This is a new flag that can be passed to recvmsg () to make it
atomically set the CLOEXEC flag on all the file descriptors received
using the SCM_RIGHTS mechanism. This is useful for all the same reasons
that the other XXX_CLOEXEC flags are useful: namely, it provides
atomicity with respect to another thread of the same process calling
(fork and then) exec at the same time.
This flag is already supported on Linux and FreeBSD. The flag's value,
0x40000, is choosen to match FreeBSD's.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230423160548.126576-2-bugaevc@gmail.com>
The flags are used by _hurd_intern_fd, which takes O_* flags, not FD_*.
Also, it is of no concern to the receiving process whether or not
the sender process wants to close its copy of sent file descriptor
upon exec, and it should not influence whether or not the received
file descriptor gets the FD_CLOEXEC flag set in the receiving process.
The latter should in fact be dependent on the MSG_CMSG_CLOEXEC flag
being passed to the recvmsg () call, which is going to be implemented
in the following commit.
Fixes 344e755248
"hurd: Support sending file descriptors over Unix sockets"
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
This makes the prefer_map_32bit_exec tunable no longer Linux-specific.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230423215526.346009-4-bugaevc@gmail.com>
This is a flag that can be passed to mmap () to request that the mapping
being established should be located in the lower 2 GB area of the
address space, so only the lower 31 (not 32) bits can be set in its
address, and the address can be represented as a 32-bit integer without
truncating it.
This flag is intended to be compatible with Linux, FreeBSD, and Darwin
flags of the same name. Out of those systems, it appears Linux and
FreeBSD take MAP_32BIT to mean "map 31 bit", whereas Darwin allows the
32nd bit to be set in the address as well. The Hurd follows Linux and
FreeBSD behavior.
Unlike on those systems, on the Hurd MAP_32BIT is defined on all
supported architectures (which currently are only i386 and x86_64).
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230423215526.346009-1-bugaevc@gmail.com>
When opening a temporary file without O_CLOEXEC we risk leaking the
file descriptor if another thread calls (fork and then) exec while we
have the fd open. Fix this by consistently passing O_CLOEXEC everywhere
where we open a file for internal use (and not to return it to the user,
in which case the API defines whether or not the close-on-exec flag
shall be set on the returned fd).
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230419160207.65988-4-bugaevc@gmail.com>
Properly differentiate between setting up the real TLS with
TLS_INIT_TP, and setting up the early TLS (__init1_tcbhead) in static
builds. In the latter case, don't yet migrate the reply port into the
TCB, and don't yet set __libc_tls_initialized to 1.
This also lets us move the __init1_desc assignment inside
_hurd_tls_init ().
Fixes cd019ddd89
"hurd: Don't leak __hurd_reply_port0"
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Created tunable glibc.pthread.stack_hugetlb to control when hugepages
can be used for stack allocation.
In case THP are enabled and glibc.pthread.stack_hugetlb is set to
0, glibc will madvise the kernel not to use allow hugepages for stack
allocations.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
We must not use the user's reply port (scp->sc_reply_port) for any of
our own RPCs, otherwise various things break. So, use MACH_PORT_DEAD as
a reply port when destroying our reply port, and make sure to do this
after _hurd_sigstate_unlock (), which may do a gsync_wake () RPC.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Optimize the fast paths (x < y) and (x/y < 2^12). Delay handling of special
cases to reduce the number of instructions executed before the fast paths.
Performance improvements for fmod:
Skylake Zen2 Neoverse V1
subnormals 11.8% 4.2% 11.5%
normal 3.9% 0.01% -0.5%
close-exponents 6.3% 5.6% 19.4%
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
When glibc is built as a shared library, TLS is always initialized by
the call of TLS_INIT_TP () macro made inside the dynamic loader, prior
to running the main program (see dl-call_tls_init_tp.h). We can take
advantage of this: we know for sure that __LIBC_NO_TLS () will evaluate
to 0 in all other cases, so let the compiler know that explicitly too.
