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[GOLD] PowerPC tls_get_addr_optimize
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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Lines changed: 454 additions & 57 deletions

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‎elfcpp/ChangeLog‎

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2017-08-29 Alan Modra <amodra@gmail.com>
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* elfcpp.h (DT_PPC_OPT): Define.
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* powerpc.h (PPC_OPT_TLS): Define.
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2017-07-28 H.J. Lu <hongjiu.lu@intel.com>
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PR gold/21857

‎elfcpp/elfcpp.h‎

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// Specify the value of _GLOBAL_OFFSET_TABLE_.
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DT_PPC_GOT = 0x70000000,
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// Specify whether various optimisations are possible.
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DT_PPC_OPT = 0x70000001,
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// Specify the start of the .glink section.
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DT_PPC64_GLINK = 0x70000000,
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‎elfcpp/powerpc.h‎

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EF_PPC64_ABI = 3
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};
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// DT_PPC_OPT bits
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enum
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{
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PPC_OPT_TLS = 1
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};
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// DT_PPC64_OPT bits
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enum
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{

‎gold/ChangeLog‎

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2017-08-29 Alan Modra <amodra@gmail.com>
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* options.h (tls_get_addr_optimize): New option.
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* symtab.h (Symbol::clear_in_reg, clone): New functions.
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(Sized_symbol::clone): New function.
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(Symbol_table::clone): New function.
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* resolve.cc (Symbol::clone, Sized_symbol::clone): New functions.
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* powerpc.cc (Target_powerpc::has_tls_get_addr_opt_,
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tls_get_addr_, tls_get_addr_opt_): New vars.
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(Target_powerpc::tls_get_addr_opt, tls_get_addr,
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is_tls_get_addr_opt, replace_tls_get_addr,
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set_has_tls_get_addr_opt, stk_linker): New functions.
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(Target_powerpc::Track_tls::maybe_skip_tls_get_addr_call): Add
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target param. Update callers. Compare symbols rather than names.
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(Target_powerpc::do_define_standard_symbols): Init tls_get_addr_
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and tls_get_addr_opt_.
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(Target_powerpc::Branch_info::mark_pltcall): Translate tls_get_addr
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sym to tls_get_addr_opt.
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(Target_powerpc::Branch_info::make_stub): Likewise.
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(Stub_table::define_stub_syms): Likewise.
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(Target_powerpc::Scan::global): Likewise.
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(Target_powerpc::Relocate::relocate): Likewise.
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(add_3_12_2, add_3_12_13, bctrl, beqlr, cmpdi_11_0, cmpwi_11_0,
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ld_11_1, ld_11_3, ld_12_3, lwz_11_3, lwz_12_3, mr_0_3, mr_3_0,
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mtlr_11, std_11_1): New constants.
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(Stub_table::eh_frame_added_): Delete.
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(Stub_table::tls_get_addr_opt_bctrl_, plt_fde_len_, plt_fde_): New vars.
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(Stub_table::init_plt_fde): New functions.
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(Stub_table::add_eh_frame, replace_eh_frame): Move definition out
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of line. Init and use plt_fde_.
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(Stub_table::plt_call_size): Return size for tls_get_addr stub.
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Extract alignment code to..
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(Stub_table::plt_call_align): ..this new function. Adjust all callers.
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(Stub_table::add_plt_call_entry): Set has_tls_get_addr_opt and
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tls_get_addr_opt_bctrl, and align after that.
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(Stub_table::do_write): Write out tls_get_addr stub.
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(Target_powerpc::do_finalize_sections): Emit DT_PPC_OPT
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PPC_OPT_TLS/PPC64_OPT_TLS bit.
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(Target_powerpc::Relocate::relocate): Don't check for or modify
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nop following bl for tls_get_addr stub.
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2017-08-29 Alan Modra <amodra@gmail.com>
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* symtab.h (Symbol): Split u_ into u1_ and u2_. Adjust accessors

‎gold/options.h‎

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DEFINE_bool(tls_optimize, options::TWO_DASHES, '\0', true,
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N_("(PowerPC/64 only) Optimize GD/LD/IE code to IE/LE"),
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N_("(PowerPC/64 only) Don'\''t try to optimize TLS accesses"));
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DEFINE_bool(tls_get_addr_optimize, options::TWO_DASHES, '\0', true,
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N_("(PowerPC/64 only) Use a special __tls_get_addr call"),
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N_("(PowerPC/64 only) Don't use a special __tls_get_addr call"));
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DEFINE_bool(toc_optimize, options::TWO_DASHES, '\0', true,
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N_("(PowerPC64 only) Optimize TOC code sequences"),

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