From da8f9cf7e721c690ca169fa88641a6c4cee5cae4 Mon Sep 17 00:00:00 2001 From: "Borislav Petkov (AMD)" Date: Tue, 30 Jan 2024 11:59:39 +0100 Subject: 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) Link: https://lore.kernel.org/r/20240130105941.19707-3-bp@alien8.de --- arch/x86/kernel/alternative.c | 59 ++++++++++++------------------------------- 1 file changed, 16 insertions(+), 43 deletions(-) (limited to 'arch') diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index ec94f1359c00..4b3378c71518 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -216,47 +216,12 @@ static int skip_nops(u8 *buf, int offset, int len) 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 * 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) { struct insn insn; @@ -265,7 +230,14 @@ static void __init_or_module noinline optimize_nops(const u8 * const instr, u8 * 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); } -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) { 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; - if (__optimize_nops(instr, buf, instrlen, &insn, &next, &prev, &target)) - continue; - switch (insn.opcode.bytes[0]) { case 0x0f: 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. */ DEFINE_ASM_FUNC(nop_func, "", .entry.text); EXPORT_SYMBOL_GPL(nop_func); -- cgit v1.2.3