2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2004 Doug Rabson
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * Define stubs for TLS internals so that programs and libraries can
33 * link. These functions will be replaced by functional versions at
34 * runtime from ld-elf.so.1.
37 #include <sys/cdefs.h>
38 #include <sys/param.h>
45 #include "libc_private.h"
47 #define tls_assert(cond) ((cond) ? (void) 0 : \
48 (tls_msg(#cond ": assert failed: " __FILE__ ":" \
49 __XSTRING(__LINE__) "\n"), abort()))
50 #define tls_msg(s) write(STDOUT_FILENO, s, strlen(s))
52 /* Provided by jemalloc to avoid bootstrapping issues. */
53 void *__je_bootstrap_malloc(size_t size);
54 void *__je_bootstrap_calloc(size_t num, size_t size);
55 void __je_bootstrap_free(void *ptr);
57 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
58 __weak_reference(__libc_free_tls, _rtld_free_tls);
62 __weak_reference(___libc_tls_get_addr, ___tls_get_addr);
63 __attribute__((__regparm__(1))) void * ___libc_tls_get_addr(void *);
67 void * __libc_tls_get_addr(void *);
68 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
70 void *_rtld_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign);
71 void _rtld_free_tls(void *tls, size_t tcbsize, size_t tcbalign);
72 void *__libc_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign);
73 void __libc_free_tls(void *tls, size_t tcbsize, size_t tcbalign);
77 static size_t libc_tls_static_space;
78 static size_t libc_tls_init_size;
79 static size_t libc_tls_init_align;
80 static void *libc_tls_init;
84 __libc_tls_get_addr(void *vti)
89 dtv = _tcb_get()->tcb_dtv;
91 return ((char *)(dtv[ti->ti_module + 1] + ti->ti_offset) +
99 __attribute__((__regparm__(1)))
101 ___libc_tls_get_addr(void *vti)
103 return (__libc_tls_get_addr(vti));
111 libc_malloc_aligned(size_t size, size_t align)
115 if (align < sizeof(void *))
116 align = sizeof(void *);
118 mem = __je_bootstrap_malloc(size + sizeof(void *) + align - 1);
119 res = (void *)roundup2((uintptr_t)mem + sizeof(void *), align);
120 *(void **)((uintptr_t)res - sizeof(void *)) = mem;
125 libc_free_aligned(void *ptr)
136 __je_bootstrap_free(mem);
142 * There are two versions of variant I of TLS
144 * - ARM and aarch64 uses original variant I as is described in [1] and [2],
145 * where TP points to start of TCB followed by aligned TLS segment.
146 * Both TCB and TLS must be aligned to alignment of TLS section. The TCB[0]
147 * points to DTV vector and DTV values are real addresses (without bias).
148 * Note: for Local Exec TLS Model, the offsets from TP (TCB in this case) to
149 * TLS variables are computed by linker, so we cannot overalign TLS section.
151 * - PowerPC and RISC-V use modified version of variant I, described in [3]
152 * where TP points (with bias) to TLS and TCB immediately precedes TLS without
153 * any alignment gap[4]. Only TLS should be aligned. The TCB[0] points to DTV
154 * vector and DTV values are biased by constant value (TLS_DTV_OFFSET) from
157 * [1] Ulrich Drepper: ELF Handling for Thread-Local Storage
158 * www.akkadia.org/drepper/tls.pdf
160 * [2] ARM IHI 0045E: Addenda to, and Errata in, the ABI for the ARM(r)
162 * infocenter.arm.com/help/topic/com.arm.doc.ihi0045e/IHI0045E_ABI_addenda.pdf
164 * [3] OpenPOWER: Power Architecture 64-Bit ELF V2 ABI Specification
165 * https://members.openpowerfoundation.org/document/dl/576
167 * [4] Its unclear if "without any alignment gap" is hard ABI requirement,
168 * but we must follow this rule due to suboptimal _tcb_set()
169 * (aka <ARCH>_SET_TP) implementation. This function doesn't expect TP but
172 * [5] I'm not able to validate "values are biased" assertions.
