From 34e0882b83aedc6fb9c7532c89afaf8e0043b7ce Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Tue, 29 Aug 2017 15:55:33 +0930 Subject: [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. --- elfcpp/ChangeLog | 5 +++++ elfcpp/elfcpp.h | 3 +++ elfcpp/powerpc.h | 6 ++++++ 3 files changed, 14 insertions(+) (limited to 'elfcpp') diff --git a/elfcpp/ChangeLog b/elfcpp/ChangeLog index f6692486268..200d0d4ee47 100644 --- a/elfcpp/ChangeLog +++ b/elfcpp/ChangeLog @@ -1,3 +1,8 @@ +2017-08-29 Alan Modra + + * elfcpp.h (DT_PPC_OPT): Define. + * powerpc.h (PPC_OPT_TLS): Define. + 2017-07-28 H.J. Lu PR gold/21857 diff --git a/elfcpp/elfcpp.h b/elfcpp/elfcpp.h index cccec4c2560..1f629ced05d 100644 --- a/elfcpp/elfcpp.h +++ b/elfcpp/elfcpp.h @@ -768,6 +768,9 @@ enum DT // Specify the value of _GLOBAL_OFFSET_TABLE_. DT_PPC_GOT = 0x70000000, + // Specify whether various optimisations are possible. + DT_PPC_OPT = 0x70000001, + // Specify the start of the .glink section. DT_PPC64_GLINK = 0x70000000, diff --git a/elfcpp/powerpc.h b/elfcpp/powerpc.h index 3dc08286777..71cac5e4105 100644 --- a/elfcpp/powerpc.h +++ b/elfcpp/powerpc.h @@ -228,6 +228,12 @@ enum EF_PPC64_ABI = 3 }; +// DT_PPC_OPT bits +enum +{ + PPC_OPT_TLS = 1 +}; + // DT_PPC64_OPT bits enum { -- cgit v1.2.1