History log of /src/libexec/ld.elf_so/README.TLS
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Revision tags: perseant-exfatfs-base-20250801 netbsd-11-base
# 1.7 22-Jul-2024 riastradh

ld.elf_so: Sprinkle comments and references for thread-local storage.

Maybe this will help the TLS business to be less mysterious to the
next traveller to pass by here.

Prompted by PR lib/58154.


Revision tags: perseant-exfatfs-base-20240630 perseant-exfatfs-base
# 1.6 04-Jun-2023 joerg

branches: 1.6.2;
Fix interactions of initial-exec TLS model and dlopen

(1) If an initial-exec relocation was used for a non-local symbol
(i.e. the definition of the symbol is in a different DSO), the
computation of the static TLS offset used the wrong DSO.
This would effectively mean the wrong address was computed
(PR toolchain/50277, PR pkg/57445).

Fix this by forcing the computation of the correct DSO (the one defining
the symbol).

This code uses __UNCONST to avoid the vast interface changes for this
special case.

(2) If symbols from a DSO loaded via dlopen are used with both
global-dynamic/local-dynamic and initial-exec relocations AND
a initial-exec relocation was resolved first in a thread, a split brain
situation could exist where the dynamic relocations would use one memory
block (separate allocation) and the initial-exec relocations the static
per-thread TLS space.

(3) If the initial-exec relocation in (2) is seen after any thread has
already used a GD/LD allocation, bail out. Since IE relocations are used
only in the GOT, this will prevent the dlopen. This is a bit more
aggressive than necessary, but a full blown reference counting doesn't
seem to be justified.


Revision tags: netbsd-10-base netbsd-9-3-RELEASE cjep_sun2x-base1 cjep_sun2x-base cjep_staticlib_x-base1 netbsd-9-2-RELEASE cjep_staticlib_x-base netbsd-9-1-RELEASE phil-wifi-20200421 phil-wifi-20200411 is-mlppp-base phil-wifi-20200406 netbsd-9-0-RELEASE netbsd-9-0-RC2 netbsd-9-0-RC1 phil-wifi-20191119 netbsd-9-base phil-wifi-20190609 pgoyette-compat-20190127 pgoyette-compat-20190118 pgoyette-compat-1226
# 1.5 01-Dec-2018 skrll

branches: 1.5.2; 1.5.10;
Fix typos


Revision tags: netbsd-8-3-RELEASE netbsd-8-2-RELEASE netbsd-8-1-RELEASE netbsd-8-1-RC1 pgoyette-compat-1126 pgoyette-compat-1020 pgoyette-compat-0930 pgoyette-compat-0906 netbsd-7-2-RELEASE pgoyette-compat-0728 netbsd-8-0-RELEASE phil-wifi-base pgoyette-compat-0625 netbsd-8-0-RC2 pgoyette-compat-0521 pgoyette-compat-0502 pgoyette-compat-0422 netbsd-8-0-RC1 pgoyette-compat-0415 pgoyette-compat-0407 pgoyette-compat-0330 pgoyette-compat-0322 pgoyette-compat-0315 netbsd-7-1-2-RELEASE pgoyette-compat-base netbsd-7-1-1-RELEASE matt-nb8-mediatek-base perseant-stdc-iso10646-base netbsd-8-base prg-localcount2-base3 prg-localcount2-base2 prg-localcount2-base1 prg-localcount2-base pgoyette-localcount-20170426 bouyer-socketcan-base1 pgoyette-localcount-20170320 netbsd-7-1-RELEASE netbsd-7-1-RC2 netbsd-7-nhusb-base-20170116 bouyer-socketcan-base pgoyette-localcount-20170107 netbsd-7-1-RC1 pgoyette-localcount-20161104 netbsd-7-0-2-RELEASE localcount-20160914 netbsd-7-nhusb-base pgoyette-localcount-20160806 pgoyette-localcount-20160726 pgoyette-localcount-base netbsd-7-0-1-RELEASE netbsd-7-0-RELEASE netbsd-7-0-RC3 netbsd-7-0-RC2 netbsd-7-0-RC1 netbsd-6-0-6-RELEASE netbsd-6-1-5-RELEASE netbsd-7-base yamt-pagecache-base9 yamt-pagecache-tag8 netbsd-6-1-4-RELEASE netbsd-6-0-5-RELEASE tls-earlyentropy-base riastradh-xf86-video-intel-2-7-1-pre-2-21-15 riastradh-drm2-base3 netbsd-6-1-3-RELEASE netbsd-6-0-4-RELEASE netbsd-6-1-2-RELEASE netbsd-6-0-3-RELEASE netbsd-6-1-1-RELEASE riastradh-drm2-base2 riastradh-drm2-base1 riastradh-drm2-base netbsd-6-0-2-RELEASE netbsd-6-1-RELEASE netbsd-6-1-RC4 netbsd-6-1-RC3 agc-symver-base netbsd-6-1-RC2 netbsd-6-1-RC1 yamt-pagecache-base8 netbsd-6-0-1-RELEASE yamt-pagecache-base7 matt-nb6-plus-nbase yamt-pagecache-base6 netbsd-6-0-RELEASE netbsd-6-0-RC2 tls-maxphys-base matt-nb6-plus-base netbsd-6-0-RC1 yamt-pagecache-base5 yamt-pagecache-base4 netbsd-6-base yamt-pagecache-base3 yamt-pagecache-base2 yamt-pagecache-base cherry-xenmp-base
# 1.4 10-Mar-2011 joerg

branches: 1.4.42; 1.4.44;
Add some clarifications


# 1.3 10-Mar-2011 joerg

Add source reference for _lwp_makecontext and
__HAVE___LWP_GETPRIVATE_FAST. Fix enumeration.


# 1.2 10-Mar-2011 joerg

Fix prototype for __tls_get_addr. Add a generic implementation of it
using __tls_get_addr. Update TLS notes.


# 1.1 09-Mar-2011 joerg

Add TLS support infrastructure. For dynamic binaries, ld.elf_so exports
_rtld_tls_allocate and _rtld_tls_free. libpthread uses this functions to
setup the thread private area of all new threads. ld.elf_so is
responsible for setting up the private area for the initial thread.
Similar functions are called from _libc_init for static binaries, using
dl_iterate_phdr to access the ELF Program Header.

Add test cases to exercise the different TLS storage models. Test cases
are compiled and installed on all platforms, but are skipped on
platforms not marked for TLS support.

This material is based upon work partially supported by
The NetBSD Foundation under a contract with Joerg Sonnenberger.

It is inspired by the TLS support in FreeBSD by Doug Rabson and the
clean ups of the DragonFly port of the original FreeBSD modifications.