From patchwork Sat Apr 18 23:26:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luke Nelson X-Patchwork-Id: 11497055 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0D6446CA for ; Sat, 18 Apr 2020 23:27:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD90A21927 for ; Sat, 18 Apr 2020 23:27:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=cs.washington.edu header.i=@cs.washington.edu header.b="E94FC9Je" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725877AbgDRX1C (ORCPT ); Sat, 18 Apr 2020 19:27:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725804AbgDRX1C (ORCPT ); Sat, 18 Apr 2020 19:27:02 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 08B0EC061A0C for ; Sat, 18 Apr 2020 16:27:01 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id a7so2581486pju.2 for ; Sat, 18 Apr 2020 16:27:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cs.washington.edu; s=goo201206; h=from:to:cc:subject:date:message-id; bh=V1iSNi3FjSbFymrjsWR16L5sHfocV0iKd0ObfqLdCDE=; b=E94FC9JeOPlEtesZY7pnic5oqXC1UEm6VlEGtC1YgAScMnSkB2LJY+O5H4diMpuWHL d/no2M6eNI/dQY9j/v6SSyhcGs+aK1ScSuDvksCyuVmfHcNTBZoPi8j55p0j3j3YBUoZ Dp5qeYnqs74jXMUqZHwc0BsGZWmWM+mqnvNTg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=V1iSNi3FjSbFymrjsWR16L5sHfocV0iKd0ObfqLdCDE=; b=MWEGEAf5Drbx9Ck7lnVDJWouTBPl3Is6yUmmDcpJSIEGH8FYWYZsAnF1ey9wn96/i5 AwNeqz5BhXvDW2XYtm5klLcvjbyQt/kS68g7pJj/TPSvskqjaOFAZ947jR9tKttBzpLz PzXs426Ln6c15sfvl+Bx2bvCTy7of5ez1nQ0uJfOZoMbPlxnozfiCwHZTzPuIj8Bd+Bs nISn2qTXxNdE9vsZP5wFRFMRswcV92LLI9XtZpQV/LP3Ohlm31wDqG1A1CBB79XJTHVJ Jr/Sj6gpiHgQ2n2+ZTt0rCSTgTfJW23rkjtCYsJoxhjXBVcaC+fWbVPrZJlFTI4kR24u dHsw== X-Gm-Message-State: AGi0PuYW+7uXUzY7iE7tfBAiHf+O3e/SjVfWxFwroFoozWBUqHaCAwFC Q55lIgvAoECTCEKU1Dwrp93dYw== X-Google-Smtp-Source: APiQypJUg540AgQ0gfERSdqKG3/UO/88BFVywKnBq0ADggzskh4vKGlmvKwDR8ejYqwi3brMfHgq9Q== X-Received: by 2002:a17:902:a511:: with SMTP id s17mr10176108plq.33.1587252420747; Sat, 18 Apr 2020 16:27:00 -0700 (PDT) Received: from localhost.localdomain (c-73-53-94-119.hsd1.wa.comcast.net. [73.53.94.119]) by smtp.gmail.com with ESMTPSA id u7sm21429323pfu.90.2020.04.18.16.26.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Apr 2020 16:27:00 -0700 (PDT) From: Luke Nelson X-Google-Original-From: Luke Nelson To: bpf@vger.kernel.org Cc: Luke Nelson , Xi Wang , "David S. Miller" , Alexey Kuznetsov , Hideaki YOSHIFUJI , Alexei Starovoitov , Daniel Borkmann , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , John Fastabend , KP Singh , Shuah Khan , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf 1/2] bpf, x86: Fix encoding for lower 8-bit registers in BPF_STX BPF_B Date: Sat, 18 Apr 2020 16:26:53 -0700 Message-Id: <20200418232655.23870-1-luke.r.nels@gmail.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org This patch fixes an encoding bug in emit_stx for BPF_B when the source register is BPF_REG_FP. The current implementation for BPF_STX BPF_B in emit_stx saves one REX byte when the operands can be encoded using Mod-R/M alone. The lower 8 bits of registers %rax, %rbx, %rcx, and %rdx can be accessed without using a REX prefix via %al, %bl, %cl, and %dl, respectively. Other registers, (e.g., %rsi, %rdi, %rbp, %rsp) require a REX prefix to use their 8-bit equivalents (%sil, %dil, %bpl, %spl). The current code checks if the source for BPF_STX BPF_B is