GitHub-Mirror/linux-bl808
2
0
Fork 0
mirror of https://github.com/Fishwaldo/linux-bl808.git synced 2025-06-17 20:25:19 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

objtool,x86: Replace alternatives with .retpoline_sites

Browse source 
Instead of writing complete alternatives, simply provide a list of all
the retpoline thunk calls. Then the kernel is free to do with them as
it pleases. Simpler code all-round.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120309.850007165@infradead.org
This commit is contained in:
Peter Zijlstra 2021-10-26 14:01:36 +02:00
parent c509331b41
commit 134ab5bd18
6 changed files with 107 additions and 252 deletions
Download patch file Download diff file Expand all files Collapse all files

120
tools/objtool/arch/x86/decode.c
View file

@ -711,126 +711,6 @@ const char *arch_ret_insn(int len)
return ret[len-1];
}
/* asm/alternative.h ? */
#define ALTINSTR_FLAG_INV (1 << 15)
#define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV)
struct alt_instr {
s32 instr_offset; /* original instruction */
s32 repl_offset; /* offset to replacement instruction */
u16 cpuid; /* cpuid bit set for replacement */
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction */
} __packed;
static int elf_add_alternative(struct elf *elf,
struct instruction *orig, struct symbol *sym,
int cpuid, u8 orig_len, u8 repl_len)
{
const int size = sizeof(struct alt_instr);
struct alt_instr *alt;
struct section *sec;
Elf_Scn *s;
sec = find_section_by_name(elf, ".altinstructions");
if (!sec) {
sec = elf_create_section(elf, ".altinstructions",
SHF_ALLOC, 0, 0);
if (!sec) {
WARN_ELF("elf_create_section");
return -1;
}
}
s = elf_getscn(elf->elf, sec->idx);
if (!s) {
WARN_ELF("elf_getscn");
return -1;
}
sec->data = elf_newdata(s);
if (!sec->data) {
WARN_ELF("elf_newdata");
return -1;
}
sec->data->d_size = size;
sec->data->d_align = 1;
alt = sec->data->d_buf = malloc(size);
if (!sec->data->d_buf) {
perror("malloc");
return -1;
}
memset(sec->data->d_buf, 0, size);
if (elf_add_reloc_to_insn(elf, sec, sec->sh.sh_size,
R_X86_64_PC32, orig->sec, orig->offset)) {
WARN("elf_create_reloc: alt_instr::instr_offset");
return -1;
}
if (elf_add_reloc(elf, sec, sec->sh.sh_size + 4,
R_X86_64_PC32, sym, 0)) {
WARN("elf_create_reloc: alt_instr::repl_offset");
return -1;
}
alt->cpuid = bswap_if_needed(cpuid);
alt->instrlen = orig_len;
alt->replacementlen = repl_len;
sec->sh.sh_size += size;
sec->changed = true;
return 0;
}
#define X86_FEATURE_RETPOLINE ( 7*32+12)
int arch_rewrite_retpolines(struct objtool_file *file)
{
struct instruction *insn;
struct reloc *reloc;
struct symbol *sym;
char name[32] = "";
list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
if (insn->type != INSN_JUMP_DYNAMIC &&
insn->type != INSN_CALL_DYNAMIC)
continue;
if (!strcmp(insn->sec->name, ".text.__x86.indirect_thunk"))
continue;
reloc = insn->reloc;
sprintf(name, "__x86_indirect_alt_%s_%s",
insn->type == INSN_JUMP_DYNAMIC ? "jmp" : "call",
reloc->sym->name + 21);
sym = find_symbol_by_name(file->elf, name);
if (!sym) {
sym = elf_create_undef_symbol(file->elf, name);
if (!sym) {
WARN("elf_create_undef_symbol");
return -1;
}
}
if (elf_add_alternative(file->elf, insn, sym,
ALT_NOT(X86_FEATURE_RETPOLINE), 5, 5)) {
WARN("elf_add_alternative");
return -1;
}
}
return 0;
}
int arch_decode_hint_reg(u8 sp_reg, int *base)
{
switch (sp_reg) {