176 * Return pointer to allocated TLS block
179 get_tls_block_ptr(void *tcb, size_t tcbsize)
181 size_t extra_size, post_size, pre_size, tls_block_size;
183 /* Compute fragments sizes. */
184 extra_size = tcbsize - TLS_TCB_SIZE;
185 #if defined(__aarch64__) || defined(__arm__)
186 post_size = roundup2(TLS_TCB_SIZE, libc_tls_init_align) - TLS_TCB_SIZE;
190 tls_block_size = tcbsize + post_size;
191 pre_size = roundup2(tls_block_size, libc_tls_init_align) -
194 return ((char *)tcb - pre_size - extra_size);
198 * Free Static TLS using the Variant I method. The tcbsize
199 * and tcbalign parameters must be the same as those used to allocate
203 __libc_free_tls(void *tcb, size_t tcbsize, size_t tcbalign __unused)
208 tls = (Elf_Addr **)tcb;
210 __je_bootstrap_free(dtv);
211 libc_free_aligned(get_tls_block_ptr(tcb, tcbsize));
215 * Allocate Static TLS using the Variant I method.
217 * To handle all above requirements, we setup the following layout for
219 * (whole memory block is aligned with MAX(TLS_TCB_ALIGN, tls_init_align))
221 * +----------+--------------+--------------+-----------+------------------+
222 * | pre gap | extended TCB | TCB | post gap | TLS segment |
223 * | pre_size | extra_size | TLS_TCB_SIZE | post_size | tls_static_space |
224 * +----------+--------------+--------------+-----------+------------------+
227 * extra_size is tcbsize - TLS_TCB_SIZE
228 * post_size is used to adjust TCB to TLS alignment for first version of TLS
229 * layout and is always 0 for second version.
230 * pre_size is used to adjust TCB alignment for first version and to adjust
231 * TLS alignment for second version.
235 __libc_allocate_tls(void *oldtcb, size_t tcbsize, size_t tcbalign)
237 Elf_Addr *dtv, **tcb;
238 char *tls_block, *tls;
239 size_t extra_size, maxalign, post_size, pre_size, tls_block_size;
241 if (oldtcb != NULL && tcbsize == TLS_TCB_SIZE)
244 tls_assert(tcbalign >= TLS_TCB_ALIGN);
245 maxalign = MAX(tcbalign, libc_tls_init_align);
247 /* Compute fragmets sizes. */
248 extra_size = tcbsize - TLS_TCB_SIZE;
249 #if defined(__aarch64__) || defined(__arm__)
250 post_size = roundup2(TLS_TCB_SIZE, libc_tls_init_align) - TLS_TCB_SIZE;
254 tls_block_size = tcbsize + post_size;
255 pre_size = roundup2(tls_block_size, libc_tls_init_align) -
257 tls_block_size += pre_size + libc_tls_static_space;
259 /* Allocate whole TLS block */
260 tls_block = libc_malloc_aligned(tls_block_size, maxalign);
261 if (tls_block == NULL) {
262 tls_msg("__libc_allocate_tls: Out of memory.\n");
265 memset(tls_block, 0, tls_block_size);
266 tcb = (Elf_Addr **)(tls_block + pre_size + extra_size);
267 tls = (char *)tcb + TLS_TCB_SIZE + post_size;
269 if (oldtcb != NULL) {
270 memcpy(tls_block, get_tls_block_ptr(oldtcb, tcbsize),
272 libc_free_aligned(oldtcb);
274 /* Adjust the DTV. */
276 dtv[2] = (Elf_Addr)(tls + TLS_DTV_OFFSET);
278 dtv = __je_bootstrap_malloc(3 * sizeof(Elf_Addr));
280 tls_msg("__libc_allocate_tls: Out of memory.\n");
285 dtv[0] = 1; /* Generation. */
286 dtv[1] = 1; /* Segments count. */
287 dtv[2] = (Elf_Addr)(tls + TLS_DTV_OFFSET);
289 if (libc_tls_init_size > 0)
290 memcpy(tls, libc_tls_init, libc_tls_init_size);
298 #ifdef TLS_VARIANT_II
301 * Free Static TLS using the Variant II method.
