@ -144,13 +152,17 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base,
case R_ARM_THM_JUMP24:
/*
* We only have to consider branch targets that resolve
- * to undefined symbols. This is not simply a heuristic,
- * it is a fundamental limitation, since the PLT itself
- * is part of the module, and needs to be within range
- * as well, so modules can never grow beyond that limit.
+ * to symbols that are defined in a different section.
+ * This is not simply a heuristic, it is a fundamental
+ * limitation, since there is no guaranteed way to emit
+ * PLT entries sufficiently close to the branch if the
+ * section size exceeds the range of a branch
+ * instruction. So ignore relocations against defined
+ * symbols if they live in the same section as the
+ * relocation target.
*/
s = syms + ELF32_R_SYM(rel[i].r_info);
- if (s->st_shndx != SHN_UNDEF)
+ if (s->st_shndx == dstidx)
break;
/*
@@ -161,7 +173,12 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base,
* So we need to support them, but there is no need to
* take them into consideration when trying to optimize
* this code. So let's only check for duplicates when
- * the addend is zero.
+ * the addend is zero. (Note that calls into the core
+ * module via init PLT entries could involve section
+ * relative symbol references with non-zero addends, for
+ * which we may end up emitting duplicates, but the init
+ * PLT is released along with the rest of the .init
+ * region as soon as module loading completes.)
*/
if (!is_zero_addend_relocation(base, rel + i) ||
!duplicate_rel(base, rel, i))
@@ -174,7 +191,8 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base,
int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
char *secstrings, struct module *mod)
{
- unsigned long plts = 0;
+ unsigned long core_plts = 0;
+ unsigned long init_plts = 0;
Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum;
Elf32_Sym *syms = NULL;
@@ -184,13 +202,15 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
*/
for (s = sechdrs; s < sechdrs_end; ++s) {
if (strcmp(".plt", secstrings + s->sh_name) == 0)
- mod->arch.plt = s;
+ mod->arch.core.plt = s;
+ else if (strcmp(".init.plt", secstrings + s->sh_name) == 0)
+ mod->arch.init.plt = s;
else if (s->sh_type == SHT_SYMTAB)
syms = (Elf32_Sym *)s->sh_addr;
}
- if (!mod->arch.plt) {
- pr_err("%s: module PLT section missing\n", mod->name);
+ if (!mod->arch.core.plt || !mod->arch.init.plt) {
+ pr_err("%s: module PLT section(s) missing\n", mod->name);
return -ENOEXEC;
}
if (!syms) {
@@ -213,16 +233,29 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
/* sort by type and symbol index */
sort(rels, numrels, sizeof(Elf32_Rel), cmp_rel, NULL);
- plts += count_plts(syms, dstsec->sh_addr, rels, numrels);
+ if (strncmp(secstrings + dstsec->sh_name, ".init", 5) != 0)
+ core_plts += count_plts(syms, dstsec->sh_addr, rels,
+ numrels, s->sh_info);
+ else
+ init_plts += count_plts(syms, dstsec->sh_addr, rels,
+ numrels, s->sh_info);
}
- 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;
-
- pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size);
+ 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.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: plt=%x, init.plt=%x\n", __func__,
+ mod->arch.core.plt->sh_size, mod->arch.init.plt->sh_size);
return 0;
}
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