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c27c753ea6
__static_call_fixup() invokes __static_call_transform() without holding
text_mutex, which causes lockdep to complain in text_poke_bp().
Adding the proper locking cures that, but as this is either used during
early boot or during module finalizing, it's not required to use
text_poke_bp(). Add an argument to __static_call_transform() which tells
it to use text_poke_early() for it.
Fixes: ee88d363d1
("x86,static_call: Use alternative RET encoding")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
157 lines
3.8 KiB
C
157 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/static_call.h>
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#include <linux/memory.h>
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#include <linux/bug.h>
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#include <asm/text-patching.h>
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enum insn_type {
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CALL = 0, /* site call */
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NOP = 1, /* site cond-call */
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JMP = 2, /* tramp / site tail-call */
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RET = 3, /* tramp / site cond-tail-call */
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};
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/*
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* ud1 %esp, %ecx - a 3 byte #UD that is unique to trampolines, chosen such
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* that there is no false-positive trampoline identification while also being a
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* speculation stop.
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*/
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static const u8 tramp_ud[] = { 0x0f, 0xb9, 0xcc };
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/*
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* cs cs cs xorl %eax, %eax - a single 5 byte instruction that clears %[er]ax
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*/
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static const u8 xor5rax[] = { 0x2e, 0x2e, 0x2e, 0x31, 0xc0 };
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static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc };
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static void __ref __static_call_transform(void *insn, enum insn_type type,
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void *func, bool modinit)
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{
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const void *emulate = NULL;
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int size = CALL_INSN_SIZE;
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const void *code;
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switch (type) {
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case CALL:
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code = text_gen_insn(CALL_INSN_OPCODE, insn, func);
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if (func == &__static_call_return0) {
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emulate = code;
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code = &xor5rax;
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}
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break;
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case NOP:
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code = x86_nops[5];
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break;
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case JMP:
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code = text_gen_insn(JMP32_INSN_OPCODE, insn, func);
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break;
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case RET:
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if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
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code = text_gen_insn(JMP32_INSN_OPCODE, insn, &__x86_return_thunk);
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else
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code = &retinsn;
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break;
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}
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if (memcmp(insn, code, size) == 0)
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return;
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if (system_state == SYSTEM_BOOTING || modinit)
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return text_poke_early(insn, code, size);
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text_poke_bp(insn, code, size, emulate);
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}
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static void __static_call_validate(void *insn, bool tail, bool tramp)
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{
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u8 opcode = *(u8 *)insn;
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if (tramp && memcmp(insn+5, tramp_ud, 3)) {
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pr_err("trampoline signature fail");
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BUG();
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}
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if (tail) {
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if (opcode == JMP32_INSN_OPCODE ||
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opcode == RET_INSN_OPCODE)
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return;
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} else {
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if (opcode == CALL_INSN_OPCODE ||
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!memcmp(insn, x86_nops[5], 5) ||
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!memcmp(insn, xor5rax, 5))
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return;
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}
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/*
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* If we ever trigger this, our text is corrupt, we'll probably not live long.
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*/
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pr_err("unexpected static_call insn opcode 0x%x at %pS\n", opcode, insn);
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BUG();
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}
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static inline enum insn_type __sc_insn(bool null, bool tail)
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{
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/*
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* Encode the following table without branches:
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*
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* tail null insn
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* -----+-------+------
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* 0 | 0 | CALL
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* 0 | 1 | NOP
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* 1 | 0 | JMP
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* 1 | 1 | RET
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*/
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return 2*tail + null;
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}
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void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
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{
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mutex_lock(&text_mutex);
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if (tramp) {
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__static_call_validate(tramp, true, true);
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__static_call_transform(tramp, __sc_insn(!func, true), func, false);
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}
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if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) {
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__static_call_validate(site, tail, false);
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__static_call_transform(site, __sc_insn(!func, tail), func, false);
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}
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mutex_unlock(&text_mutex);
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}
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EXPORT_SYMBOL_GPL(arch_static_call_transform);
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#ifdef CONFIG_RETHUNK
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/*
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* This is called by apply_returns() to fix up static call trampolines,
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* specifically ARCH_DEFINE_STATIC_CALL_NULL_TRAMP which is recorded as
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* having a return trampoline.
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*
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* The problem is that static_call() is available before determining
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* X86_FEATURE_RETHUNK and, by implication, running alternatives.
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*
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* This means that __static_call_transform() above can have overwritten the
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* return trampoline and we now need to fix things up to be consistent.
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*/
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bool __static_call_fixup(void *tramp, u8 op, void *dest)
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{
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if (memcmp(tramp+5, tramp_ud, 3)) {
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/* Not a trampoline site, not our problem. */
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return false;
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}
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mutex_lock(&text_mutex);
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if (op == RET_INSN_OPCODE || dest == &__x86_return_thunk)
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__static_call_transform(tramp, RET, NULL, true);
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mutex_unlock(&text_mutex);
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return true;
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}
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#endif
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