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

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index ec94f1359c00e6cc9da17e9e70315f28615455ec..4b3378c715182e0eabd880668eacb88f88bed4b1 100644 (file)
--- 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);