| /* |
| * 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. |
| */ |
| |
| #include "private/bionic_elf_tls.h" |
| |
| #include <async_safe/log.h> |
| #include <sys/param.h> |
| #include <unistd.h> |
| |
| #include "private/bionic_macros.h" |
| #include "private/bionic_tls.h" |
| |
| // Search for a TLS segment in the given phdr table. Returns true if it has a |
| // TLS segment and false otherwise. |
| bool __bionic_get_tls_segment(const ElfW(Phdr)* phdr_table, size_t phdr_count, |
| ElfW(Addr) load_bias, const char* mod_name, |
| TlsSegment* out) { |
| for (size_t i = 0; i < phdr_count; ++i) { |
| const ElfW(Phdr)& phdr = phdr_table[i]; |
| if (phdr.p_type == PT_TLS) { |
| // N.B. The size does not need to be a multiple of the alignment. With |
| // ld.bfd (or after using binutils' strip), the TLS segment's size isn't |
| // rounded up. |
| size_t alignment = phdr.p_align; |
| if (alignment == 0 || !powerof2(alignment)) { |
| async_safe_fatal("error: \"%s\": TLS segment alignment is not a power of 2: %zu", |
| mod_name, alignment); |
| } |
| // Bionic only respects TLS alignment up to one page. |
| alignment = MIN(alignment, PAGE_SIZE); |
| *out = TlsSegment { |
| phdr.p_memsz, |
| alignment, |
| reinterpret_cast<void*>(load_bias + phdr.p_vaddr), |
| phdr.p_filesz, |
| }; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| // Reserves space for the Bionic TCB and the executable's TLS segment. Returns |
| // the offset of the executable's TLS segment. |
| size_t StaticTlsLayout::reserve_exe_segment_and_tcb(const TlsSegment* exe_segment, |
| const char* progname __attribute__((unused))) { |
| // Special case: if the executable has no TLS segment, then just allocate a |
| // TCB and skip the minimum alignment check on ARM. |
| if (exe_segment == nullptr) { |
| offset_bionic_tcb_ = reserve_type<bionic_tcb>(); |
| return 0; |
| } |
| |
| #if defined(__arm__) || defined(__aarch64__) |
| |
| // First reserve enough space for the TCB before the executable segment. |
| reserve(sizeof(bionic_tcb), 1); |
| |
| // Then reserve the segment itself. |
| const size_t result = reserve(exe_segment->size, exe_segment->alignment); |
| |
| // The variant 1 ABI that ARM linkers follow specifies a 2-word TCB between |
| // the thread pointer and the start of the executable's TLS segment, but both |
| // the thread pointer and the TLS segment are aligned appropriately for the |
| // TLS segment. Calculate the distance between the thread pointer and the |
| // EXE's segment. |
| const size_t exe_tpoff = __BIONIC_ALIGN(sizeof(void*) * 2, exe_segment->alignment); |
| |
| const size_t min_bionic_alignment = BIONIC_ROUND_UP_POWER_OF_2(MAX_TLS_SLOT) * sizeof(void*); |
| if (exe_tpoff < min_bionic_alignment) { |
| async_safe_fatal("error: \"%s\": executable's TLS segment is underaligned: " |
| "alignment is %zu, needs to be at least %zu for %s Bionic", |
| progname, exe_segment->alignment, min_bionic_alignment, |
| (sizeof(void*) == 4 ? "ARM" : "ARM64")); |
| } |
| |
| offset_bionic_tcb_ = result - exe_tpoff - (-MIN_TLS_SLOT * sizeof(void*)); |
| return result; |
| |
| #elif defined(__i386__) || defined(__x86_64__) |
| |
| // x86 uses variant 2 TLS layout. The executable's segment is located just |
| // before the TCB. |
| static_assert(MIN_TLS_SLOT == 0, "First slot of bionic_tcb must be slot #0 on x86"); |
| const size_t exe_size = round_up_with_overflow_check(exe_segment->size, exe_segment->alignment); |
| reserve(exe_size, 1); |
| const size_t max_align = MAX(alignof(bionic_tcb), exe_segment->alignment); |
| offset_bionic_tcb_ = reserve(sizeof(bionic_tcb), max_align); |
| return offset_bionic_tcb_ - exe_size; |
| |
| #else |
| #error "Unrecognized architecture" |
| #endif |
| } |
| |
| void StaticTlsLayout::reserve_bionic_tls() { |
| offset_bionic_tls_ = reserve_type<bionic_tls>(); |
| } |
| |
| void StaticTlsLayout::finish_layout() { |
| // Round the offset up to the alignment. |
| offset_ = round_up_with_overflow_check(offset_, alignment_); |
| |
| if (overflowed_) { |
| async_safe_fatal("error: TLS segments in static TLS overflowed"); |
| } |
| } |
| |
| // The size is not required to be a multiple of the alignment. The alignment |
| // must be a positive power-of-two. |
| size_t StaticTlsLayout::reserve(size_t size, size_t alignment) { |
| offset_ = round_up_with_overflow_check(offset_, alignment); |
| const size_t result = offset_; |
| if (__builtin_add_overflow(offset_, size, &offset_)) overflowed_ = true; |
| alignment_ = MAX(alignment_, alignment); |
| return result; |
| } |
| |
| size_t StaticTlsLayout::round_up_with_overflow_check(size_t value, size_t alignment) { |
| const size_t old_value = value; |
| value = __BIONIC_ALIGN(value, alignment); |
| if (value < old_value) overflowed_ = true; |
| return value; |
| } |