ffaae70936
Each TLSDESC relocation relocates a 2-word descriptor in the GOT that contains: - the address of a TLS resolver function - an argument to pass (indirectly) to the resolver function (Specifically, the address of the 2-word descriptor is passed to the resolver.) The loader resolves R_GENERIC_TLSDESC relocations using one of three resolver functions that it defines: - tlsdesc_resolver_static - tlsdesc_resolver_dynamic - tlsdesc_resolver_unresolved_weak The resolver functions are written in assembly because they have a restrictive calling convention. They're only allowed to modify x0 and (apparently) the condition codes. For a relocation to memory in static TLS (i.e. the executable or an solib loaded initially), the loader uses a simple resolver function, tlsdesc_resolver_static, that returns the static offset it receives from the loader. For relocations to dynamic TLS memory (i.e. memory in a dlopen'ed solib), the loader uses tlsdesc_resolver_dynamic, which allocates TLS memory on demand. It inlines the fast path of __tls_get_addr, then falls back to __tls_get_addr when it needs to allocate memory. The loader handles these dynamic TLS relocations in two passes: - In the first pass, it allocates a table of TlsDynamicResolverArg objects, one per dynamic TLSDESC relocation. - In the second pass, once the table is finalized, it writes the addresses of the TlsDynamicResolverArg objects into the TLSDESC relocations. tlsdesc_resolver_unresolved_weak returns a negated thread pointer so that taking the address of an unresolved weak TLS symbols produces NULL. The loader handles R_GENERIC_TLSDESC in a target-independent way, but only for arm64, because Bionic has only implemented the resolver functions for arm64. Bug: http://b/78026329 Test: bionic unit tests Test: check that backtrace works inside a resolver function and inside __tls_get_addr called from a resolver (gdbclient.py, b __tls_get_addr, bt) Merged-In: I752e59ff986292449892c449dad2546e6f0ff7b6 Change-Id: I752e59ff986292449892c449dad2546e6f0ff7b6
65 lines
2.2 KiB
C
65 lines
2.2 KiB
C
/*
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* Copyright (C) 2019 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#pragma once
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#include <stdlib.h>
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#include "private/bionic_elf_tls.h"
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struct TlsModule;
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struct soinfo;
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void linker_setup_exe_static_tls(const char* progname);
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void linker_finalize_static_tls();
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void register_soinfo_tls(soinfo* si);
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void unregister_soinfo_tls(soinfo* si);
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const TlsModule& get_tls_module(size_t module_id);
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typedef size_t TlsDescResolverFunc(size_t);
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struct TlsDescriptor {
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#if defined(__arm__)
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size_t arg;
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TlsDescResolverFunc* func;
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#else
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TlsDescResolverFunc* func;
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size_t arg;
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#endif
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};
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struct TlsDynamicResolverArg {
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size_t generation;
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TlsIndex index;
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};
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__LIBC_HIDDEN__ extern "C" size_t tlsdesc_resolver_static(size_t);
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__LIBC_HIDDEN__ extern "C" size_t tlsdesc_resolver_dynamic(size_t);
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__LIBC_HIDDEN__ extern "C" size_t tlsdesc_resolver_unresolved_weak(size_t);
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