BPF_REG_1 or BPF_REG_2 (which map to %rdi and %rsi), in which case it emits the required REX prefix. However, it misses the case when the source is BPF_REG_FP (mapped to %rbp). The result is that BPF_STX BPF_B with BPF_REG_FP as the source operand will read from register %ch instead of the correct %bpl. This patch fixes the problem by fixing and refactoring the check on which registers need the extra REX byte. Since no BPF registers map to %rsp, there is no need to handle %spl. Fixes: 622582786c9e0 ("net: filter: x86: internal BPF JIT") Signed-off-by: Xi Wang Signed-off-by: Luke Nelson --- arch/x86/net/bpf_jit_comp.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 5ea7c2cf7ab4..42b6709e6dc7 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -158,6 +158,19 @@ static bool is_ereg(u32 reg) BIT(BPF_REG_AX)); } +/* + * is_ereg_8l() == true if BPF register 'reg' is mapped to access x86-64 + * lower 8-bit registers dil,sil,bpl,spl,r8b..r15b, which need extra byte + * of encoding. al,cl,dl,bl have simpler encoding. + */ +static bool is_ereg_8l(u32 reg) +{ + return is_ereg(reg) || + (1 << reg) & (BIT(BPF_REG_1) | + BIT(BPF_REG_2) | + BIT(BPF_REG_FP)); +} + static bool is_axreg(u32 reg) { return reg == BPF_REG_0; @@ -598,9 +611,8 @@ static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off) switch (size) { case BPF_B: /* Emit 'mov byte ptr [rax + off], al' */ - if (is_ereg(dst_reg) || is_ereg(src_reg) || - /* We have to add extra byte for x86 SIL, DIL regs */ - src_reg == BPF_REG_1 || src_reg == BPF_REG_2) + if (is_ereg(dst_reg) || is_ereg_8l(src_reg)) + /* Add extra byte for eregs or SIL,DIL,BPL in src_reg */ EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x88); else EMIT1(0x88); From patchwork Sat Apr 18 23:26:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luke Nelson X-Patchwork-Id: 11497057 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5616A112C for ; Sat, 18 Apr 2020 23:27:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DC0A21927 for ; Sat, 18 Apr 2020 23:27:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=cs.washington.edu header.i=@cs.washington.edu header.b="SHBqs5Tv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726012AbgDRX1F (ORCPT ); Sat, 18 Apr 2020 19:27:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725824AbgDRX1E (ORCPT ); Sat, 18 Apr 2020 19:27:04 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4199EC061A0C for ; Sat, 18 Apr 2020 16:27:04 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id hi11so2197645pjb.3 for ; Sat, 18 Apr 2020 16:27:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cs.washington.edu; s=goo201206; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=cUB7vdca0MZaJN7908SrqMzaWtQshCgrQGTimt6WXAg=; b=SHBqs5TvQq09m2V0itEAb9laKJVkdszNqUOMrH3jL2JPNyTiR2palwCZTYkoAhmx7D 21HzuuAMqYhvz44uZleZWuYu+EpMZDZSRCl5UJnqfDLrESBxndlSJJNaCDXcHwLhXYTD i0HCoVM1GorPe52KBFFHPYNewpeJR9fRfWzy8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=cUB7vdca0MZaJN7908SrqMzaWtQshCgrQGTimt6WXAg=; b=czvatjYWJZY1lMRu2b2OINe4+7zgr/5S8+WTD1XhRog46oi5v4/ozJoXOzQq/s7M0P Gq5tuBdl20p7mZuVzADg5n/S5AzZRsGfyhKs4tLd3AMlzx5zgklJfl+bQIe5pRngZa1f 9f31ATjq5RXvpKLycUcgqmPXoG1gRpbpyOS45nMaTEh7b3nDvIxUsW/UncBjBaic6lPR ue9ArsnaO1bRO1xKVZEk9KkFn06hgg6UpU1LvrseqMCMw/BxVfyYx/Ex1hz4ifgmomuL sf1IPxuwoe4ydfqPpzonYL41rvsJnR5mYBztNIPEI1Tj014IlrbcvSv6MgDGMTlhFCTV 