Merge branch 'devel-stable' into for-linus
This commit is contained in:
Russell King
commit
81a6300186
@ -23,10 +23,8 @@ struct mod_arch_specific {
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struct unwind_table *unwind[ARM_SEC_MAX];
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#endif
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#ifdef CONFIG_ARM_MODULE_PLTS
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struct elf32_shdr *core_plt;
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struct elf32_shdr *init_plt;
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int core_plt_count;
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int init_plt_count;
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struct elf32_shdr *plt;
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int plt_count;
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#endif
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};
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@ -9,6 +9,7 @@
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#include <linux/elf.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/sort.h>
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#include <asm/cache.h>
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#include <asm/opcodes.h>
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@ -30,101 +31,142 @@ struct plt_entries {
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u32 lit[PLT_ENT_COUNT];
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};
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static bool in_init(const struct module *mod, u32 addr)
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{
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return addr - (u32)mod->init_layout.base < mod->init_layout.size;
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}
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u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
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{
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struct plt_entries *plt, *plt_end;
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int c, *count;
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struct plt_entries *plt = (struct plt_entries *)mod->arch.plt->sh_addr;
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int idx = 0;
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if (in_init(mod, loc)) {
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plt = (void *)mod->arch.init_plt->sh_addr;
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plt_end = (void *)plt + mod->arch.init_plt->sh_size;
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count = &mod->arch.init_plt_count;
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} else {
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plt = (void *)mod->arch.core_plt->sh_addr;
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plt_end = (void *)plt + mod->arch.core_plt->sh_size;
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count = &mod->arch.core_plt_count;
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/*
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* Look for an existing entry pointing to 'val'. Given that the
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* relocations are sorted, this will be the last entry we allocated.
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* (if one exists).
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*/
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if (mod->arch.plt_count > 0) {
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plt += (mod->arch.plt_count - 1) / PLT_ENT_COUNT;
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idx = (mod->arch.plt_count - 1) % PLT_ENT_COUNT;
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if (plt->lit[idx] == val)
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return (u32)&plt->ldr[idx];
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idx = (idx + 1) % PLT_ENT_COUNT;
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if (!idx)
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plt++;
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}
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/* Look for an existing entry pointing to 'val' */
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for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) {
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int i;
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mod->arch.plt_count++;
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BUG_ON(mod->arch.plt_count * PLT_ENT_SIZE > mod->arch.plt->sh_size);
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if (!c) {
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if (!idx)
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/* Populate a new set of entries */
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*plt = (struct plt_entries){
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{ [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, },
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{ val, }
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};
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++*count;
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return (u32)plt->ldr;
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else
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plt->lit[idx] = val;
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return (u32)&plt->ldr[idx];
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}
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for (i = 0; i < PLT_ENT_COUNT; i++) {
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if (!plt->lit[i]) {
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plt->lit[i] = val;
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++*count;
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}
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if (plt->lit[i] == val)
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return (u32)&plt->ldr[i];
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#define cmp_3way(a,b) ((a) < (b) ? -1 : (a) > (b))
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static int cmp_rel(const void *a, const void *b)
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{
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const Elf32_Rel *x = a, *y = b;
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int i;
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/* sort by type and symbol index */
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i = cmp_3way(ELF32_R_TYPE(x->r_info), ELF32_R_TYPE(y->r_info));
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if (i == 0)
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i = cmp_3way(ELF32_R_SYM(x->r_info), ELF32_R_SYM(y->r_info));
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return i;
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}
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static bool is_zero_addend_relocation(Elf32_Addr base, const Elf32_Rel *rel)
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{
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u32 *tval = (u32 *)(base + rel->r_offset);
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/*
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* Do a bitwise compare on the raw addend rather than fully decoding
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* the offset and doing an arithmetic comparison.
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* Note that a zero-addend jump/call relocation is encoded taking the
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* PC bias into account, i.e., -8 for ARM and -4 for Thumb2.
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*/
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switch (ELF32_R_TYPE(rel->r_info)) {
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u16 upper, lower;
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case R_ARM_THM_CALL:
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case R_ARM_THM_JUMP24:
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upper = __mem_to_opcode_thumb16(((u16 *)tval)[0]);
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lower = __mem_to_opcode_thumb16(((u16 *)tval)[1]);
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return (upper & 0x7ff) == 0x7ff && (lower & 0x2fff) == 0x2ffe;
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case R_ARM_CALL:
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case R_ARM_PC24:
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case R_ARM_JUMP24:
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return (__mem_to_opcode_arm(*tval) & 0xffffff) == 0xfffffe;
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}
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BUG();
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}
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static int duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num,
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u32 mask)
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static bool duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num)
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{
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u32 *loc1, *loc2;
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int i;
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for (i = 0; i < num; i++) {
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if (rel[i].r_info != rel[num].r_info)
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continue;
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const Elf32_Rel *prev;
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/*
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* Identical relocation types against identical symbols can
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* still result in different PLT entries if the addend in the
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* place is different. So resolve the target of the relocation
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* to compare the values.
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* Entries are sorted by type and symbol index. That means that,
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* if a duplicate entry exists, it must be in the preceding
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* slot.
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*/
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loc1 = (u32 *)(base + rel[i].r_offset);
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loc2 = (u32 *)(base + rel[num].r_offset);
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if (((*loc1 ^ *loc2) & mask) == 0)
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return 1;
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}
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return 0;
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if (!num)
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return false;
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prev = rel + num - 1;
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return cmp_rel(rel + num, prev) == 0 &&
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is_zero_addend_relocation(base, prev);
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}
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/* Count how many PLT entries we may need */
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static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num)
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static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base,
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const Elf32_Rel *rel, int num)
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{
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unsigned int ret = 0;
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const Elf32_Sym *s;
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int i;
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/*
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* Sure, this is order(n^2), but it's usually short, and not
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* time critical
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*/
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for (i = 0; i < num; i++)
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for (i = 0; i < num; i++) {
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switch (ELF32_R_TYPE(rel[i].r_info)) {
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case R_ARM_CALL:
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case R_ARM_PC24:
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case R_ARM_JUMP24:
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if (!duplicate_rel(base, rel, i,
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__opcode_to_mem_arm(0x00ffffff)))
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ret++;
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break;
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#ifdef CONFIG_THUMB2_KERNEL
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case R_ARM_THM_CALL:
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case R_ARM_THM_JUMP24:
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if (!duplicate_rel(base, rel, i,
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__opcode_to_mem_thumb32(0x07ff2fff)))
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/*
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* We only have to consider branch targets that resolve
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* to undefined symbols. This is not simply a heuristic,
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* it is a fundamental limitation, since the PLT itself
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* is part of the module, and needs to be within range
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* as well, so modules can never grow beyond that limit.
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*/
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s = syms + ELF32_R_SYM(rel[i].r_info);
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if (s->st_shndx != SHN_UNDEF)
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break;
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/*
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* Jump relocations with non-zero addends against
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* undefined symbols are supported by the ELF spec, but
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* do not occur in practice (e.g., 'jump n bytes past
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* the entry point of undefined function symbol f').
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* So we need to support them, but there is no need to
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* take them into consideration when trying to optimize
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* this code. So let's only check for duplicates when
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* the addend is zero.
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*/
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if (!is_zero_addend_relocation(base, rel + i) ||
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!duplicate_rel(base, rel, i))
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ret++;
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#endif
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}
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}
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return ret;
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}
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@ -132,52 +174,55 @@ static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num)
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int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
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char *secstrings, struct module *mod)
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{
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unsigned long core_plts = 0, init_plts = 0;
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unsigned long plts = 0;
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Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum;
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Elf32_Sym *syms = NULL;
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/*
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* To store the PLTs, we expand the .text section for core module code
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* and the .init.text section for initialization code.
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* and for initialization code.
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*/
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for (s = sechdrs; s < sechdrs_end; ++s)
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if (strcmp(".core.plt", secstrings + s->sh_name) == 0)
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mod->arch.core_plt = s;
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else if (strcmp(".init.plt", secstrings + s->sh_name) == 0)
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mod->arch.init_plt = s;
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for (s = sechdrs; s < sechdrs_end; ++s) {
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if (strcmp(".plt", secstrings + s->sh_name) == 0)
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mod->arch.plt = s;
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else if (s->sh_type == SHT_SYMTAB)
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syms = (Elf32_Sym *)s->sh_addr;
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}
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if (!mod->arch.core_plt || !mod->arch.init_plt) {
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pr_err("%s: sections missing\n", mod->name);
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if (!mod->arch.plt) {
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pr_err("%s: module PLT section missing\n", mod->name);
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return -ENOEXEC;
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}
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if (!syms) {
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pr_err("%s: module symtab section missing\n", mod->name);
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return -ENOEXEC;
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}
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for (s = sechdrs + 1; s < sechdrs_end; ++s) {
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const Elf32_Rel *rels = (void *)ehdr + s->sh_offset;
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Elf32_Rel *rels = (void *)ehdr + s->sh_offset;
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int numrels = s->sh_size / sizeof(Elf32_Rel);
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Elf32_Shdr *dstsec = sechdrs + s->sh_info;
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if (s->sh_type != SHT_REL)
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continue;
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if (strstr(secstrings + s->sh_name, ".init"))
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init_plts += count_plts(dstsec->sh_addr, rels, numrels);
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else
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core_plts += count_plts(dstsec->sh_addr, rels, numrels);
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/* ignore relocations that operate on non-exec sections */
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if (!(dstsec->sh_flags & SHF_EXECINSTR))
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continue;
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/* sort by type and symbol index */
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sort(rels, numrels, sizeof(Elf32_Rel), cmp_rel, NULL);
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plts += count_plts(syms, dstsec->sh_addr, rels, numrels);
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}
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mod->arch.core_plt->sh_type = SHT_NOBITS;
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mod->arch.core_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
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mod->arch.core_plt->sh_addralign = L1_CACHE_BYTES;
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mod->arch.core_plt->sh_size = round_up(core_plts * PLT_ENT_SIZE,
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mod->arch.plt->sh_type = SHT_NOBITS;
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mod->arch.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
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mod->arch.plt->sh_addralign = L1_CACHE_BYTES;
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mod->arch.plt->sh_size = round_up(plts * PLT_ENT_SIZE,
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sizeof(struct plt_entries));
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mod->arch.core_plt_count = 0;
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mod->arch.plt_count = 0;
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mod->arch.init_plt->sh_type = SHT_NOBITS;
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mod->arch.init_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
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mod->arch.init_plt->sh_addralign = L1_CACHE_BYTES;
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mod->arch.init_plt->sh_size = round_up(init_plts * PLT_ENT_SIZE,
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sizeof(struct plt_entries));
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mod->arch.init_plt_count = 0;
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pr_debug("%s: core.plt=%x, init.plt=%x\n", __func__,
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mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size);
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pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size);
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return 0;
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}
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@ -1,4 +1,3 @@
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SECTIONS {
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.core.plt : { BYTE(0) }
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.init.plt : { BYTE(0) }
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.plt : { BYTE(0) }
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}
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