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>
44 #include "libc_private.h"
46 #define tls_assert(cond) ((cond) ? (void) 0 : \
47 (tls_msg(#cond ": assert failed: " __FILE__ ":" \
48 __XSTRING(__LINE__) "\n"), abort()))
49 #define tls_msg(s) write(STDOUT_FILENO, s, strlen(s))
51 /* Provided by jemalloc to avoid bootstrapping issues. */
52 void *__je_bootstrap_malloc(size_t size);
53 void *__je_bootstrap_calloc(size_t num, size_t size);
54 void __je_bootstrap_free(void *ptr);
56 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
57 __weak_reference(__libc_free_tls, _rtld_free_tls);
61 __weak_reference(___libc_tls_get_addr, ___tls_get_addr);
62 __attribute__((__regparm__(1))) void * ___libc_tls_get_addr(void *);
66 void * __libc_tls_get_addr(void *);
67 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
69 void *_rtld_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign);
70 void _rtld_free_tls(void *tls, size_t tcbsize, size_t tcbalign);
71 void *__libc_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign);
72 void __libc_free_tls(void *tls, size_t tcbsize, size_t tcbalign);
74 #if defined(__amd64__)
75 #define TLS_TCB_ALIGN 16
76 #elif defined(__aarch64__) || defined(__arm__) || defined(__i386__) || \
77 defined(__mips__) || defined(__powerpc__) || defined(__riscv)
78 #define TLS_TCB_ALIGN sizeof(void *)
80 #error TLS_TCB_ALIGN undefined for target architecture
83 #if defined(__aarch64__) || defined(__arm__) || defined(__mips__) || \
84 defined(__powerpc__) || defined(__riscv)
87 #if defined(__i386__) || defined(__amd64__)
88 #define TLS_VARIANT_II
91 #if defined(__mips__) || defined(__powerpc__) || defined(__riscv)
92 #define DTV_OFFSET 0x8000
99 static size_t tls_static_space;
100 static size_t tls_init_size;
101 static size_t tls_init_align;
102 static void *tls_init;
109 __attribute__((__regparm__(1)))
111 ___libc_tls_get_addr(void *ti __unused)
119 __libc_tls_get_addr(void *ti __unused)
127 malloc_aligned(size_t size, size_t align)
131 if (align < sizeof(void *))
132 align = sizeof(void *);
134 mem = __je_bootstrap_malloc(size + sizeof(void *) + align - 1);
135 res = (void *)roundup2((uintptr_t)mem + sizeof(void *), align);
136 *(void **)((uintptr_t)res - sizeof(void *)) = mem;
141 free_aligned(void *ptr)
152 __je_bootstrap_free(mem);
158 * There are two versions of variant I of TLS
160 * - ARM and aarch64 uses original variant I as is described in [1] and [2],
161 * where TP points to start of TCB followed by aligned TLS segment.
162 * Both TCB and TLS must be aligned to alignment of TLS section. The TCB[0]
163 * points to DTV vector and DTV values are real addresses (without bias).
164 * Note: for Local Exec TLS Model, the offsets from TP (TCB in this case) to
165 * TLS variables are computed by linker, so we cannot overalign TLS section.
167 * - MIPS, PowerPC and RISC-V use modified version of variant I,
168 * described in [3] where TP points (with bias) to TLS and TCB immediately
169 * precedes TLS without any alignment gap[4]. Only TLS should be aligned.
170 * The TCB[0] points to DTV vector and DTV values are biased by constant
171 * value (0x8000) from real addresses[5].
173 * [1] Ulrich Drepper: ELF Handling for Thread-Local Storage
174 * www.akkadia.org/drepper/tls.pdf
176 * [2] ARM IHI 0045E: Addenda to, and Errata in, the ABI for the ARM(r)
178 * infocenter.arm.com/help/topic/com.arm.doc.ihi0045e/IHI0045E_ABI_addenda.pdf
180 * [3] OpenPOWER: Power Architecture 64-Bit ELF V2 ABI Specification
181 * https://members.openpowerfoundation.org/document/dl/576
183 * [4] Its unclear if "without any alignment gap" is hard ABI requirement,
184 * but we must follow this rule due to suboptimal _set_tp()
185 * (aka <ARCH>_SET_TP) implementation. This function doesn't expect TP but
188 * [5] I'm not able to validate "values are biased" assertions.
