From nobody Thu Apr 2 19:51:42 2026 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 5367DC6FA90 for ; Wed, 21 Sep 2022 19:38:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229563AbiIUTiG (ORCPT ); Wed, 21 Sep 2022 15:38:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229777AbiIUTiC (ORCPT ); Wed, 21 Sep 2022 15:38:02 -0400 X-Greylist: delayed 770 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Wed, 21 Sep 2022 12:37:59 PDT Received: from barracuda.ebox.ca (barracuda.ebox.ca [96.127.255.19]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 31E619E125 for ; Wed, 21 Sep 2022 12:37:59 -0700 (PDT) X-ASG-Debug-ID: 1663788304-0c856e13fd3500c0001-xx1T2L Received: from smtp.ebox.ca (smtp.ebox.ca [96.127.255.82]) by barracuda.ebox.ca with ESMTP id 7NwNW7ODnS8we0ux (version=TLSv1 cipher=AES128-SHA bits=128 verify=NO); Wed, 21 Sep 2022 15:25:04 -0400 (EDT) X-Barracuda-Envelope-From: mathieu.desnoyers@efficios.com X-Barracuda-RBL-Trusted-Forwarder: 96.127.255.82 Received: from localhost.localdomain (192-222-180-24.qc.cable.ebox.net [192.222.180.24]) by smtp.ebox.ca (Postfix) with ESMTP id 1B1DB441D65; Wed, 21 Sep 2022 15:25:04 -0400 (EDT) From: Mathieu Desnoyers X-Barracuda-RBL-IP: 192.222.180.24 X-Barracuda-Effective-Source-IP: 192-222-180-24.qc.cable.ebox.net[192.222.180.24] X-Barracuda-Apparent-Source-IP: 192.222.180.24 To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , "Paul E . McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, Christian Brauner , Florian Weimer , David.Laight@ACULAB.COM, carlos@redhat.com, Peter Oskolkov , Alexander Mikhalitsyn , Mathieu Desnoyers Subject: [RFC PATCH v4 04/25] selftests/rseq: Use ELF auxiliary vector for extensible rseq Date: Wed, 21 Sep 2022 15:24:33 -0400 X-ASG-Orig-Subj: [RFC PATCH v4 04/25] selftests/rseq: Use ELF auxiliary vector for extensible rseq Message-Id: <20220921192454.231662-5-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220921192454.231662-1-mathieu.desnoyers@efficios.com> References: <20220921192454.231662-1-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Barracuda-Connect: smtp.ebox.ca[96.127.255.82] X-Barracuda-Start-Time: 1663788304 X-Barracuda-Encrypted: AES128-SHA X-Barracuda-URL: https://96.127.255.19:443/cgi-mod/mark.cgi X-Virus-Scanned: by bsmtpd at ebox.ca X-Barracuda-Scan-Msg-Size: 6186 X-Barracuda-BRTS-Status: 1 X-Barracuda-Spam-Score: 0.50 X-Barracuda-Spam-Status: No, SCORE=0.50 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=5.0 tests=BSF_RULE7568M X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.3.100943 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- 0.50 BSF_RULE7568M Custom Rule 7568M Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Use the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE to detect the RSEQ features supported by the kernel. Signed-off-by: Mathieu Desnoyers --- tools/testing/selftests/rseq/rseq-abi.h | 5 ++ tools/testing/selftests/rseq/rseq.c | 68 ++++++++++++++++++++++--- tools/testing/selftests/rseq/rseq.h | 18 +++++-- 3 files changed, 79 insertions(+), 12 deletions(-) diff --git a/tools/testing/selftests/rseq/rseq-abi.h b/tools/testing/selfte= sts/rseq/rseq-abi.h index a8c44d9af71f..00ac846d85b0 100644 --- a/tools/testing/selftests/rseq/rseq-abi.h +++ b/tools/testing/selftests/rseq/rseq-abi.h @@ -146,6 +146,11 @@ struct rseq_abi { * this thread. */ __u32 flags; + + /* + * Flexible array member at end of structure, after last feature field. + */ + char end[]; } __attribute__((aligned(4 * sizeof(__u64)))); =20 #endif /* _RSEQ_ABI_H */ diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/= rseq/rseq.c index 986b9458efb2..20ea536d1012 100644 --- a/tools/testing/selftests/rseq/rseq.c +++ b/tools/testing/selftests/rseq/rseq.c @@ -28,6 +28,8 @@ #include #include #include +#include +#include =20 #include "../kselftest.h" #include "rseq.h" @@ -36,20 +38,38 @@ static const ptrdiff_t *libc_rseq_offset_p; static const unsigned int *libc_rseq_size_p; static const unsigned int *libc_rseq_flags_p; =20 -/* Offset from the thread pointer to the rseq area. */ +/* Offset from the thread pointer to the rseq area. */ ptrdiff_t rseq_offset; =20 -/* Size of the registered rseq area. 0 if the registration was - unsuccessful. */ +/* + * Size of the registered rseq area. 0 if the registration was + * unsuccessful. + */ unsigned int rseq_size =3D -1U; =20 /* Flags used during rseq registration. */ unsigned int rseq_flags; =20 +/* + * rseq feature size supported by the kernel. 0 if the registration was + * unsuccessful. + */ +unsigned int rseq_feature_size =3D -1U; + static int rseq_ownership; +static int rseq_reg_success; /* At least one rseq registration has succede= d. */ + +/* Allocate a large area for the TLS. */ +#define RSEQ_THREAD_AREA_ALLOC_SIZE 1024 + +/* Original struct rseq feature size is 20 bytes. */ +#define ORIG_RSEQ_FEATURE_SIZE 20 + +/* Orignal struct rseq allocation size is 32 bytes. */ +#define ORIG_RSEQ_ALLOC_SIZE 32 =20 static -__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec= "))) =3D { +__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec= "), aligned(RSEQ_THREAD_AREA_ALLOC_SIZE))) =3D { .cpu_id =3D RSEQ_ABI_CPU_ID_UNINITIALIZED, }; =20 @@ -84,10 +104,18 @@ int rseq_register_current_thread(void) /* Treat libc's ownership as a successful registration. */ return 0; } - rc =3D sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), 0, RSEQ_SIG); - if (rc) + rc =3D sys_rseq(&__rseq_abi, rseq_size, 0, RSEQ_SIG); + if (rc) { + if (RSEQ_READ_ONCE(rseq_reg_success)) { + /* Incoherent success/failure within process. */ + abort(); + } + rseq_size =3D 0; + rseq_feature_size =3D 0; return -1; + } assert(rseq_current_cpu_raw() >=3D 0); + RSEQ_WRITE_ONCE(rseq_reg_success, 1); return 0; } =20 @@ -99,12 +127,28 @@ int rseq_unregister_current_thread(void) /* Treat libc's ownership as a successful unregistration. */ return 0; } - rc =3D sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), RSEQ_ABI_FLAG_UNREG= ISTER, RSEQ_SIG); + rc =3D sys_rseq(&__rseq_abi, rseq_size, RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SI= G); if (rc) return -1; return 0; } =20 +static +unsigned int get_rseq_feature_size(void) +{ + unsigned long auxv_rseq_feature_size, auxv_rseq_align; + + auxv_rseq_align =3D getauxval(AT_RSEQ_ALIGN); + assert(!auxv_rseq_align || auxv_rseq_align <=3D RSEQ_THREAD_AREA_ALLOC_SI= ZE); + + auxv_rseq_feature_size =3D getauxval(AT_RSEQ_FEATURE_SIZE); + assert(!auxv_rseq_feature_size || auxv_rseq_feature_size <=3D RSEQ_THREAD= _AREA_ALLOC_SIZE); + if (auxv_rseq_feature_size) + return auxv_rseq_feature_size; + else + return ORIG_RSEQ_FEATURE_SIZE; +} + static __attribute__((constructor)) void rseq_init(void) { @@ -116,14 +160,21 @@ void rseq_init(void) rseq_offset =3D *libc_rseq_offset_p; rseq_size =3D *libc_rseq_size_p; rseq_flags =3D *libc_rseq_flags_p; + rseq_feature_size =3D get_rseq_feature_size(); + if (rseq_feature_size > rseq_size) + rseq_feature_size =3D rseq_size; return; } if (!rseq_available()) return; rseq_ownership =3D 1; rseq_offset =3D (void *)&__rseq_abi - rseq_thread_pointer(); - rseq_size =3D sizeof(struct rseq_abi); rseq_flags =3D 0; + rseq_feature_size =3D get_rseq_feature_size(); + if (rseq_feature_size =3D=3D ORIG_RSEQ_FEATURE_SIZE) + rseq_size =3D ORIG_RSEQ_ALLOC_SIZE; + else + rseq_size =3D RSEQ_THREAD_AREA_ALLOC_SIZE; } =20 static __attribute__((destructor)) @@ -133,6 +184,7 @@ void rseq_exit(void) return; rseq_offset =3D 0; rseq_size =3D -1U; + rseq_feature_size =3D -1U; rseq_ownership =3D 0; } =20 diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/= rseq/rseq.h index 6f7513384bf5..95adc1e1b0db 100644 --- a/tools/testing/selftests/rseq/rseq.h +++ b/tools/testing/selftests/rseq/rseq.h @@ -47,14 +47,24 @@ =20 #include "rseq-thread-pointer.h" =20 -/* Offset from the thread pointer to the rseq area. */ +/* Offset from the thread pointer to the rseq area. */ extern ptrdiff_t rseq_offset; -/* Size of the registered rseq area. 0 if the registration was - unsuccessful. */ + +/* + * Size of the registered rseq area. 0 if the registration was + * unsuccessful. + */ extern unsigned int rseq_size; -/* Flags used during rseq registration. */ + +/* Flags used during rseq registration. */ extern unsigned int rseq_flags; =20 +/* + * rseq feature size supported by the kernel. 0 if the registration was + * unsuccessful. + */ +extern unsigned int rseq_feature_size; + static inline struct rseq_abi *rseq_get_abi(void) { return (struct rseq_abi *) ((uintptr_t) rseq_thread_pointer() + rseq_offs= et); --=20 2.25.1