From patchwork Fri Jul 20 18:05:54 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "H.J. Lu" X-Patchwork-Id: 28534 Received: (qmail 20640 invoked by alias); 20 Jul 2018 18:06:14 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 20533 invoked by uid 89); 20 Jul 2018 18:06:13 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-25.5 required=5.0 tests=AWL, BAYES_00, FREEMAIL_FROM, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, SPF_SOFTFAIL autolearn=ham version=3.3.2 spammy=Hx-languages-length:3593 X-HELO: mga05.intel.com From: "H.J. Lu" To: libc-alpha@sourceware.org Subject: [PATCH 2/3] x86: Rename __glibc_reserved2 to ssp_base in tcbhead_t Date: Fri, 20 Jul 2018 11:05:54 -0700 Message-Id: <20180720180555.101990-3-hjl.tools@gmail.com> In-Reply-To: <20180720180555.101990-1-hjl.tools@gmail.com> References: <20180720180555.101990-1-hjl.tools@gmail.com> This will be used to implement shadow stack switching by getcontext, makecontext, setcontext and swapcontext. * sysdeps/i386/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New. * sysdeps/i386/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2 with ssp_base. * sysdeps/x86_64/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New. * sysdeps/x86_64/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2 with ssp_base. --- sysdeps/i386/nptl/tcb-offsets.sym | 1 + sysdeps/i386/nptl/tls.h | 3 ++- sysdeps/x86_64/nptl/tcb-offsets.sym | 1 + sysdeps/x86_64/nptl/tls.h | 10 +++++++++- 4 files changed, 13 insertions(+), 2 deletions(-) diff --git a/sysdeps/i386/nptl/tcb-offsets.sym b/sysdeps/i386/nptl/tcb-offsets.sym index fbac241c45..2ec9e787c1 100644 --- a/sysdeps/i386/nptl/tcb-offsets.sym +++ b/sysdeps/i386/nptl/tcb-offsets.sym @@ -13,3 +13,4 @@ CLEANUP_PREV offsetof (struct _pthread_cleanup_buffer, __prev) MUTEX_FUTEX offsetof (pthread_mutex_t, __data.__lock) POINTER_GUARD offsetof (tcbhead_t, pointer_guard) FEATURE_1_OFFSET offsetof (tcbhead_t, feature_1) +SSP_BASE_OFFSET offsetof (tcbhead_t, ssp_base) diff --git a/sysdeps/i386/nptl/tls.h b/sysdeps/i386/nptl/tls.h index 21e23cd809..12285d3217 100644 --- a/sysdeps/i386/nptl/tls.h +++ b/sysdeps/i386/nptl/tls.h @@ -49,7 +49,8 @@ typedef struct void *__private_tm[3]; /* GCC split stack support. */ void *__private_ss; - void *__glibc_reserved2; + /* The lowest address of shadow stack, */ + unsigned long ssp_base; } tcbhead_t; /* morestack.S in libgcc uses offset 0x30 to access __private_ss, */ diff --git a/sysdeps/x86_64/nptl/tcb-offsets.sym b/sysdeps/x86_64/nptl/tcb-offsets.sym index 387621e88c..ae8034743b 100644 --- a/sysdeps/x86_64/nptl/tcb-offsets.sym +++ b/sysdeps/x86_64/nptl/tcb-offsets.sym @@ -13,6 +13,7 @@ MULTIPLE_THREADS_OFFSET offsetof (tcbhead_t, multiple_threads) POINTER_GUARD offsetof (tcbhead_t, pointer_guard) VGETCPU_CACHE_OFFSET offsetof (tcbhead_t, vgetcpu_cache) FEATURE_1_OFFSET offsetof (tcbhead_t, feature_1) +SSP_BASE_OFFSET offsetof (tcbhead_t, ssp_base) -- Not strictly offsets, but these values are also used in the TCB. TCB_CANCELSTATE_BITMASK CANCELSTATE_BITMASK diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h index f042a0250a..e88561c934 100644 --- a/sysdeps/x86_64/nptl/tls.h +++ b/sysdeps/x86_64/nptl/tls.h @@ -60,7 +60,8 @@ typedef struct void *__private_tm[4]; /* GCC split stack support. */ void *__private_ss; - long int __glibc_reserved2; + /* The lowest address of shadow stack, */ + unsigned long long int ssp_base; /* Must be kept even if it is no longer used by glibc since programs, like AddressSanitizer, depend on the size of tcbhead_t. */ __128bits __glibc_unused2[8][4] __attribute__ ((aligned (32))); @@ -72,10 +73,17 @@ typedef struct /* morestack.S in libgcc uses offset 0x40 to access __private_ss, */ _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x40, "offset of __private_ss != 0x40"); +/* NB: ssp_base used to be "long int __glibc_reserved2", which was + changed from 32 bits to 64 bits. Make sure that the offset of the + next field, __glibc_unused2, is unchanged. */ +_Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x60, + "offset of __glibc_unused2 != 0x60"); # else /* morestack.S in libgcc uses offset 0x70 to access __private_ss, */ _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x70, "offset of __private_ss != 0x70"); +_Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80, + "offset of __glibc_unused2 != 0x80"); # endif #else /* __ASSEMBLER__ */