mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-05-24 10:39:52 +00:00
x86/alternatives: Get rid of __optimize_nops()
There's no need to carve out bits of the NOP optimization functionality and look at JMP opcodes - simply do one more NOPs optimization pass at the end of patching. A lot simpler code. Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20240130105941.19707-3-bp@alien8.de
This commit is contained in:
parent
f796c75837
commit
da8f9cf7e7
1 changed files with 16 additions and 43 deletions
|
@ -216,47 +216,12 @@ static int skip_nops(u8 *buf, int offset, int len)
|
||||||
return offset;
|
return offset;
|
||||||
}
|
}
|
||||||
|
|
||||||
/*
|
|
||||||
* Optimize a sequence of NOPs, possibly preceded by an unconditional jump
|
|
||||||
* to the end of the NOP sequence into a single NOP.
|
|
||||||
*/
|
|
||||||
static bool
|
|
||||||
__optimize_nops(const u8 * const instr, u8 *buf, size_t len, struct insn *insn, int *next, int *prev, int *target)
|
|
||||||
{
|
|
||||||
int i = *next - insn->length;
|
|
||||||
|
|
||||||
switch (insn->opcode.bytes[0]) {
|
|
||||||
case JMP8_INSN_OPCODE:
|
|
||||||
case JMP32_INSN_OPCODE:
|
|
||||||
*prev = i;
|
|
||||||
*target = *next + insn->immediate.value;
|
|
||||||
return false;
|
|
||||||
}
|
|
||||||
|
|
||||||
if (insn_is_nop(insn)) {
|
|
||||||
int nop = i;
|
|
||||||
|
|
||||||
*next = skip_nops(buf, *next, len);
|
|
||||||
if (*target && *next == *target)
|
|
||||||
nop = *prev;
|
|
||||||
|
|
||||||
add_nop(buf + nop, *next - nop);
|
|
||||||
DUMP_BYTES(ALT, buf, len, "%px: [%d:%d) optimized NOPs: ", instr, nop, *next);
|
|
||||||
return true;
|
|
||||||
}
|
|
||||||
|
|
||||||
*target = 0;
|
|
||||||
return false;
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
/*
|
||||||
* "noinline" to cause control flow change and thus invalidate I$ and
|
* "noinline" to cause control flow change and thus invalidate I$ and
|
||||||
* cause refetch after modification.
|
* cause refetch after modification.
|
||||||
*/
|
*/
|
||||||
static void __init_or_module noinline optimize_nops(const u8 * const instr, u8 *buf, size_t len)
|
static void noinline optimize_nops(const u8 * const instr, u8 *buf, size_t len)
|
||||||
{
|
{
|
||||||
int prev, target = 0;
|
|
||||||
|
|
||||||
for (int next, i = 0; i < len; i = next) {
|
for (int next, i = 0; i < len; i = next) {
|
||||||
struct insn insn;
|
struct insn insn;
|
||||||
|
|
||||||
|
@ -265,7 +230,14 @@ static void __init_or_module noinline optimize_nops(const u8 * const instr, u8 *
|
||||||
|
|
||||||
next = i + insn.length;
|
next = i + insn.length;
|
||||||
|
|
||||||
__optimize_nops(instr, buf, len, &insn, &next, &prev, &target);
|
if (insn_is_nop(&insn)) {
|
||||||
|
int nop = i;
|
||||||
|
|
||||||
|
next = skip_nops(buf, next, len);
|
||||||
|
|
||||||
|
add_nop(buf + nop, next - nop);
|
||||||
|
DUMP_BYTES(ALT, buf, len, "%px: [%d:%d) optimized NOPs: ", instr, nop, next);
|
||||||
|
}
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
|
@ -339,10 +311,8 @@ bool need_reloc(unsigned long offset, u8 *src, size_t src_len)
|
||||||
return (target < src || target > src + src_len);
|
return (target < src || target > src + src_len);
|
||||||
}
|
}
|
||||||
|
|
||||||
void apply_relocation(u8 *buf, const u8 * const instr, size_t instrlen, u8 *repl, size_t repl_len)
|
static void __apply_relocation(u8 *buf, const u8 * const instr, size_t instrlen, u8 *repl, size_t repl_len)
|
||||||
{
|
{
|
||||||
int prev, target = 0;
|
|
||||||
|
|
||||||
for (int next, i = 0; i < instrlen; i = next) {
|
for (int next, i = 0; i < instrlen; i = next) {
|
||||||
struct insn insn;
|
struct insn insn;
|
||||||
|
|
||||||
|
@ -351,9 +321,6 @@ void apply_relocation(u8 *buf, const u8 * const instr, size_t instrlen, u8 *repl
|
||||||
|
|
||||||
next = i + insn.length;
|
next = i + insn.length;
|
||||||
|
|
||||||
if (__optimize_nops(instr, buf, instrlen, &insn, &next, &prev, &target))
|
|
||||||
continue;
|
|
||||||
|
|
||||||
switch (insn.opcode.bytes[0]) {
|
switch (insn.opcode.bytes[0]) {
|
||||||
case 0x0f:
|
case 0x0f:
|
||||||
if (insn.opcode.bytes[1] < 0x80 ||
|
if (insn.opcode.bytes[1] < 0x80 ||
|
||||||
|
@ -398,6 +365,12 @@ void apply_relocation(u8 *buf, const u8 * const instr, size_t instrlen, u8 *repl
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
|
void apply_relocation(u8 *buf, const u8 * const instr, size_t instrlen, u8 *repl, size_t repl_len)
|
||||||
|
{
|
||||||
|
__apply_relocation(buf, instr, instrlen, repl, repl_len);
|
||||||
|
optimize_nops(instr, buf, repl_len);
|
||||||
|
}
|
||||||
|
|
||||||
/* Low-level backend functions usable from alternative code replacements. */
|
/* Low-level backend functions usable from alternative code replacements. */
|
||||||
DEFINE_ASM_FUNC(nop_func, "", .entry.text);
|
DEFINE_ASM_FUNC(nop_func, "", .entry.text);
|
||||||
EXPORT_SYMBOL_GPL(nop_func);
|
EXPORT_SYMBOL_GPL(nop_func);
|
||||||
|
|
Loading…
Add table
Reference in a new issue