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-rw-r--r--src/thread/pthread_create.c189
1 files changed, 189 insertions, 0 deletions
diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
new file mode 100644
index 00000000..6fa484c7
--- /dev/null
+++ b/src/thread/pthread_create.c
@@ -0,0 +1,189 @@
+#include "pthread_impl.h"
+
+#define pthread_self __pthread_self
+
+static void docancel(struct pthread *self)
+{
+ struct __ptcb cb = { .__next = self->cancelbuf };
+ __pthread_unwind_next(&cb);
+}
+
+static void cancel_handler(int sig, siginfo_t *si, void *ctx)
+{
+ struct pthread *self = pthread_self();
+ self->cancel = 1;
+ if (self->canceldisable || (!self->cancelasync && !self->cancelpoint))
+ return;
+ docancel(self);
+}
+
+/* "rsyscall" is a mechanism by which a thread can synchronously force all
+ * other threads to perform an arbitrary syscall. It is necessary to work
+ * around the non-conformant implementation of setuid() et al on Linux,
+ * which affect only the calling thread and not the whole process. This
+ * implementation performs some tricks with signal delivery to work around
+ * the fact that it does not keep any list of threads in userspace. */
+
+static struct {
+ volatile int lock, hold, blocks, cnt;
+ unsigned long arg[6];
+ int nr;
+ int err;
+} rs;
+
+static void rsyscall_handler(int sig, siginfo_t *si, void *ctx)
+{
+ if (rs.cnt == libc.threads_minus_1) return;
+
+ if (syscall6(rs.nr, rs.arg[0], rs.arg[1], rs.arg[2],
+ rs.arg[3], rs.arg[4], rs.arg[5]) < 0 && !rs.err) rs.err=errno;
+
+ a_inc(&rs.cnt);
+ __wake(&rs.cnt, 1, 1);
+ while(rs.hold)
+ __wait(&rs.hold, 0, 1, 1);
+ a_dec(&rs.cnt);
+ if (!rs.cnt) __wake(&rs.cnt, 1, 1);
+}
+
+static int rsyscall(int nr, long a, long b, long c, long d, long e, long f)
+{
+ int i, ret;
+ sigset_t set = { 0 };
+ struct pthread *self = pthread_self();
+ sigaddset(&set, SIGSYSCALL);
+
+ LOCK(&rs.lock);
+ while ((i=rs.blocks))
+ __wait(&rs.blocks, 0, i, 1);
+
+ __libc_sigprocmask(SIG_BLOCK, &set, 0);
+
+ rs.nr = nr;
+ rs.arg[0] = a; rs.arg[1] = b;
+ rs.arg[2] = c; rs.arg[3] = d;
+ rs.arg[4] = d; rs.arg[5] = f;
+ rs.hold = 1;
+ rs.err = 0;
+ rs.cnt = 0;
+
+ /* Dispatch signals until all threads respond */
+ for (i=libc.threads_minus_1; i; i--)
+ sigqueue(self->pid, SIGSYSCALL, (union sigval){0});
+ while ((i=rs.cnt) < libc.threads_minus_1) {
+ sigqueue(self->pid, SIGSYSCALL, (union sigval){0});
+ __wait(&rs.cnt, 0, i, 1);
+ }
+
+ /* Handle any lingering signals with no-op */
+ __libc_sigprocmask(SIG_UNBLOCK, &set, 0);
+
+ /* Resume other threads' signal handlers and wait for them */
+ rs.hold = 0;
+ __wake(&rs.hold, -1, 0);
+ while((i=rs.cnt)) __wait(&rs.cnt, 0, i, 1);
+
+ if (rs.err) errno = rs.err, ret = -1;
+ else ret = syscall6(nr, a, b, c, d, e, f);
+
+ UNLOCK(&rs.lock);
+ return ret;
+}
+
+static void cancelpt(int x)
+{
+ struct pthread *self = pthread_self();
+ if (self->canceldisable) return;
+ self->cancelpoint = x;
+ if (self->cancel) docancel(self);
+}
+
+static void init_threads()
+{
+ struct sigaction sa = { .sa_flags = SA_SIGINFO | SA_RESTART };
+ libc.lock = __lock;
+ libc.cancelpt = cancelpt;
+ libc.rsyscall = rsyscall;
+ sa.sa_sigaction = cancel_handler;
+ __libc_sigaction(SIGCANCEL, &sa, 0);
+ sigaddset(&sa.sa_mask, SIGSYSCALL);
+ sigaddset(&sa.sa_mask, SIGCANCEL);
+ sa.sa_sigaction = rsyscall_handler;
+ __libc_sigaction(SIGSYSCALL, &sa, 0);
+ sigprocmask(SIG_UNBLOCK, &sa.sa_mask, 0);
+}
+
+static int start(void *p)
+{
+ struct pthread *self = p;
+ pthread_exit(self->start(self->start_arg));
+ return 0;
+}
+
+#undef pthread_self
+
+#define CLONE_MAGIC 0x7d0f00
+int __clone(int (*)(void *), void *, int, void *, pid_t *, void *, pid_t *);
+
+#define ROUND(x) (((x)+PAGE_SIZE-1)&-PAGE_SIZE)
+
+/* pthread_key_create.c overrides this */
+static const size_t dummy = 0;
+weak_alias(dummy, __pthread_tsd_size);
+
+int pthread_create(pthread_t *res, const pthread_attr_t *attr, void *(*entry)(void *), void *arg)
+{
+ static int init;
+ int ret;
+ size_t size, guard;
+ struct pthread *self = pthread_self(), *new;
+ unsigned char *map, *stack, *tsd;
+ static const pthread_attr_t default_attr;
+
+ if (!self) return errno = ENOSYS;
+ if (!init && ++init) init_threads();
+
+ if (!attr) attr = &default_attr;
+ guard = ROUND(attr->__guardsize + DEFAULT_GUARD_SIZE);
+ size = guard + ROUND(attr->__stacksize + DEFAULT_STACK_SIZE);
+ size += __pthread_tsd_size;
+ map = mmap(0, size, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANON, -1, 0);
+ if (!map) return EAGAIN;
+ mprotect(map, guard, PROT_NONE);
+
+ tsd = map + size - __pthread_tsd_size;
+ new = (void *)(tsd - sizeof *new - PAGE_SIZE%sizeof *new);
+ new->map_base = map;
+ new->map_size = size;
+ new->pid = self->pid;
+ new->errno_ptr = &new->errno_val;
+ new->start = entry;
+ new->start_arg = arg;
+ new->self = new;
+ new->tsd = (void *)tsd;
+ new->detached = attr->__detach;
+ new->attr = *attr;
+ memcpy(new->tlsdesc, self->tlsdesc, sizeof new->tlsdesc);
+ new->tlsdesc[1] = (uintptr_t)new;
+ stack = (void *)((uintptr_t)new-1 & ~(uintptr_t)15);
+
+ /* We must synchronize new thread creation with rsyscall
+ * delivery. This looks to be the least expensive way: */
+ a_inc(&rs.blocks);
+ while (rs.lock) __wait(&rs.lock, 0, 1, 1);
+
+ a_inc(&libc.threads_minus_1);
+ ret = __clone(start, stack, CLONE_MAGIC, new,
+ &new->tid, &new->tlsdesc, &new->tid);
+
+ a_dec(&rs.blocks);
+ if (rs.lock) __wake(&rs.blocks, 1, 1);
+
+ if (ret < 0) {
+ a_dec(&libc.threads_minus_1);
+ munmap(map, size);
+ return -ret;
+ }
+ *res = new;
+ return 0;
+}