From 8431d7972fd9be0fdcaff8516316d748e81724bb Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 4 Oct 2012 16:35:46 -0400 Subject: [PATCH] TLS (GNU/C11 thread-local storage) support for static-linked programs the design for TLS in dynamic-linked programs is mostly complete too, but I have not yet implemented it. cost is nonzero but still low for programs which do not use TLS and/or do not use threads (a few hundred bytes of new code, plus dependency on memcpy). i believe it can be made smaller at some point by merging __init_tls and __init_security into __libc_start_main and avoiding duplicate auxv-parsing code. at the same time, I've also slightly changed the logic pthread_create uses to allocate guard pages to ensure that guard pages are not counted towards commit charge. --- src/env/__init_tls.c | 71 +++++++++++++++++++++++++++++++++++++ src/env/__libc_start_main.c | 2 ++ src/internal/libc.h | 1 + src/ldso/dynlink.c | 10 ++++++ src/thread/pthread_create.c | 23 +++++++++--- src/thread/pthread_self.c | 24 ++++++++----- 6 files changed, 117 insertions(+), 14 deletions(-) create mode 100644 src/env/__init_tls.c diff --git a/src/env/__init_tls.c b/src/env/__init_tls.c new file mode 100644 index 00000000..4a840cf2 --- /dev/null +++ b/src/env/__init_tls.c @@ -0,0 +1,71 @@ +#include +#include +#include "pthread_impl.h" +#include "libc.h" +#include "atomic.h" + +#ifndef SHARED + +static void *image; +static size_t len, bss, align; + +void *__copy_tls(unsigned char *mem, size_t cnt) +{ + mem += ((uintptr_t)image - (uintptr_t)mem) & (align-1); + memcpy(mem, image, len); + return mem + len + bss; +} + +static void *simple(void *p) +{ + *(void **)p = p; + return __set_thread_area(p) ? 0 : p; +} + +weak_alias(simple, __install_initial_tls); + +void *__mmap(void *, size_t, int, int, int, off_t); + +#if ULONG_MAX == 0xffffffff +typedef Elf32_Phdr Phdr; +#else +typedef Elf64_Phdr Phdr; +#endif + +#define AUX_CNT 6 + +void __init_tls(size_t *auxv) +{ + size_t i, aux[AUX_CNT] = { 0 }; + unsigned char *p, *mem; + size_t n, d; + Phdr *phdr, *tls_phdr=0; + size_t base = 0; + + for (; auxv[0]; auxv+=2) if (auxv[0]p_type == PT_PHDR) + base = aux[AT_PHDR] - phdr->p_vaddr; + if (phdr->p_type == PT_TLS) + tls_phdr = phdr; + } + if (!tls_phdr) return; + + libc.tls_size = len+bss+align+4*sizeof(size_t)+sizeof(struct pthread); + + image = (void *)(base + tls_phdr->p_vaddr); + len = tls_phdr->p_filesz; + bss = tls_phdr->p_memsz - len; + align = tls_phdr->p_align; + if (align < 4*sizeof(size_t)) align = 4*sizeof(size_t); + mem = __mmap(0, libc.tls_size, PROT_READ|PROT_WRITE, + MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); + if (mem == MAP_FAILED) a_crash(); + + if (!__install_initial_tls(__copy_tls(mem, 0))) a_crash(); +} +#else +void __init_tls(size_t *auxv) { } +#endif diff --git a/src/env/__libc_start_main.c b/src/env/__libc_start_main.c index f31222b2..a38569d5 100644 --- a/src/env/__libc_start_main.c +++ b/src/env/__libc_start_main.c @@ -1,5 +1,6 @@ #include "libc.h" +void __init_tls(size_t *); void __init_security(size_t *); int __libc_start_main( @@ -15,6 +16,7 @@ int __libc_start_main( libc.ldso_fini = ldso_fini; libc.fini = fini; + __init_tls((void *)auxv); __init_security((void *)auxv); /* Execute constructors (static) linked into the application */ diff --git a/src/internal/libc.h b/src/internal/libc.h index ea863d67..ca06f319 100644 --- a/src/internal/libc.h +++ b/src/internal/libc.h @@ -16,6 +16,7 @@ struct __libc { int canceldisable; FILE *ofl_head; int ofl_lock[2]; + volatile size_t tls_size, tls_cnt; }; extern size_t __hwcap; diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c index 960e0898..1447e205 100644 --- a/src/ldso/dynlink.c +++ b/src/ldso/dynlink.c @@ -17,6 +17,9 @@ #include #include #include +#include "pthread_impl.h" +#include "libc.h" +#undef libc static int errflag; static char errbuf[128]; @@ -788,6 +791,8 @@ void *__dynlink(int argc, char **argv) debug.state = 0; _dl_debug_state(); + /* Stand-in until real TLS support is added to dynamic linker */ + __libc.tls_size = sizeof(struct pthread) + 4*sizeof(size_t); if (ssp_used) __init_ssp(auxv); do_init_fini(tail); @@ -802,6 +807,11 @@ void *__dynlink(int argc, char **argv) return (void *)aux[AT_ENTRY]; } +void *__copy_tls(unsigned char *mem, size_t cnt) +{ + return mem; +} + void *dlopen(const char *file, int mode) { struct dso *volatile p, *orig_tail = tail, *next; diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c index d8b8f0fc..f53fc1ba 100644 --- a/src/thread/pthread_create.c +++ b/src/thread/pthread_create.c @@ -84,6 +84,8 @@ static void init_file_lock(FILE *f) if (f && f->lock<0) f->lock = 0; } +void *__copy_tls(unsigned char *, size_t); + int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr, void *(*entry)(void *), void *restrict arg) { int ret; @@ -92,6 +94,8 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr, struct pthread *self = pthread_self(), *new; unsigned char *map, *stack, *tsd; unsigned flags = 0x7d8f00; + size_t tls_cnt = libc.tls_cnt; + size_t tls_size = libc.tls_size; if (!self) return ENOSYS; if (!libc.threaded) { @@ -109,15 +113,24 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr, } else { if (attr) { guard = ROUND(attr->_a_guardsize + DEFAULT_GUARD_SIZE); - size = guard + ROUND(attr->_a_stacksize + DEFAULT_STACK_SIZE); + size = guard + ROUND(attr->_a_stacksize + + DEFAULT_STACK_SIZE + tls_size); } size += __pthread_tsd_size; - map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); - if (map == MAP_FAILED) return EAGAIN; - if (guard) mprotect(map, guard, PROT_NONE); + if (guard) { + map = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0); + if (map == MAP_FAILED) return EAGAIN; + if (mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)) { + munmap(map, size); + return EAGAIN; + } + } else { + map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0); + if (map == MAP_FAILED) return EAGAIN; + } tsd = map + size - __pthread_tsd_size; } - new = (void *)(tsd - sizeof *new - PAGE_SIZE%sizeof *new); + new = __copy_tls(tsd - tls_size, tls_cnt); new->map_base = map; new->map_size = size; new->pid = self->pid; diff --git a/src/thread/pthread_self.c b/src/thread/pthread_self.c index a8cc80b5..a93d8129 100644 --- a/src/thread/pthread_self.c +++ b/src/thread/pthread_self.c @@ -1,6 +1,6 @@ #include "pthread_impl.h" -static struct pthread main_thread; +static struct pthread *main_thread = &(struct pthread){0}; /* pthread_key_create.c overrides this */ static const void *dummy[1] = { 0 }; @@ -10,14 +10,14 @@ static int init_main_thread() { __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, __SYSCALL_SSLEN); - if (__set_thread_area(&main_thread) < 0) return -1; - main_thread.canceldisable = libc.canceldisable; - main_thread.tsd = (void **)__pthread_tsd_main; - main_thread.errno_ptr = __errno_location(); - main_thread.self = &main_thread; - main_thread.tid = main_thread.pid = - __syscall(SYS_set_tid_address, &main_thread.tid); - libc.main_thread = &main_thread; + if (__set_thread_area(main_thread) < 0) return -1; + main_thread->canceldisable = libc.canceldisable; + main_thread->tsd = (void **)__pthread_tsd_main; + main_thread->errno_ptr = __errno_location(); + main_thread->self = main_thread; + main_thread->tid = main_thread->pid = + __syscall(SYS_set_tid_address, &main_thread->tid); + libc.main_thread = main_thread; return 0; } @@ -35,3 +35,9 @@ pthread_t __pthread_self_def() weak_alias(__pthread_self_def, pthread_self); weak_alias(__pthread_self_def, __pthread_self_init); + +void *__install_initial_tls(void *p) +{ + main_thread = p; + return __pthread_self_def(); +} -- 2.25.1