From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 534A0C433F5 for ; Tue, 8 Mar 2022 15:56:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348208AbiCHP5m (ORCPT ); Tue, 8 Mar 2022 10:57:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348052AbiCHP4F (ORCPT ); Tue, 8 Mar 2022 10:56:05 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EE2964F9C1 for ; Tue, 8 Mar 2022 07:55:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=eML9RLDC/cQALZAn3V17jKIU3Pd2WZbKiLikbOlkBgk=; b=k7dqYZIW8opId2R5YfBfyKs2ST oeegECYJWXUKSW3ABcuOmV0T9d1SGZV08N4V8KQn0IOlpJCj9DU5VPExha6cZd+Fr7/lGjpHnG1Fi kabPaMf9PwkN+yDln0jkZufHNAD/ONAAeMsc6zy+EzSuhk2EuJm4pxuk7MaiNOn2qUO0eEJdtkUg/ ahJPgWe2zTwM8vACbyLqmdS0iwbkAV56MaJA7N6BmccV0zpbJXcahBGO6gHgNVXukM6rrq8Zu/Rgr zd9YhcKGIPayeuSd+8J5FAEQbaDsEsH7/pte7LMSkkoaPFYHkvb1xlooW/p1s1koSWZPidA8DcIOp gwcAz6NA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nRcAc-00GUiX-LV; Tue, 08 Mar 2022 15:54:42 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 3F722302AD4; Tue, 8 Mar 2022 16:54:40 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 509702B561927; Tue, 8 Mar 2022 16:54:39 +0100 (CET) Message-ID: <20220308154318.464998838@infradead.org> User-Agent: quilt/0.66 Date: Tue, 08 Mar 2022 16:30:33 +0100 From: Peter Zijlstra To: x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com, jpoimboe@redhat.com, andrew.cooper3@citrix.com Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, ndesaulniers@google.com, keescook@chromium.org, samitolvanen@google.com, mark.rutland@arm.com, alyssa.milburn@intel.com, mbenes@suse.cz, rostedt@goodmis.org, mhiramat@kernel.org, alexei.starovoitov@gmail.com Subject: [PATCH v4 22/45] x86/ibt,bpf: Add ENDBR instructions to prologue and trampoline References: <20220308153011.021123062@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With IBT enabled builds we need ENDBR instructions at indirect jump target sites, since we start execution of the JIT'ed code through an indirect jump, the very first instruction needs to be ENDBR. Similarly, since eBPF tail-calls use indirect branches, their landing site needs to be an ENDBR too. The trampolines need similar adjustment. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/net/bpf_jit_comp.c | 16 ++++++++++++++-- kernel/bpf/trampoline.c | 20 ++++---------------- 2 files changed, 18 insertions(+), 18 deletions(-) --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -46,6 +46,12 @@ static u8 *emit_code(u8 *ptr, u32 bytes, #define EMIT4_off32(b1, b2, b3, b4, off) \ do { EMIT4(b1, b2, b3, b4); EMIT(off, 4); } while (0) +#ifdef CONFIG_X86_KERNEL_IBT +#define EMIT_ENDBR() EMIT(gen_endbr(), 4) +#else +#define EMIT_ENDBR() +#endif + static bool is_imm8(int value) { return value <= 127 && value >= -128; @@ -241,7 +247,7 @@ struct jit_context { /* Number of bytes emit_patch() needs to generate instructions */ #define X86_PATCH_SIZE 5 /* Number of bytes that will be skipped on tailcall */ -#define X86_TAIL_CALL_OFFSET 11 +#define X86_TAIL_CALL_OFFSET (11 + ENDBR_INSN_SIZE) static void push_callee_regs(u8 **pprog, bool *callee_regs_used) { @@ -286,6 +292,7 @@ static void emit_prologue(u8 **pprog, u3 /* BPF trampoline can be made to work without these nops, * but let's waste 5 bytes for now and optimize later */ + EMIT_ENDBR(); memcpy(prog, x86_nops[5], X86_PATCH_SIZE); prog += X86_PATCH_SIZE; if (!ebpf_from_cbpf) { @@ -296,6 +303,10 @@ static void emit_prologue(u8 **pprog, u3 } EMIT1(0x55); /* push rbp */ EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */ + + /* X86_TAIL_CALL_OFFSET is here */ + EMIT_ENDBR(); + /* sub rsp, rounded_stack_depth */ if (stack_depth) EMIT3_off32(0x48, 0x81, 0xEC, round_up(stack_depth, 8)); @@ -2028,10 +2039,11 @@ int arch_prepare_bpf_trampoline(struct b /* skip patched call instruction and point orig_call to actual * body of the kernel function. */ - orig_call += X86_PATCH_SIZE; + orig_call += X86_PATCH_SIZE + ENDBR_INSN_SIZE; prog = image; + EMIT_ENDBR(); EMIT1(0x55); /* push rbp */ EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */ EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */