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This implements the special __tls_get_addr_opt call stub for powerpc gold that returns __thread variable addresses without actually making a call to __tls_get_addr in most cases. Shared libraries that are loaded at program load time (ie. dlopen is not used) have a known layout for their __thread variables, and thus DTPMOD64/DPTREL64 pairs describing those variables can be set up by ld.so for the __tls_get_addr_opt call stub fast exit. Ref https://sourceware.org/ml/libc-alpha/2015-03/msg00626.html I really, really wish I'd used a differently versioned __tls_get_addr symbol than the base symbol to indicate glibc support for the optimized call, rather than having glibc export __tls_get_addr_opt. A lot of the messing around here, flipping symbols from __tls_get_addr to __tls_get_addr_opt, is caused by that decision. About the only benefit is that a user can see at a glance that their disassembled code is calling __tls_get_addr via the fancy call stub.. Anyway, we need references to __tls_get_addr to seem like they were to __tls_get_addr_opt, and in cases like the tsan interceptor, a definition of __tls_get_addr to seem like one of __tls_get_addr_opt as well. That's the reason for Symbol::clear_in_reg and Symbol_table::clone, and why symbols are substituted in Scan::global and other places dealing with dynamic linking. elfcpp/ * elfcpp.h (DT_PPC_OPT): Define. * powerpc.h (PPC_OPT_TLS): Define. gold/ * options.h (tls_get_addr_optimize): New option. * symtab.h (Symbol::clear_in_reg, clone): New functions. (Sized_symbol::clone): New function. (Symbol_table::clone): New function. * resolve.cc (Symbol::clone, Sized_symbol::clone): New functions. * powerpc.cc (Target_powerpc::has_tls_get_addr_opt_, tls_get_addr_, tls_get_addr_opt_): New vars. (Target_powerpc::tls_get_addr_opt, tls_get_addr, is_tls_get_addr_opt, replace_tls_get_addr, set_has_tls_get_addr_opt, stk_linker): New functions. (Target_powerpc::Track_tls::maybe_skip_tls_get_addr_call): Add target param. Update callers. Compare symbols rather than names. (Target_powerpc::do_define_standard_symbols): Init tls_get_addr_ and tls_get_addr_opt_. (Target_powerpc::Branch_info::mark_pltcall): Translate tls_get_addr sym to tls_get_addr_opt. (Target_powerpc::Branch_info::make_stub): Likewise. (Stub_table::define_stub_syms): Likewise. (Target_powerpc::Scan::global): Likewise. (Target_powerpc::Relocate::relocate): Likewise. (add_3_12_2, add_3_12_13, bctrl, beqlr, cmpdi_11_0, cmpwi_11_0, ld_11_1, ld_11_3, ld_12_3, lwz_11_3, lwz_12_3, mr_0_3, mr_3_0, mtlr_11, std_11_1): New constants. (Stub_table::eh_frame_added_): Delete. (Stub_table::tls_get_addr_opt_bctrl_, plt_fde_len_, plt_fde_): New vars. (Stub_table::init_plt_fde): New functions. (Stub_table::add_eh_frame, replace_eh_frame): Move definition out of line. Init and use plt_fde_. (Stub_table::plt_call_size): Return size for tls_get_addr stub. Extract alignment code to.. (Stub_table::plt_call_align): ..this new function. Adjust all callers. (Stub_table::add_plt_call_entry): Set has_tls_get_addr_opt and tls_get_addr_opt_bctrl, and align after that. (Stub_table::do_write): Write out tls_get_addr stub. (Target_powerpc::do_finalize_sections): Emit DT_PPC_OPT PPC_OPT_TLS/PPC64_OPT_TLS bit. (Target_powerpc::Relocate::relocate): Don't check for or modify nop following bl for tls_get_addr stub. |
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| .. | ||
| aarch64.h | ||
| arm.h | ||
| ChangeLog | ||
| ChangeLog-0815 | ||
| ChangeLog-2016 | ||
| dwarf.h | ||
| elfcpp_file.h | ||
| elfcpp_internal.h | ||
| elfcpp_swap.h | ||
| elfcpp.h | ||
| i386.h | ||
| mips.h | ||
| powerpc.h | ||
| README | ||
| s390.h | ||
| sparc.h | ||
| tilegx.h | ||
| x86_64.h | ||
elfcpp is a C++ library for reading and writing ELF information. This
was written to support gold, the ELF linker, and may not be generally
useful.
elfcpp does not do file I/O. It deals only with offsets and memory
data.
For efficiency, most accessors are templates with two arguments: the
ELF file class (32 or 64 bits) and the endianness.
Copyright (C) 2012-2017 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.