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synced 2024-08-26 19:00:25 +00:00
![Vasily Gorbik](/assets/img/avatar_default.png)
Currently objtool headers are being included either by their base name or included via ../ from a parent directory. In case of a base name usage: #include "warn.h" #include "arch_elf.h" it does not make it apparent from which directory the file comes from. To make it slightly better, and actually to avoid name clashes some arch specific files have "arch_" suffix. And files from an arch folder have to revert to including via ../ e.g: #include "../../elf.h" With additional architectures support and the code base growth there is a need for clearer headers naming scheme for multiple reasons: 1. to make it instantly obvious where these files come from (objtool itself / objtool arch|generic folders / some other external files), 2. to avoid name clashes of objtool arch specific headers, potential obtool arch generic headers and the system header files (there is /usr/include/elf.h already), 3. to avoid ../ includes and improve code readability. 4. to give a warm fuzzy feeling to developers who are mostly kernel developers and are accustomed to linux kernel headers arranging scheme. Doesn't this make it instantly obvious where are these files come from? #include <objtool/warn.h> #include <arch/elf.h> And doesn't it look nicer to avoid ugly ../ includes? Which also guarantees this is elf.h from the objtool and not /usr/include/elf.h. #include <objtool/elf.h> This patch defines and implements new objtool headers arranging scheme. Which is: - all generic headers go to include/objtool (similar to include/linux) - all arch headers go to arch/$(SRCARCH)/include/arch (to get arch prefix). This is similar to linux arch specific "asm/*" headers but we are not abusing "asm" name and calling it what it is. This also helps to prevent name clashes (arch is not used in system headers or kernel exports). To bring objtool to this state the following things are done: 1. current top level tools/objtool/ headers are moved into include/objtool/ subdirectory, 2. arch specific headers, currently only arch/x86/include/ are moved into arch/x86/include/arch/ and were stripped of "arch_" suffix, 3. new -I$(srctree)/tools/objtool/include include path to make includes like <objtool/warn.h> possible, 4. rewriting file includes, 5. make git not to ignore include/objtool/ subdirectory. Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
165 lines
3.7 KiB
C
165 lines
3.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
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*/
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/*
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* This file reads all the special sections which have alternate instructions
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* which can be patched in or redirected to at runtime.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <arch/special.h>
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#include <objtool/builtin.h>
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#include <objtool/special.h>
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#include <objtool/warn.h>
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#include <objtool/endianness.h>
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struct special_entry {
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const char *sec;
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bool group, jump_or_nop;
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unsigned char size, orig, new;
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unsigned char orig_len, new_len; /* group only */
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unsigned char feature; /* ALTERNATIVE macro CPU feature */
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};
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struct special_entry entries[] = {
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{
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.sec = ".altinstructions",
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.group = true,
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.size = ALT_ENTRY_SIZE,
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.orig = ALT_ORIG_OFFSET,
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.orig_len = ALT_ORIG_LEN_OFFSET,
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.new = ALT_NEW_OFFSET,
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.new_len = ALT_NEW_LEN_OFFSET,
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.feature = ALT_FEATURE_OFFSET,
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},
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{
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.sec = "__jump_table",
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.jump_or_nop = true,
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.size = JUMP_ENTRY_SIZE,
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.orig = JUMP_ORIG_OFFSET,
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.new = JUMP_NEW_OFFSET,
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},
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{
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.sec = "__ex_table",
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.size = EX_ENTRY_SIZE,
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.orig = EX_ORIG_OFFSET,
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.new = EX_NEW_OFFSET,
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},
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{},
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};
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void __weak arch_handle_alternative(unsigned short feature, struct special_alt *alt)
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{
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}
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static int get_alt_entry(struct elf *elf, struct special_entry *entry,
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struct section *sec, int idx,
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struct special_alt *alt)
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{
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struct reloc *orig_reloc, *new_reloc;
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unsigned long offset;
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offset = idx * entry->size;
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alt->group = entry->group;
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alt->jump_or_nop = entry->jump_or_nop;
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if (alt->group) {
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alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset +
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entry->orig_len);
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alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +
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entry->new_len);
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}
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if (entry->feature) {
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unsigned short feature;
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feature = bswap_if_needed(*(unsigned short *)(sec->data->d_buf +
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offset +
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entry->feature));
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arch_handle_alternative(feature, alt);
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}
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orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
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if (!orig_reloc) {
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WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
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return -1;
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}
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if (orig_reloc->sym->type != STT_SECTION) {
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WARN_FUNC("don't know how to handle non-section reloc symbol %s",
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sec, offset + entry->orig, orig_reloc->sym->name);
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return -1;
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}
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alt->orig_sec = orig_reloc->sym->sec;
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alt->orig_off = orig_reloc->addend;
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if (!entry->group || alt->new_len) {
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new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);
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if (!new_reloc) {
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WARN_FUNC("can't find new reloc",
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sec, offset + entry->new);
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return -1;
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}
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alt->new_sec = new_reloc->sym->sec;
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alt->new_off = (unsigned int)new_reloc->addend;
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/* _ASM_EXTABLE_EX hack */
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if (alt->new_off >= 0x7ffffff0)
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alt->new_off -= 0x7ffffff0;
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}
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return 0;
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}
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/*
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* Read all the special sections and create a list of special_alt structs which
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* describe all the alternate instructions which can be patched in or
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* redirected to at runtime.
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*/
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int special_get_alts(struct elf *elf, struct list_head *alts)
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{
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struct special_entry *entry;
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struct section *sec;
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unsigned int nr_entries;
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struct special_alt *alt;
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int idx, ret;
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INIT_LIST_HEAD(alts);
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for (entry = entries; entry->sec; entry++) {
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sec = find_section_by_name(elf, entry->sec);
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if (!sec)
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continue;
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if (sec->len % entry->size != 0) {
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WARN("%s size not a multiple of %d",
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sec->name, entry->size);
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return -1;
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}
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nr_entries = sec->len / entry->size;
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for (idx = 0; idx < nr_entries; idx++) {
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alt = malloc(sizeof(*alt));
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if (!alt) {
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WARN("malloc failed");
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return -1;
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}
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memset(alt, 0, sizeof(*alt));
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ret = get_alt_entry(elf, entry, sec, idx, alt);
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if (ret)
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return ret;
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list_add_tail(&alt->list, alts);
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}
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}
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return 0;
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}
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