3rvg== X-Gm-Message-State: AGi0Pubk2MZnjAJWVhXokafRYCkInrWVrr2VTKNFmh0CKo8qULjE4n7J Px60shErNISo9n0k6FbBuOY/EQ== X-Google-Smtp-Source: APiQypJCCGQF4cugES6slU2mpdEx2GHrEHuPITzBVyuTaVJ/RHTBYfuNwArajpvWKLf808CbnsWMow== X-Received: by 2002:a17:90a:fc89:: with SMTP id ci9mr5854418pjb.140.1587252423701; Sat, 18 Apr 2020 16:27:03 -0700 (PDT) Received: from localhost.localdomain (c-73-53-94-119.hsd1.wa.comcast.net. [73.53.94.119]) by smtp.gmail.com with ESMTPSA id u7sm21429323pfu.90.2020.04.18.16.27.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Apr 2020 16:27:03 -0700 (PDT) From: Luke Nelson X-Google-Original-From: Luke Nelson To: bpf@vger.kernel.org Cc: Luke Nelson , Xi Wang , "David S. Miller" , Alexey Kuznetsov , Hideaki YOSHIFUJI , Alexei Starovoitov , Daniel Borkmann , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , John Fastabend , KP Singh , Shuah Khan , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf 2/2] bpf, selftests: Add test for BPF_STX BPF_B storing R10 Date: Sat, 18 Apr 2020 16:26:54 -0700 Message-Id: <20200418232655.23870-2-luke.r.nels@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200418232655.23870-1-luke.r.nels@gmail.com> References: <20200418232655.23870-1-luke.r.nels@gmail.com> Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org This patch adds a test to test_verifier that writes the lower 8 bits of R10 (aka FP) using BPF_B to an array map and reads the result back. The expected behavior is that the result should be the same as first copying R10 to R9, and then storing / loading the lower 8 bits of R9. This test catches a bug that was present in the x86-64 JIT that caused an incorrect encoding for BPF_STX BPF_B when the source operand is R10. Signed-off-by: Xi Wang Signed-off-by: Luke Nelson --- .../selftests/bpf/verifier/stack_ptr.c | 40 +++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/tools/testing/selftests/bpf/verifier/stack_ptr.c b/tools/testing/selftests/bpf/verifier/stack_ptr.c index 7276620ef242..8bfeb77c60bd 100644 --- a/tools/testing/selftests/bpf/verifier/stack_ptr.c +++ b/tools/testing/selftests/bpf/verifier/stack_ptr.c @@ -315,3 +315,43 @@ }, .result = ACCEPT, }, +{ + "store PTR_TO_STACK in R10 to array map using BPF_B", + .insns = { + /* Load pointer to map. */ + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2), + BPF_MOV64_IMM(BPF_REG_0, 2), + BPF_EXIT_INSN(), + BPF_MOV64_REG(BPF_REG_1, BPF_REG_0), + /* Copy R10 to R9. */ + BPF_MOV64_REG(BPF_REG_9, BPF_REG_10), + /* Pollute other registers with unaligned values. */ + BPF_MOV64_IMM(BPF_REG_2, -1), + BPF_MOV64_IMM(BPF_REG_3, -1), + BPF_MOV64_IMM(BPF_REG_4, -1), + BPF_MOV64_IMM(BPF_REG_5, -1), + BPF_MOV64_IMM(BPF_REG_6, -1), + BPF_MOV64_IMM(BPF_REG_7, -1), + BPF_MOV64_IMM(BPF_REG_8, -1), + /* Store both R9 and R10 with BPF_B and read back. */ + BPF_STX_MEM(BPF_B, BPF_REG_1, BPF_REG_10, 0), + BPF_LDX_MEM(BPF_B, BPF_REG_2, BPF_REG_1, 0), + BPF_STX_MEM(BPF_B, BPF_REG_1, BPF_REG_9, 0), + BPF_LDX_MEM(BPF_B, BPF_REG_3, BPF_REG_1, 0), + /* Should read back as same value. */ + BPF_JMP_REG(BPF_JEQ, BPF_REG_2, BPF_REG_3, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_MOV64_IMM(BPF_REG_0, 42), + BPF_EXIT_INSN(), + }, + .fixup_map_array_48b = { 3 }, + .result = ACCEPT, + .retval = 42, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +},