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Mon, 06 Jul 2020 10:28:14 -0700 (PDT) Received: from [192.168.1.4] ([177.194.48.209]) by smtp.googlemail.com with ESMTPSA id b10sm19074558qkh.124.2020.07.06.10.28.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Jul 2020 10:28:14 -0700 (PDT) To: Szabolcs Nagy , libc-alpha@sourceware.org Cc: Sudakshina Das References: From: Adhemerval Zanella Autocrypt: addr=adhemerval.zanella@linaro.org; prefer-encrypt=mutual; keydata= mQINBFcVGkoBEADiQU2x/cBBmAVf5C2d1xgz6zCnlCefbqaflUBw4hB/bEME40QsrVzWZ5Nq 8kxkEczZzAOKkkvv4pRVLlLn/zDtFXhlcvQRJ3yFMGqzBjofucOrmdYkOGo0uCaoJKPT186L NWp53SACXguFJpnw4ODI64ziInzXQs/rUJqrFoVIlrPDmNv/LUv1OVPKz20ETjgfpg8MNwG6 iMizMefCl+RbtXbIEZ3TE/IaDT/jcOirjv96lBKrc/pAL0h/O71Kwbbp43fimW80GhjiaN2y WGByepnkAVP7FyNarhdDpJhoDmUk9yfwNuIuESaCQtfd3vgKKuo6grcKZ8bHy7IXX1XJj2X/ BgRVhVgMHAnDPFIkXtP+SiarkUaLjGzCz7XkUn4XAGDskBNfbizFqYUQCaL2FdbW3DeZqNIa nSzKAZK7Dm9+0VVSRZXP89w71Y7JUV56xL/PlOE+YKKFdEw+gQjQi0e+DZILAtFjJLoCrkEX w4LluMhYX/X8XP6/C3xW0yOZhvHYyn72sV4yJ1uyc/qz3OY32CRy+bwPzAMAkhdwcORA3JPb kPTlimhQqVgvca8m+MQ/JFZ6D+K7QPyvEv7bQ7M+IzFmTkOCwCJ3xqOD6GjX3aphk8Sr0dq3 4Awlf5xFDAG8dn8Uuutb7naGBd/fEv6t8dfkNyzj6yvc4jpVxwARAQABtElBZGhlbWVydmFs IFphbmVsbGEgTmV0dG8gKExpbmFybyBWUE4gS2V5KSA8YWRoZW1lcnZhbC56YW5lbGxhQGxp bmFyby5vcmc+iQI3BBMBCAAhBQJXFRpKAhsDBQsJCAcDBRUKCQgLBRYCAwEAAh4BAheAAAoJ EKqx7BSnlIjv0e8P/1YOYoNkvJ+AJcNUaM5a2SA9oAKjSJ/M/EN4Id5Ow41ZJS4lUA0apSXW NjQg3VeVc2RiHab2LIB4MxdJhaWTuzfLkYnBeoy4u6njYcaoSwf3g9dSsvsl3mhtuzm6aXFH /Qsauav77enJh99tI4T+58rp0EuLhDsQbnBic/ukYNv7sQV8dy9KxA54yLnYUFqH6pfH8Lly sTVAMyi5Fg5O5/hVV+Z0Kpr+ZocC1YFJkTsNLAW5EIYSP9ftniqaVsim7MNmodv/zqK0IyDB GLLH1kjhvb5+6ySGlWbMTomt/or/uvMgulz0bRS+LUyOmlfXDdT+t38VPKBBVwFMarNuREU2 69M3a3jdTfScboDd2ck1u7l+QbaGoHZQ8ZNUrzgObltjohiIsazqkgYDQzXIMrD9H19E+8fw kCNUlXxjEgH/Kg8DlpoYJXSJCX0fjMWfXywL6ZXc2xyG/hbl5hvsLNmqDpLpc1CfKcA0BkK+ k8R57fr91mTCppSwwKJYO9T+8J+o4ho/CJnK/jBy1pWKMYJPvvrpdBCWq3MfzVpXYdahRKHI ypk8m4QlRlbOXWJ3TDd/SKNfSSrWgwRSg7XCjSlR7PNzNFXTULLB34sZhjrN6Q8NQZsZnMNs TX8nlGOVrKolnQPjKCLwCyu8PhllU8OwbSMKskcD1PSkG6h3r0AquQINBFcVGkoBEACgAdbR Ck+fsfOVwT8zowMiL3l9a2DP3Eeak23ifdZG+8Avb/SImpv0UMSbRfnw/N81IWwlbjkjbGTu oT37iZHLRwYUFmA8fZX0wNDNKQUUTjN6XalJmvhdz9l71H3WnE0wneEM5ahu5V1L1utUWTyh VUwzX1lwJeV3vyrNgI1kYOaeuNVvq7npNR6t6XxEpqPsNc6O77I12XELic2+36YibyqlTJIQ V1SZEbIy26AbC2zH9WqaKyGyQnr/IPbTJ2Lv0dM3RaXoVf+CeK7gB2B+w1hZummD21c1Laua +VIMPCUQ+EM8W9EtX+0iJXxI+wsztLT6vltQcm+5Q7tY+HFUucizJkAOAz98YFucwKefbkTp eKvCfCwiM1bGatZEFFKIlvJ2QNMQNiUrqJBlW9nZp/k7pbG3oStOjvawD9ZbP9e0fnlWJIsj 6c7pX354Yi7kxIk/6gREidHLLqEb/otuwt1aoMPg97iUgDV5mlNef77lWE8vxmlY0FBWIXuZ yv0XYxf1WF6dRizwFFbxvUZzIJp3spAao7jLsQj1DbD2s5+S1BW09A0mI/1DjB6EhNN+4bDB SJCOv/ReK3tFJXuj/HbyDrOdoMt8aIFbe7YFLEExHpSk+HgN05Lg5TyTro8oW7TSMTk+8a5M kzaH4UGXTTBDP/g5cfL3RFPl79ubXwARAQABiQIfBBgBCAAJBQJXFRpKAhsMAAoJEKqx7BSn lIjvI/8P/jg0jl4Tbvg3B5kT6PxJOXHYu9OoyaHLcay6Cd+ZrOd1VQQCbOcgLFbf4Yr+rE9l mYsY67AUgq2QKmVVbn9pjvGsEaz8UmfDnz5epUhDxC6yRRvY4hreMXZhPZ1pbMa6A0a/WOSt AgFj5V6Z4dXGTM/lNManr0HjXxbUYv2WfbNt3/07Db9T+GZkpUotC6iknsTA4rJi6u2ls0W9 1UIvW4o01vb4nZRCj4rni0g6eWoQCGoVDk/xFfy7ZliR5B+3Z3EWRJcQskip/QAHjbLa3pml xAZ484fVxgeESOoaeC9TiBIp0NfH8akWOI0HpBCiBD5xaCTvR7ujUWMvhsX2n881r/hNlR9g fcE6q00qHSPAEgGr1bnFv74/1vbKtjeXLCcRKk3Ulw0bY1OoDxWQr86T2fZGJ/HIZuVVBf3+ gaYJF92GXFynHnea14nFFuFgOni0Mi1zDxYH/8yGGBXvo14KWd8JOW0NJPaCDFJkdS5hu0VY 7vJwKcyHJGxsCLU+Et0mryX8qZwqibJIzu7kUJQdQDljbRPDFd/xmGUFCQiQAncSilYOcxNU EMVCXPAQTteqkvA+gNqSaK1NM9tY0eQ4iJpo+aoX8HAcn4sZzt2pfUB9vQMTBJ2d4+m/qO6+ cFTAceXmIoFsN8+gFN3i8Is3u12u8xGudcBPvpoy4OoG Subject: Re: [PATCH v6 08/14] aarch64: enable BTI at runtime Message-ID: <4a8dae93-b9d3-9d8a-069a-f5c87ac30cf0@linaro.org> Date: Mon, 6 Jul 2020 14:28:12 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-14.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 06 Jul 2020 17:28:17 -0000 On 01/07/2020 11:39, Szabolcs Nagy wrote: > From: Sudakshina Das > > Binaries can opt-in to using BTI via an ELF object file marking. > The dynamic linker has to then mprotect the executable segments > with PROT_BTI. In case of static linked executables or in case > of the dynamic linker itself, PROT_BTI protection is done by the > operating system. > > On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check > the properties of a binary because PT_NOTE can be unreliable with > old linkers (old linkers just append the notes of input objects > together and add them to the output without checking them for > consistency which means multiple incompatible GNU property notes > can be present in PT_NOTE). > > BTI property is handled in the loader even if glibc is not built > with BTI support, so in theory user code can be BTI protected > independently of glibc. In practice though user binaries are not > marked with the BTI property if glibc has no support because the > static linked libc objects (crt files, libc_nonshared.a) are > unmarked. > > This patch relies on Linux userspace API that is not yet in a > linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. > > Co-authored-by: Szabolcs Nagy LGTM, with a jsut nit below. Reviewed-by: Adhemerval Zanella > --- > sysdeps/aarch64/Makefile | 4 ++ > sysdeps/aarch64/dl-bti.c | 54 ++++++++++++++++ > sysdeps/aarch64/dl-prop.h | 63 +++++++++++++++++++ > sysdeps/aarch64/linkmap.h | 3 + > sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h | 1 + > sysdeps/unix/sysv/linux/aarch64/bits/mman.h | 31 +++++++++ > .../unix/sysv/linux/aarch64/cpu-features.c | 3 + > .../unix/sysv/linux/aarch64/cpu-features.h | 2 + > 8 files changed, 161 insertions(+) > create mode 100644 sysdeps/aarch64/dl-bti.c > create mode 100644 sysdeps/aarch64/dl-prop.h > create mode 100644 sysdeps/unix/sysv/linux/aarch64/bits/mman.h > > diff --git a/sysdeps/aarch64/Makefile b/sysdeps/aarch64/Makefile > index 9cb141004d..5ae8b082b0 100644 > --- a/sysdeps/aarch64/Makefile > +++ b/sysdeps/aarch64/Makefile > @@ -1,5 +1,9 @@ > long-double-fcts = yes > > +ifeq ($(subdir),elf) > +sysdep-dl-routines += dl-bti > +endif > + > ifeq ($(subdir),elf) > sysdep-dl-routines += tlsdesc dl-tlsdesc > gen-as-const-headers += dl-link.sym Ok. > diff --git a/sysdeps/aarch64/dl-bti.c b/sysdeps/aarch64/dl-bti.c > new file mode 100644 > index 0000000000..3c92377cc8 > --- /dev/null > +++ b/sysdeps/aarch64/dl-bti.c > @@ -0,0 +1,54 @@ > +/* AArch64 BTI functions. > + Copyright (C) 2020 Free Software Foundation, Inc. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#include > +#include > +#include > +#include > + > +static int > +enable_bti (struct link_map *map, const char *program) > +{ > + const ElfW(Phdr) *phdr; > + unsigned prot = PROT_READ | PROT_EXEC | PROT_BTI; > + > + for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr) > + if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X)) > + { > + ElfW(Addr) start = phdr->p_vaddr + map->l_addr; > + ElfW(Addr) len = phdr->p_memsz; I don't think ElfW(Addr) is the correct type here (although it will be mapped to uint64_t anyway). Why not use size_t here since the idea is really to use on __mprotect? > + if (__mprotect ((void *) start, len, prot) < 0) > + { > + if (program) > + _dl_fatal_printf ("%s: mprotect failed to turn on BTI\n", > + map->l_name); > + else > + _dl_signal_error (errno, map->l_name, "dlopen", > + N_("mprotect failed to turn on BTI")); > + } > + } > + return 0; > +} > + > +/* Enable BTI for L if required. */ > + > +void > +_dl_bti_check (struct link_map *l, const char *program) > +{ > + if (GLRO(dl_aarch64_cpu_features).bti && l->l_mach.bti) > + enable_bti (l, program); > +} Ok. > diff --git a/sysdeps/aarch64/dl-prop.h b/sysdeps/aarch64/dl-prop.h > new file mode 100644 > index 0000000000..b0785bda83 > --- /dev/null > +++ b/sysdeps/aarch64/dl-prop.h > @@ -0,0 +1,63 @@ > +/* Support for GNU properties. AArch64 version. > + Copyright (C) 2018-2020 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#ifndef _DL_PROP_H > +#define _DL_PROP_H > + > +extern void _dl_bti_check (struct link_map *, const char *) > + attribute_hidden; > + > +static inline void __attribute__ ((always_inline)) > +_rtld_main_check (struct link_map *m, const char *program) > +{ > + _dl_bti_check (m, program); > +} > + > +static inline void __attribute__ ((always_inline)) > +_dl_open_check (struct link_map *m) > +{ > + _dl_bti_check (m, NULL); > +} > + > +static inline void __attribute__ ((always_inline)) > +_dl_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph) > +{ > +} > + > +static inline int > +_dl_process_gnu_property (struct link_map *l, uint32_t type, uint32_t datasz, > + void *data) > +{ > + if (type == GNU_PROPERTY_AARCH64_FEATURE_1_AND) > + { > + /* Stop if the property note is ill-formed. */ > + if (datasz != 4) > + return 0; > + > + unsigned int feature_1 = *(unsigned int *) data; > + if (feature_1 & GNU_PROPERTY_AARCH64_FEATURE_1_BTI) > + l->l_mach.bti = true; > + > + /* Stop if we processed the property note. */ > + return 0; > + } > + /* Continue. */ > + return 1; > +} > + > +#endif /* _DL_PROP_H */ Ok. > diff --git a/sysdeps/aarch64/linkmap.h b/sysdeps/aarch64/linkmap.h > index 943a9ee9e4..847a03ace2 100644 > --- a/sysdeps/aarch64/linkmap.h > +++ b/sysdeps/aarch64/linkmap.h > @@ -16,8 +16,11 @@ > License along with the GNU C Library; if not, see > . */ > > +#include > + > struct link_map_machine > { > ElfW(Addr) plt; /* Address of .plt */ > void *tlsdesc_table; /* Address of TLS descriptor hash table. */ > + bool bti; /* Branch Target Identification is enabled. */ > }; Ok. > diff --git a/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h b/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h > index 4ee14b4208..af90d8a626 100644 > --- a/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h > +++ b/sysdeps/unix/sysv/linux/aarch64/bits/hwcap.h > @@ -72,3 +72,4 @@ > #define HWCAP2_BF16 (1 << 14) > #define HWCAP2_DGH (1 << 15) > #define HWCAP2_RNG (1 << 16) > +#define HWCAP2_BTI (1 << 17) Ok. > diff --git a/sysdeps/unix/sysv/linux/aarch64/bits/mman.h b/sysdeps/unix/sysv/linux/aarch64/bits/mman.h > new file mode 100644 > index 0000000000..ecae046344 > --- /dev/null > +++ b/sysdeps/unix/sysv/linux/aarch64/bits/mman.h > @@ -0,0 +1,31 @@ > +/* Definitions for POSIX memory map interface. Linux/AArch64 version. > + Copyright (C) 2020 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#ifndef _SYS_MMAN_H > +# error "Never use directly; include instead." > +#endif > + > +/* AArch64 specific definitions, should be in sync with > + arch/arm64/include/uapi/asm/mman.h. */ > + > +#define PROT_BTI 0x10 > + > +#include > + > +/* Include generic Linux declarations. */ > +#include Ok. > diff --git a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c > index 896c588fee..b9ab827aca 100644 > --- a/sysdeps/unix/sysv/linux/aarch64/cpu-features.c > +++ b/sysdeps/unix/sysv/linux/aarch64/cpu-features.c > @@ -83,4 +83,7 @@ init_cpu_features (struct cpu_features *cpu_features) > > if ((dczid & DCZID_DZP_MASK) == 0) > cpu_features->zva_size = 4 << (dczid & DCZID_BS_MASK); > + > + /* Check if BTI is supported. */ > + cpu_features->bti = GLRO (dl_hwcap2) & HWCAP2_BTI; > } Ok. > diff --git a/sysdeps/unix/sysv/linux/aarch64/cpu-features.h b/sysdeps/unix/sysv/linux/aarch64/cpu-features.h > index 1389cea1b3..a81f186ec2 100644 > --- a/sysdeps/unix/sysv/linux/aarch64/cpu-features.h > +++ b/sysdeps/unix/sysv/linux/aarch64/cpu-features.h > @@ -20,6 +20,7 @@ > #define _CPU_FEATURES_AARCH64_H > > #include > +#include > > #define MIDR_PARTNUM_SHIFT 4 > #define MIDR_PARTNUM_MASK (0xfff << MIDR_PARTNUM_SHIFT) > @@ -64,6 +65,7 @@ struct cpu_features > { > uint64_t midr_el1; > unsigned zva_size; > + bool bti; > }; > > #endif /* _CPU_FEATURES_AARCH64_H */ > Ok.