b24fdd0f1c
commit f43b9876e857c739d407bc56df288b0ebe1a9164 upstream. Do fine-grained Kconfig for all the various retbleed parts. NOTE: if your compiler doesn't support return thunks this will silently 'upgrade' your mitigation to IBPB, you might not like this. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> [cascardo: there is no CONFIG_OBJTOOL] [cascardo: objtool calling and option parsing has changed] Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com> [bwh: Backported to 5.10: - In scripts/Makefile.build, add the objtool option with an ifdef block, same as for other options - Adjust filename, context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
136 lines
3.3 KiB
C
136 lines
3.3 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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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, void *func)
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{
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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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break;
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case NOP:
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code = ideal_nops[NOP_ATOMIC5];
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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 (unlikely(system_state == SYSTEM_BOOTING))
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return text_poke_early(insn, code, size);
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text_poke_bp(insn, code, size, NULL);
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}
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static void __static_call_validate(void *insn, bool tail)
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{
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u8 opcode = *(u8 *)insn;
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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, ideal_nops[NOP_ATOMIC5], 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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WARN_ONCE(1, "unexpected static_call insn opcode 0x%x at %pS\n", opcode, insn);
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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);
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__static_call_transform(tramp, __sc_insn(!func, true), func);
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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);
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__static_call_transform(site, __sc_insn(!func, tail), func);
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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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if (op == RET_INSN_OPCODE || dest == &__x86_return_thunk)
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__static_call_transform(tramp, RET, NULL);
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return true;
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}
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#endif
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