Fix prototype for __tls_get_addr. Add a generic implementation of it
using __tls_get_addr. Update TLS notes.
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joerg
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9eacb1b321
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de4cf97515
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@ -3,11 +3,7 @@ Steps for adding TLS support for a new platform:
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(1) Declare TLS variant in machine/types.h by defining either
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__HAVE_TLS_VARIANT_I or __HAVE_TLS_VARIANT_II.
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(2) crt0.o has to call _rtld_tls_static_setup() if _DYNAMIC == NULL.
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This part is already done if the new src/lib/csu/arch layout is used
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by the architecture.
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(3) _lwp_makecontext has to set the reserved register or kernel transfer
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(2) _lwp_makecontext has to set the reserved register or kernel transfer
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variable in uc_mcontext to the provided value of 'private'.
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This is not possible on the VAX as there is no free space in ucontext_t.
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@ -15,38 +11,21 @@ This requires either a special version of _lwp_create or versioning
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everything using ucontext_t. Debug support depends on getting the data from
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ucontext_t, so the second option is possibly required.
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(4) _lwp_setprivate(2) has to update the same register as
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(3) _lwp_setprivate(2) has to update the same register as
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_lwp_makecontext. cpu_lwp_setprivate has to call _lwp_setprivate(2) to
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reflect the kernel view. cpu_switch has to update the mapping.
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_lwp_setprivate is used for the initial thread, all other threads
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created by libpthread use _lwp_makecontext for this purpose.
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(5) Provide __tls_get_addr and possible other MD functions for dynamic
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(4) Provide __tls_get_addr and possible other MD functions for dynamic
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TLS offset computation. If such alternative entry points exist (currently
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only i386), also add a weak reference to 0 in src/lib/libc/tls/tls.c.
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The generic implementation is:
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The generic implementation can be found in tls.c and is used with
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__HAVE_COMMON___TLS_GET_ADDR. It depends on ___lwp_getprivate_fast.
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#include <sys/cdefs.h>
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#include <sys/tls.h>
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#include <lwp.h>
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/* Weak entry is overriden by ld.elf_so for dynamic linkage */
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weak_alias(__tls_get_addr, __libc__tls_get_addr)
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void *
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__libc__tls_get_addr(size_t idx[2])
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{
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struct tls_tcb *tcb;
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tcb = _lwp_getprivate();
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return _rtld_tls_get_addr(tcb, idx[0], idx[1]);
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}
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XXX Document optimisations based idx[0]
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(6) Implement the necessary relocation records in mdreloc.c. There are
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(5) Implement the necessary relocation records in mdreloc.c. There are
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typically three relocation types found in dynamic binaries:
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(a) R_TYPE(TLS_DTPOFF): Offset inside the module. The common TLS code
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@ -73,7 +52,7 @@ def->st_value - defobj->tlsoffset + rela->r_addend
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e.g. starting offset is counting down from the TCB.
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(7) Implement _lwp_getprivate_fast() in machine/mcontext.h and set
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(6) Implement _lwp_getprivate_fast() in machine/mcontext.h and set
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__HAVE___LWP_GETPRIVATE_FAST.
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(8) Test using src/tests/lib/libc/tls. Make sure with "objdump -R" that
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@ -1,4 +1,4 @@
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/* $NetBSD: rtld.h,v 1.101 2011/03/09 23:10:07 joerg Exp $ */
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/* $NetBSD: rtld.h,v 1.102 2011/03/10 14:27:31 joerg Exp $ */
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/*
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* Copyright 1996 John D. Polstra.
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@ -374,7 +374,7 @@ void _rtld_tls_offset_free(Obj_Entry *);
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extern size_t _rtld_tls_dtv_generation;
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extern size_t _rtld_tls_max_index;
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__dso_public extern void __tls_get_addr(void *);
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__dso_public extern void *__tls_get_addr(void *);
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#endif
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/* map_object.c */
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@ -1,4 +1,4 @@
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/* $NetBSD: tls.c,v 1.1 2011/03/09 23:10:07 joerg Exp $ */
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/* $NetBSD: tls.c,v 1.2 2011/03/10 14:27:31 joerg Exp $ */
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/*-
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* Copyright (c) 2011 The NetBSD Foundation, Inc.
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* All rights reserved.
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@ -29,9 +29,10 @@
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: tls.c,v 1.1 2011/03/09 23:10:07 joerg Exp $");
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__RCSID("$NetBSD: tls.c,v 1.2 2011/03/10 14:27:31 joerg Exp $");
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#include <sys/param.h>
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#include <sys/ucontext.h>
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#include <lwp.h>
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#include <string.h>
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#include "rtld.h"
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@ -232,4 +233,28 @@ _rtld_tls_offset_free(Obj_Entry *obj)
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return;
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}
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#ifdef __HAVE_COMMON___TLS_GET_ADDR
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/*
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* The fast path is access to an already allocated DTV entry.
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* This checks the current limit and the entry without needing any
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* locking. Entries are only freed on dlclose() and it is an application
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* bug if code of the module is still running at that point.
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*/
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void *
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__tls_get_addr(void *arg_)
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{
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size_t *arg = (size_t *)arg_;
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void **dtv;
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struct tls_tcb *tcb = __lwp_getprivate_fast();
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size_t idx = arg[0], offset = arg[1];
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dtv = tcb->tcb_dtv;
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if (__predict_true(idx < DTV_MAX_INDEX(dtv) && dtv[idx] != NULL))
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return (uint8_t *)dtv[idx] + offset;
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return _rtld_tls_get_addr(tcb, idx, offset);
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}
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#endif
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#endif /* __HAVE_TLS_VARIANT_I || __HAVE_TLS_VARIANT_II */
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