191 #define TLS_TCB_SIZE (2 * sizeof(void *))
194 * Return pointer to allocated TLS block
197 get_tls_block_ptr(void *tcb, size_t tcbsize)
199 size_t extra_size, post_size, pre_size, tls_block_size;
201 /* Compute fragments sizes. */
202 extra_size = tcbsize - TLS_TCB_SIZE;
203 #if defined(__aarch64__) || defined(__arm__)
204 post_size = roundup2(TLS_TCB_SIZE, tls_init_align) - TLS_TCB_SIZE;
208 tls_block_size = tcbsize + post_size;
209 pre_size = roundup2(tls_block_size, tls_init_align) - tls_block_size;
211 return ((char *)tcb - pre_size - extra_size);
215 * Free Static TLS using the Variant I method. The tcbsize
216 * and tcbalign parameters must be the same as those used to allocate
220 __libc_free_tls(void *tcb, size_t tcbsize, size_t tcbalign __unused)
225 tls = (Elf_Addr **)tcb;
227 __je_bootstrap_free(dtv);
228 free_aligned(get_tls_block_ptr(tcb, tcbsize));
232 * Allocate Static TLS using the Variant I method.
234 * To handle all above requirements, we setup the following layout for
236 * (whole memory block is aligned with MAX(TLS_TCB_ALIGN, tls_init_align))
238 * +----------+--------------+--------------+-----------+------------------+
239 * | pre gap | extended TCB | TCB | post gap | TLS segment |
240 * | pre_size | extra_size | TLS_TCB_SIZE | post_size | tls_static_space |
241 * +----------+--------------+--------------+-----------+------------------+
244 * extra_size is tcbsize - TLS_TCB_SIZE
245 * post_size is used to adjust TCB to TLS aligment for first version of TLS
246 * layout and is always 0 for second version.
247 * pre_size is used to adjust TCB aligment for first version and to adjust
248 * TLS alignment for second version.
252 __libc_allocate_tls(void *oldtcb, size_t tcbsize, size_t tcbalign)
254 Elf_Addr *dtv, **tcb;
255 char *tls_block, *tls;
256 size_t extra_size, maxalign, post_size, pre_size, tls_block_size;
258 if (oldtcb != NULL && tcbsize == TLS_TCB_SIZE)
261 tls_assert(tcbalign >= TLS_TCB_ALIGN);
262 maxalign = MAX(tcbalign, tls_init_align);
264 /* Compute fragmets sizes. */
265 extra_size = tcbsize - TLS_TCB_SIZE;
266 #if defined(__aarch64__) || defined(__arm__)
267 post_size = roundup2(TLS_TCB_SIZE, tls_init_align) - TLS_TCB_SIZE;
271 tls_block_size = tcbsize + post_size;
272 pre_size = roundup2(tls_block_size, tls_init_align) - tls_block_size;
273 tls_block_size += pre_size + tls_static_space;
275 /* Allocate whole TLS block */
276 tls_block = malloc_aligned(tls_block_size, maxalign);
277 if (tls_block == NULL) {
278 tls_msg("__libc_allocate_tls: Out of memory.\n");
281 memset(tls_block, 0, tls_block_size);
282 tcb = (Elf_Addr **)(tls_block + pre_size + extra_size);
283 tls = (char *)tcb + TLS_TCB_SIZE + post_size;
285 if (oldtcb != NULL) {
286 memcpy(tls_block, get_tls_block_ptr(oldtcb, tcbsize),
288 free_aligned(oldtcb);
290 /* Adjust the DTV. */
292 dtv[2] = (Elf_Addr)(tls + DTV_OFFSET);
294 dtv = __je_bootstrap_malloc(3 * sizeof(Elf_Addr));
296 tls_msg("__libc_allocate_tls: Out of memory.\n");
301 dtv[0] = 1; /* Generation. */
302 dtv[1] = 1; /* Segments count. */
303 dtv[2] = (Elf_Addr)(tls + DTV_OFFSET);
305 if (tls_init_size > 0)
306 memcpy(tls, tls_init, tls_init_size);
314 #ifdef TLS_VARIANT_II
316 #define TLS_TCB_SIZE (3 * sizeof(Elf_Addr))
319 * Free Static TLS using the Variant II method.