Also, only define _hurd_tls_init () and TLS_INIT_TP () under the same
conditions (either !SHARED or inside rtld), to statically assert that
this is the case.
Other than a microoptimization, this also helps with avoiding awkward
sharing of the __libc_tls_initialized variable between ld.so and libc.so
that we would have to do otherwise -- we know for sure that no sharing
is required, simply because __libc_tls_initialized would always be set
to true inside libc.so.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230319151017.531737-25-bugaevc@gmail.com>
Now that the signal code no longer accesses it, the only real user of it
was mig-reply.c, so move the logic for managing the port there.
If we're in SHARED and outside of rtld, we know that __LIBC_NO_TLS ()
always evaluates to 0, and a TLS reply port will always be used, not
__hurd_reply_port0. Still, the compiler does not see that
__hurd_reply_port0 is never used due to its address being taken. To deal
with this, explicitly compile out __hurd_reply_port0 when we know we
won't use it.
Also, instead of accessing the port via THREAD_SELF->reply_port, this
uses THREAD_GETMEM and THREAD_SETMEM directly, avoiding possible
miscompilations.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
This reverts commit b37899d34d.
Apparently we load libc.so (and thus start using its functions) before
calling TLS_INIT_TP, so libc.so functions should not actually assume
that TLS is always set up.
Previously, once we set up TLS, we would implicitly switch from using
__hurd_reply_port0 to reply_port inside the TCB, leaving the former
unused. But we never deallocated it, so it got leaked.
Instead, migrate the port into the new TCB's reply_port slot. This
avoids both the port leak and an extra syscall to create a new reply
port for the TCB.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230319151017.531737-28-bugaevc@gmail.com>
If we're doing signals, that means we've already got the signal thread
running, and that implies TLS having been set up. So we know that
__hurd_local_reply_port will resolve to THREAD_SELF->reply_port, and can
access that directly using the THREAD_GETMEM and THREAD_SETMEM macros.
This avoids potential miscompilations, and should also be a tiny bit
faster.
Also, use mach_port_mod_refs () and not mach_port_destroy () to destroy
the receive right. mach_port_destroy () should *never* be used on
mach_task_self (); this can easily lead to port use-after-free
vulnerabilities if the task has any other references to the same port.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230319151017.531737-26-bugaevc@gmail.com>
When glibc is built as a shared library, TLS is always initialized by
the call of TLS_INIT_TP () macro made inside the dynamic loader, prior
to running the main program (see dl-call_tls_init_tp.h). We can take
advantage of this: we know for sure that __LIBC_NO_TLS () will evaluate
to 0 in all other cases, so let the compiler know that explicitly too.
Also, only define _hurd_tls_init () and TLS_INIT_TP () under the same
conditions (either !SHARED or inside rtld), to statically assert that
this is the case.
Other than a microoptimization, this also helps with avoiding awkward
sharing of the __libc_tls_initialized variable between ld.so and libc.so
that we would have to do otherwise -- we know for sure that no sharing
is required, simply because __libc_tls_initialized would always be set
to true inside libc.so.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230319151017.531737-25-bugaevc@gmail.com>
These are just regular local variables that are not accessed in any
funny ways, not even though a pointer. There's absolutely no reason to
declare them volatile. It only ends up hurting the quality of the
generated machine code.
If anything, it would make sense to decalre sigsp as *pointing* to
volatile memory (volatile void *sigsp), but evidently that's not needed
either.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230403115621.258636-2-bugaevc@gmail.com>
This is based on the Linux port's version, but laid out to match Mach's
struct i386_thread_state, much like the i386 version does.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Rename x86_cpu_INDEX_7_ECX_1 to x86_cpu_INDEX_7_ECX_15 for the unused bit
15 in ECX from CPUID with EAX == 0x7 and ECX == 0.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