304 __libc_free_tls(void *tcb, size_t tcbsize __unused, size_t tcbalign)
308 Elf_Addr tlsstart, tlsend;
311 * Figure out the size of the initial TLS block so that we can
312 * find stuff which ___tls_get_addr() allocated dynamically.
314 tcbalign = MAX(tcbalign, libc_tls_init_align);
315 size = roundup2(libc_tls_static_space, tcbalign);
317 dtv = ((Elf_Addr**)tcb)[1];
318 tlsend = (Elf_Addr) tcb;
319 tlsstart = tlsend - size;
320 libc_free_aligned((void*)tlsstart);
321 __je_bootstrap_free(dtv);
325 * Allocate Static TLS using the Variant II method.
328 __libc_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign)
333 Elf_Addr segbase, oldsegbase;
335 tcbalign = MAX(tcbalign, libc_tls_init_align);
336 size = roundup2(libc_tls_static_space, tcbalign);
338 if (tcbsize < 2 * sizeof(Elf_Addr))
339 tcbsize = 2 * sizeof(Elf_Addr);
340 tls = libc_malloc_aligned(size + tcbsize, tcbalign);
342 tls_msg("__libc_allocate_tls: Out of memory.\n");
345 memset(tls, 0, size + tcbsize);
346 dtv = __je_bootstrap_malloc(3 * sizeof(Elf_Addr));
348 tls_msg("__libc_allocate_tls: Out of memory.\n");
352 segbase = (Elf_Addr)(tls + size);
353 ((Elf_Addr*)segbase)[0] = segbase;
354 ((Elf_Addr*)segbase)[1] = (Elf_Addr) dtv;
358 dtv[2] = segbase - libc_tls_static_space;
362 * Copy the static TLS block over whole.
364 oldsegbase = (Elf_Addr) oldtls;
365 memcpy((void *)(segbase - libc_tls_static_space),
366 (const void *)(oldsegbase - libc_tls_static_space),
367 libc_tls_static_space);
370 * We assume that this block was the one we created with
371 * allocate_initial_tls().
373 _rtld_free_tls(oldtls, 2*sizeof(Elf_Addr), sizeof(Elf_Addr));
375 memcpy((void *)(segbase - libc_tls_static_space),
376 libc_tls_init, libc_tls_init_size);
377 memset((void *)(segbase - libc_tls_static_space +
378 libc_tls_init_size), 0,
379 libc_tls_static_space - libc_tls_init_size);
382 return (void*) segbase;
385 #endif /* TLS_VARIANT_II */
390 __libc_allocate_tls(void *oldtls __unused, size_t tcbsize __unused,
391 size_t tcbalign __unused)
397 __libc_free_tls(void *tcb __unused, size_t tcbsize __unused,
398 size_t tcbalign __unused)
404 extern char **environ;
411 Elf_Auxinfo *aux, *auxp;
417 sp = (Elf_Addr *) environ;
420 aux = (Elf_Auxinfo *) sp;
423 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
424 switch (auxp->a_type) {
426 phdr = auxp->a_un.a_ptr;
430 phent = auxp->a_un.a_val;
434 phnum = auxp->a_un.a_val;
438 if (phdr == NULL || phent != sizeof(Elf_Phdr) || phnum == 0)
441 for (i = 0; (unsigned) i < phnum; i++) {
442 if (phdr[i].p_type == PT_TLS) {
443 libc_tls_static_space = roundup2(phdr[i].p_memsz,
445 libc_tls_init_size = phdr[i].p_filesz;
446 libc_tls_init_align = phdr[i].p_align;
447 libc_tls_init = (void *)phdr[i].p_vaddr;
451 tls = _rtld_allocate_tls(NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN);