From patchwork Tue Jul 12 14:39:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Dobriyan X-Patchwork-Id: 12915060 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 E1D0DC433EF for ; Tue, 12 Jul 2022 14:39:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233171AbiGLOjO (ORCPT ); Tue, 12 Jul 2022 10:39:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59132 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230113AbiGLOjN (ORCPT ); Tue, 12 Jul 2022 10:39:13 -0400 Received: from mail-ej1-x62b.google.com (mail-ej1-x62b.google.com [IPv6:2a00:1450:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61D492495E; Tue, 12 Jul 2022 07:39:12 -0700 (PDT) Received: by mail-ej1-x62b.google.com with SMTP id mf4so13509996ejc.3; Tue, 12 Jul 2022 07:39:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:mime-version:content-disposition; bh=MkimO/JYfFEWErwwRlGZI0yEI3KTdQ++omf5SZxftc4=; b=kBVAhs7SuDDu7URHr0MlshT8v64mj4buHFbV/4Rbh3RrmSkwTHDt/+porNaTfhjeFR xQOmNyrpXOnrt8deh+kv+2VUxxwjT+BKXdjUI8+V4u3t+40qiOkj5c/o/twvWDLnuDPL mD1BhRtPWDZ4ZqOHWJHDqSLGcdP+R5rjEH0bxu8I4uaAmrxonjwyid8CLhkI3RbjPeF8 fBke5NR6KZUfvlPwGMJHOUFx9Y7v20jN+kibypMCu8Mt/RMIwavyux3ZxxnsuIQw/XW5 Augm2qz4Ec/06nsrp5NMYBbRDmHDyzIG+65HY5RehskEXxqmsOPLbLzi2Z0/TFKdocI3 zrTg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition; bh=MkimO/JYfFEWErwwRlGZI0yEI3KTdQ++omf5SZxftc4=; b=WYG/PCHS51lHr1DFIMdNVTgZ/YOL7CsTtX9I46/RMBqXxT5R2XYyktMZgIAaIHHX03 r8DP9JhpU4EWrxrUDylsc5XKYG5+Rrec2z7d/ws7QIUCapOlswxuYJELHUx8mEwEqJqD OW87unmtyydtMW2jmPi3OeOYPVWPYwj7WY9+hRrd6t35eyHwGibrsmGkaeBtbYzF4zHc rh7ixEFjqVuRk1WXt3z/S0gk0qs7fHq1DOHaWexx5zGsjpFzZapFOMZ/oBFXDtww3hxy seqUXA/CP0LBREP2em0SXRhQYun2i2z7vOonHong2DYhGsASD1UH8khx6f3d2KJlOquR Z2yg== X-Gm-Message-State: AJIora/1rKolZ8GEdCfnMtK8jKnhIgcXtNCdEmg7Xvfzlxh9k3PjS2b7 exeOWHPzr8T6VSkg9SAv7A== X-Google-Smtp-Source: AGRyM1sFrjxb8Xrs4zv78FZe/7YJyrbgXHAoRlUjqwvCnWRK+PDXIDo+aqby0XL2zc8NS68689prlw== X-Received: by 2002:a17:906:7b82:b0:6f3:ee8d:b959 with SMTP id s2-20020a1709067b8200b006f3ee8db959mr24608884ejo.458.1657636750966; Tue, 12 Jul 2022 07:39:10 -0700 (PDT) Received: from localhost.localdomain ([46.53.253.195]) by smtp.gmail.com with ESMTPSA id 18-20020a170906211200b006feec47dae9sm3861670ejt.157.2022.07.12.07.39.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Jul 2022 07:39:09 -0700 (PDT) Date: Tue, 12 Jul 2022 17:39:07 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, dylanbhatch@google.com, skhan@linuxfoundation.org Subject: [PATCH] proc: fix test for "vsyscall=xonly" boot option Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Booting with vsyscall=xonly results in the "--xp" vsyscall VMA: ffffffffff600000-ffffffffff601000 --xp ... [vsyscall]\n Test does read from fixed vsyscall address to determine if kernel supports vsyscall page but it doesn't work with vsyscall=xonly because, well, vsyscall page is execute only. Fix test by trying to execute from the first byte of the page (which contains gettimeofday() stub). This should work because vsyscall entry points themselves have stable addresses by design. Alexey, avoiding parsing .config, /proc/config.gz and /proc/cmdline at all costs. Signed-off-by: Alexey Dobriyan --- I'm not sure who reported what, so please add tested-by and reported-by lines. tools/testing/selftests/proc/proc-pid-vm.c | 75 ++++++++++++++++++++++++++--- 1 file changed, 68 insertions(+), 7 deletions(-) --- a/tools/testing/selftests/proc/proc-pid-vm.c +++ b/tools/testing/selftests/proc/proc-pid-vm.c @@ -211,10 +211,19 @@ static int make_exe(const uint8_t *payload, size_t len) } #endif -static bool g_vsyscall = false; +/* + * 0: vsyscall VMA doesn't exist vsyscall=none + * 1: vsyscall VMA is r-xp vsyscall=emulate + * 2: vsyscall VMA is --xp vsyscall=xonly + */ +static int g_vsyscall; +static const char *str_vsyscall; -static const char str_vsyscall[] = +static const char str_vsyscall_0[] = ""; +static const char str_vsyscall_1[] = "ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n"; +static const char str_vsyscall_2[] = +"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n"; #ifdef __x86_64__ static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___) @@ -223,13 +232,47 @@ static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___) } /* - * vsyscall page can't be unmapped, probe it with memory load. + * vsyscall page can't be unmapped, probe it directly. */ static void vsyscall(void) { pid_t pid; int wstatus; + pid = fork(); + if (pid < 0) { + fprintf(stderr, "fork, errno %d\n", errno); + exit(1); + } + if (pid == 0) { + struct rlimit rlim = {0, 0}; + (void)setrlimit(RLIMIT_CORE, &rlim); + + /* Hide "segfault at ffffffffff600000" messages. */ + struct sigaction act; + memset(&act, 0, sizeof(struct sigaction)); + act.sa_flags = SA_SIGINFO; + act.sa_sigaction = sigaction_SIGSEGV; + (void)sigaction(SIGSEGV, &act, NULL); + + /* gettimeofday(NULL, NULL); */ + asm volatile ( + "call %P0" + : + : "i" (0xffffffffff600000), "D" (NULL), "S" (NULL) + : "rax" + ); + exit(0); + } + waitpid(pid, &wstatus, 0); + if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0) { + /* vsyscall page exists and is executable. */ + } else { + /* vsyscall page doesn't exist. */ + g_vsyscall = 0; + return; + } + pid = fork(); if (pid < 0) { fprintf(stderr, "fork, errno %d\n", errno); @@ -251,8 +294,13 @@ static void vsyscall(void) } waitpid(pid, &wstatus, 0); if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0) { - g_vsyscall = true; + /* vsyscall page is readable and executable. */ + g_vsyscall = 1; + return; } + + /* vsyscall page is executable but unreadable. */ + g_vsyscall = 2; } int main(void) @@ -261,6 +309,19 @@ int main(void) int exec_fd; vsyscall(); + switch (g_vsyscall) { + case 0: + str_vsyscall = str_vsyscall_0; + break; + case 1: + str_vsyscall = str_vsyscall_1; + break; + case 2: + str_vsyscall = str_vsyscall_2; + break; + default: + abort(); + } atexit(ate); @@ -314,7 +375,7 @@ int main(void) /* Test /proc/$PID/maps */ { - const size_t len = strlen(buf0) + (g_vsyscall ? strlen(str_vsyscall) : 0); + const size_t len = strlen(buf0) + strlen(str_vsyscall); char buf[256]; ssize_t rv; int fd; @@ -327,7 +388,7 @@ int main(void) rv = read(fd, buf, sizeof(buf)); assert(rv == len); assert(memcmp(buf, buf0, strlen(buf0)) == 0); - if (g_vsyscall) { + if (g_vsyscall > 0) { assert(memcmp(buf + strlen(buf0), str_vsyscall, strlen(str_vsyscall)) == 0); } } @@ -374,7 +435,7 @@ int main(void) assert(memmem(buf, rv, S[i], strlen(S[i]))); } - if (g_vsyscall) { + if (g_vsyscall > 0) { assert(memmem(buf, rv, str_vsyscall, strlen(str_vsyscall))); } }