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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170// SPDX-License-Identifier: GPL-2.0-or-later/* * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com> */
/* * This file reads all the special sections which have alternate instructions * which can be patched in or redirected to at runtime. */
#include <stdlib.h>#include <string.h>
#include <arch/special.h>#include <objtool/builtin.h>#include <objtool/special.h>#include <objtool/warn.h>
struct special_entry { const char *sec; bool group, jump_or_nop; unsigned char size, orig, new; unsigned char orig_len, new_len; /* group only */ unsigned char feature; /* ALTERNATIVE macro CPU feature */ unsigned char key; /* jump_label key */};
static const struct special_entry entries[] = { { .sec = ".altinstructions", .group = true, .size = ALT_ENTRY_SIZE, .orig = ALT_ORIG_OFFSET, .orig_len = ALT_ORIG_LEN_OFFSET, .new = ALT_NEW_OFFSET, .new_len = ALT_NEW_LEN_OFFSET, .feature = ALT_FEATURE_OFFSET, }, { .sec = "__jump_table", .jump_or_nop = true, .size = JUMP_ENTRY_SIZE, .orig = JUMP_ORIG_OFFSET, .new = JUMP_NEW_OFFSET, .key = JUMP_KEY_OFFSET, }, { .sec = "__ex_table", .size = EX_ENTRY_SIZE, .orig = EX_ORIG_OFFSET, .new = EX_NEW_OFFSET, }, {},};
void __weak arch_handle_alternative(struct special_alt *alt){}
static void reloc_to_sec_off(struct reloc *reloc, struct section **sec, unsigned long *off){ *sec = reloc->sym->sec; *off = reloc->sym->offset + reloc_addend(reloc);}
static int get_alt_entry(struct elf *elf, const struct special_entry *entry, struct section *sec, int idx, struct special_alt *alt){ struct reloc *orig_reloc, *new_reloc; unsigned long offset;
offset = idx * entry->size;
alt->group = entry->group; alt->jump_or_nop = entry->jump_or_nop;
if (alt->group) { alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset + entry->orig_len); alt->new_len = *(unsigned char *)(sec->data->d_buf + offset + entry->new_len); alt->feature = *(unsigned int *)(sec->data->d_buf + offset + entry->feature); }
orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig); if (!orig_reloc) { ERROR_FUNC(sec, offset + entry->orig, "can't find orig reloc"); return -1; }
reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off);
arch_handle_alternative(alt);
if (!entry->group || alt->new_len) { new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new); if (!new_reloc) { ERROR_FUNC(sec, offset + entry->new, "can't find new reloc"); return -1; }
reloc_to_sec_off(new_reloc, &alt->new_sec, &alt->new_off);
/* _ASM_EXTABLE_EX hack */ if (alt->new_off >= 0x7ffffff0) alt->new_off -= 0x7ffffff0; }
if (entry->key) { struct reloc *key_reloc;
key_reloc = find_reloc_by_dest(elf, sec, offset + entry->key); if (!key_reloc) { ERROR_FUNC(sec, offset + entry->key, "can't find key reloc"); return -1; } alt->key_addend = reloc_addend(key_reloc); }
return 0;}
/* * Read all the special sections and create a list of special_alt structs which * describe all the alternate instructions which can be patched in or * redirected to at runtime. */int special_get_alts(struct elf *elf, struct list_head *alts){ const struct special_entry *entry; struct section *sec; unsigned int nr_entries; struct special_alt *alt; int idx;
INIT_LIST_HEAD(alts);
for (entry = entries; entry->sec; entry++) { sec = find_section_by_name(elf, entry->sec); if (!sec) continue;
if (sec_size(sec) % entry->size != 0) { ERROR("%s size not a multiple of %d", sec->name, entry->size); return -1; }
nr_entries = sec_size(sec) / entry->size;
for (idx = 0; idx < nr_entries; idx++) { alt = malloc(sizeof(*alt)); if (!alt) { ERROR_GLIBC("malloc failed"); return -1; } memset(alt, 0, sizeof(*alt));
if (get_alt_entry(elf, entry, sec, idx, alt)) return -1;
list_add_tail(&alt->list, alts); } }
return 0;}