322 __libc_free_tls(void *tcb, size_t tcbsize __unused, size_t tcbalign)
326 Elf_Addr tlsstart, tlsend;
329 * Figure out the size of the initial TLS block so that we can
330 * find stuff which ___tls_get_addr() allocated dynamically.
332 tcbalign = MAX(tcbalign, tls_init_align);
333 size = roundup2(tls_static_space, tcbalign);
335 dtv = ((Elf_Addr**)tcb)[1];
336 tlsend = (Elf_Addr) tcb;
337 tlsstart = tlsend - size;
338 free_aligned((void*)tlsstart);
339 __je_bootstrap_free(dtv);
343 * Allocate Static TLS using the Variant II method.
346 __libc_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign)
351 Elf_Addr segbase, oldsegbase;
353 tcbalign = MAX(tcbalign, tls_init_align);
354 size = roundup2(tls_static_space, tcbalign);
356 if (tcbsize < 2 * sizeof(Elf_Addr))
357 tcbsize = 2 * sizeof(Elf_Addr);
358 tls = malloc_aligned(size + tcbsize, tcbalign);
360 tls_msg("__libc_allocate_tls: Out of memory.\n");
363 memset(tls, 0, size + tcbsize);
364 dtv = __je_bootstrap_malloc(3 * sizeof(Elf_Addr));
366 tls_msg("__libc_allocate_tls: Out of memory.\n");
370 segbase = (Elf_Addr)(tls + size);
371 ((Elf_Addr*)segbase)[0] = segbase;
372 ((Elf_Addr*)segbase)[1] = (Elf_Addr) dtv;
376 dtv[2] = segbase - tls_static_space;
380 * Copy the static TLS block over whole.
382 oldsegbase = (Elf_Addr) oldtls;
383 memcpy((void *)(segbase - tls_static_space),
384 (const void *)(oldsegbase - tls_static_space),
388 * We assume that this block was the one we created with
389 * allocate_initial_tls().
391 _rtld_free_tls(oldtls, 2*sizeof(Elf_Addr), sizeof(Elf_Addr));
393 memcpy((void *)(segbase - tls_static_space),
394 tls_init, tls_init_size);
395 memset((void *)(segbase - tls_static_space + tls_init_size),
396 0, tls_static_space - tls_init_size);
399 return (void*) segbase;
402 #endif /* TLS_VARIANT_II */
407 __libc_allocate_tls(void *oldtls __unused, size_t tcbsize __unused,
408 size_t tcbalign __unused)
414 __libc_free_tls(void *tcb __unused, size_t tcbsize __unused,
415 size_t tcbalign __unused)
421 extern char **environ;
428 Elf_Auxinfo *aux, *auxp;
434 sp = (Elf_Addr *) environ;
437 aux = (Elf_Auxinfo *) sp;
440 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
441 switch (auxp->a_type) {
443 phdr = auxp->a_un.a_ptr;
447 phent = auxp->a_un.a_val;
451 phnum = auxp->a_un.a_val;
455 if (phdr == NULL || phent != sizeof(Elf_Phdr) || phnum == 0)
458 for (i = 0; (unsigned) i < phnum; i++) {
459 if (phdr[i].p_type == PT_TLS) {
460 tls_static_space = roundup2(phdr[i].p_memsz,
462 tls_init_size = phdr[i].p_filesz;
463 tls_init_align = phdr[i].p_align;
464 tls_init = (void*) phdr[i].p_vaddr;
468 tls = _rtld_allocate_tls(NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN);