platform_bionic/linker/linker_tls.h

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Reorganize static TLS memory for ELF TLS For ELF TLS "local-exec" accesses, the static linker assumes that an executable's TLS segment is located at a statically-known offset from the thread pointer (i.e. "variant 1" for ARM and "variant 2" for x86). Because these layouts are incompatible, Bionic generally needs to allocate its TLS slots differently between different architectures. To allow per-architecture TLS slots: - Replace the TLS_SLOT_xxx enumerators with macros. New ARM slots are generally negative, while new x86 slots are generally positive. - Define a bionic_tcb struct that provides two things: - a void* raw_slots_storage[BIONIC_TLS_SLOTS] field - an inline accessor function: void*& tls_slot(size_t tpindex); For ELF TLS, it's necessary to allocate a temporary TCB (i.e. TLS slots), because the runtime linker doesn't know how large the static TLS area is until after it has loaded all of the initial solibs. To accommodate Golang, it's necessary to allocate the pthread keys at a fixed, small, positive offset from the thread pointer. This CL moves the pthread keys into bionic_tls, then allocates a single mapping per thread that looks like so: - stack guard - stack [omitted for main thread and with pthread_attr_setstack] - static TLS: - bionic_tcb [exec TLS will either precede or succeed the TCB] - bionic_tls [prefixed by the pthread keys] - [solib TLS segments will be placed here] - guard page As before, if the new mapping includes a stack, the pthread_internal_t is allocated on it. At startup, Bionic allocates a temporary bionic_tcb object on the stack, then allocates a temporary bionic_tls object using mmap. This mmap is delayed because the linker can't currently call async_safe_fatal() before relocating itself. Later, Bionic allocates a stack-less thread mapping for the main thread, and copies slots from the temporary TCB to the new TCB. (See *::copy_from_bootstrap methods.) Bug: http://b/78026329 Test: bionic unit tests Test: verify that a Golang app still works Test: verify that a Golang app crashes if bionic_{tls,tcb} are swapped Merged-In: I6543063752f4ec8ef6dc9c7f2a06ce2a18fc5af3 Change-Id: I6543063752f4ec8ef6dc9c7f2a06ce2a18fc5af3 (cherry picked from commit 1e660b70da625fcbf1e43dfae09b7b4817fa1660)
2019-01-03 11:51:30 +01:00
/*
* Copyright (C) 2019 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#pragma once
#include <stdlib.h>
Implement arm64 TLSDESC 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
2019-01-24 02:47:10 +01:00
#include "private/bionic_elf_tls.h"
struct TlsModule;
struct soinfo;
void linker_setup_exe_static_tls(const char* progname);
void linker_finalize_static_tls();
void register_soinfo_tls(soinfo* si);
void unregister_soinfo_tls(soinfo* si);
const TlsModule& get_tls_module(size_t module_id);
Implement arm64 TLSDESC 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
2019-01-24 02:47:10 +01:00
typedef size_t TlsDescResolverFunc(size_t);
struct TlsDescriptor {
#if defined(__arm__)
size_t arg;
TlsDescResolverFunc* func;
#else
TlsDescResolverFunc* func;
size_t arg;
#endif
};
struct TlsDynamicResolverArg {
size_t generation;
TlsIndex index;
};
__LIBC_HIDDEN__ extern "C" size_t tlsdesc_resolver_static(size_t);
__LIBC_HIDDEN__ extern "C" size_t tlsdesc_resolver_dynamic(size_t);
__LIBC_HIDDEN__ extern "C" size_t tlsdesc_resolver_unresolved_weak(size_t);