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#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;
}
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