As discussed in libc-alpha [1] current clone with CLONE_VM (without
CLONE_THREAD set) will reset the pthread pid/tid fields to -1. The
issue is since memory is shared between the parent and child it will
clobber parent's cached pid/tid leading to internal inconsistencies
if the value is not restored.
And even it is restored it may lead to racy conditions when between
set/restore a thread might invoke pthread function that validate the
pthread with INVALID_TD_P/INVALID_NOT_TERMINATED_TD_P and thus get
wrong results.
As stated in BZ19957, previously reports of this behaviour was close
with EWONTFIX due the fact usage of clone outside glibc is tricky
since glibc requires consistent internal pthread, while using clone
directly may not provide it. However since now posix_spawn uses
clone (CLONE_VM) to fixes various issues related to previous vfork
usage this issue requires fixing.
The vfork implementation also does something similar, but instead
it negates and restores only the *pid* field and functions that
might access its value know to handle such case (getpid, raise
and pthread ones that uses INVALID_TD_P/INVALID_NOT_TERMINATED_TD_P
macros that check only *tid* field). Also vfork does not call
__clone directly, instead calling either __NR_vfork or __NR_clone
directly.
So this patch removes this clone behavior by avoiding setting
the pthread pid/tid field for CLONE_VM. There is no need to
check for CLONE_THREAD, since the minimum supported kernel in all
architecture implies that CLONE_VM must be used with CLONE_THREAD,
otherwise clone returns EINVAL.
Instead of current approach of:
int clone(int (*fn)(void *), void *child_stack, int flags, ...)
[...]
if (flags & CLONE_THREAD)
goto do_syscall;
pid_t new_value;
if (flags & CLONE_VM)
new_value = -1;
else
new_value = getpid ();
THREAD_SETMEM (THREAD_SELF, pid, new_value);
THREAD_SETMEM (THREAD_SELF, tid, new_value);
do_syscall:
[...]
The new approach uses:
int clone(int (*fn)(void *), void *child_stack, int flags, ...)
[...]
if (flags & CLONE_VM)
goto do_syscall;
pid_t new_value = getpid ();
THREAD_SETMEM (THREAD_SELF, pid, new_value);
THREAD_SETMEM (THREAD_SELF, tid, new_value);
do_syscall:
[...]
It also removes the linux tst-getpid2.c test which expects the previous
behavior and instead add another clone test.
Tested on x86_64, i686, x32, powerpc64le, aarch64, armhf, s390, and
s390x. I also did limited check on mips32 and sparc64 (using the new
added test).
I also got reviews from both m68k, hppa, and tile. So I presume for
these architecture the patch works.
The fixes for alpha, microblaze, sh, ia64, and nio2 have not been
tested.
[1] https://sourceware.org/ml/libc-alpha/2016-04/msg00307.html
* sysdeps/unix/sysv/linux/Makefile [$(subdir) == nptl] (test): Remove
tst-getpid2.
(test): Add tst-clone2.
* sysdeps/unix/sysv/linux/tst-clone2.c: New file.
* sysdeps/unix/sysv/linux/aarch64/clone.S (__clone): Do not change
pid/tid fields for CLONE_VM.
* sysdeps/unix/sysv/linux/arm/clone.S: Likewise.
* sysdeps/unix/sysv/linux/i386/clone.S: Likewise.
* sysdeps/unix/sysv/linux/mips/clone.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/clone.S: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/x86_64/clone.S: Likewise.
* sysdeps/unix/sysv/linux/tst-getpid2.c: Remove file.
This patch implements a new posix_spawn{p} implementation for Linux. The main
difference is it uses the clone syscall directly with CLONE_VM and CLONE_VFORK
flags and a direct allocated stack. The new stack and start function solves
most the vfork limitation (possible parent clobber due stack spilling). The
remaning issue are related to signal handling:
1. That no signal handlers must run in child context, to avoid corrupt
parent's state.
2. Child must synchronize with parent to enforce stack deallocation and
to possible return execv issues.
The first one is solved by blocking all signals in child, even NPTL-internal
ones (SIGCANCEL and SIGSETXID). The second issue is done by a stack allocation
in parent and a synchronization with using a pipe or waitpid (in case or error).
The pipe has the advantage of allowing the child signal an exec error (checked
with new tst-spawn2 test).
There is an inherent race condition in pipe2 usage for architectures that do not
support the syscall directly. In such cases the a pipe plus fctnl is used
instead and it may lead to file descriptor leak in parent (as decribed by fcntl
documentation).
The child process stack is allocate with a mmap with MAP_STACK flag using
default architecture stack size. Although it is slower than use a stack buffer
from parent, it allows some slack for the compatibility code to run scripts
with no shebang (which may use a buffer with size depending of argument list
count).
Performance should be similar to the vfork default posix implementation and
way faster than fork path (vfork on mostly linux ports are basically
clone with CLONE_VM plus CLONE_VFORK). The only difference is the syscalls
required for the stack allocation/deallocation.
It fixes BZ#10354, BZ#14750, and BZ#18433.
Tested on i386, x86_64, powerpc64le, and aarch64.
[BZ #14750]
[BZ #10354]
[BZ #18433]
* include/sched.h (__clone): Add hidden prototype.
(__clone2): Likewise.
* include/unistd.h (__dup): Likewise.
* posix/Makefile (tests): Add tst-spawn2.
* posix/tst-spawn2.c: New file.
* sysdeps/posix/dup.c (__dup): Add hidden definition.
* sysdeps/unix/sysv/linux/aarch64/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/alpha/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/arm/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/hppa/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/i386/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/ia64/clone2.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/m68k/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/microblaze/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/mips/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/nios2/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S (__clone):
Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S (__clone):
Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/sh/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/tile/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/x86_64/clone.S (__clone): Likewise.
* sysdeps/unix/sysv/linux/nptl-signals.h
(____nptl_is_internal_signal): New function.
* sysdeps/unix/sysv/linux/spawni.c: New file.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: Correct stack
alignment. Clean up flag bit tests.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S: Correct stack
alignment. Clean up flag bit tests. Remove redundent SP assignment.
Add TOC register save/restore around function call.
2002-07-29 Steven Munroe <sjmunroe@us.ibm.com>
* sysdeps/powerpc/__longjmp.S: Moved to...
* sysdeps/powerpc/powerpc32/__longjmp.S: ...here.
* sysdeps/powerpc/add_n.S: Moved to...
* sysdeps/powerpc/powerpc32/add_n.S: ...here.
* sysdeps/powerpc/addmul_1.S: Moved to...
* sysdeps/powerpc/powerpc32/addmul_1.S: ...here.
* sysdeps/powerpc/atomicity.h: Moved to...
* sysdeps/powerpc/powerpc32/atomicity.h: ...here.
* sysdeps/powerpc/backtrace.c: Moved to...
* sysdeps/powerpc/powerpc32/backtrace.c: ...here.
* sysdeps/powerpc/bp-asm.h: Moved to...
* sysdeps/powerpc/powerpc32/bp-asm.h: ...here.
* sysdeps/powerpc/bsd-_setjmp.S: Moved to...
* sysdeps/powerpc/powerpc32/bsd-_setjmp.S: ...here.
* sysdeps/powerpc/bsd-setjmp.S: Moved to...
* sysdeps/powerpc/powerpc32/bsd-setjmp.S: ...here.
* sysdeps/powerpc/dl-machine.c: Moved to...
* sysdeps/powerpc/powerpc32/dl-machine.c: ...here.
* sysdeps/powerpc/dl-machine.h: Moved to...
* sysdeps/powerpc/powerpc32/dl-machine.h: ...here.
* sysdeps/powerpc/dl-start.S: Moved to...
* sysdeps/powerpc/powerpc32/dl-start.S: ...here.
* sysdeps/powerpc/gprrest0.S: Moved to...
* sysdeps/powerpc/powerpc32/gprrest0.S: ...here.
* sysdeps/powerpc/gprrest1.S: Moved to...
* sysdeps/powerpc/powerpc32/gprrest1.S: ...here.
* sysdeps/powerpc/gprsave0.S: Moved to...
* sysdeps/powerpc/powerpc32/gprsave0.S: ...here.
* sysdeps/powerpc/gprsave1.S: Moved to...
* sysdeps/powerpc/powerpc32/gprsave1.S: ...here.
* sysdeps/powerpc/lshift.S: Moved to...
* sysdeps/powerpc/powerpc32/lshift.S: ...here.
* sysdeps/powerpc/memset.S: Moved to...
* sysdeps/powerpc/powerpc32/memset.S: ...here.
* sysdeps/powerpc/mul_1.S: Moved to...
* sysdeps/powerpc/powerpc32/mul_1.S: ...here.
* sysdeps/powerpc/ppc-mcount.S: Moved to...
* sysdeps/powerpc/powerpc32/ppc-mcount.S: ...here.
* sysdeps/powerpc/register-dump.h: Moved to...
* sysdeps/powerpc/powerpc32/register-dump.h: ...here.
* sysdeps/powerpc/rshift.S: Moved to...
* sysdeps/powerpc/powerpc32/rshift.S: ...here.
* sysdeps/powerpc/setjmp.S: Moved to...
* sysdeps/powerpc/powerpc32/setjmp.S: ...here.
* sysdeps/powerpc/stpcpy.S: Moved to...
* sysdeps/powerpc/powerpc32/stpcpy.S: ...here.
* sysdeps/powerpc/strchr.S: Moved to...
* sysdeps/powerpc/powerpc32/strchr.S: ...here.
* sysdeps/powerpc/strcmp.S: Moved to...
* sysdeps/powerpc/powerpc32/strcmp.S: ...here.
* sysdeps/powerpc/strcpy.S: Moved to...
* sysdeps/powerpc/powerpc32/strcpy.S: ...here.
* sysdeps/powerpc/strlen.S: Moved to...
* sysdeps/powerpc/powerpc32/strlen.S: ...here.
* sysdeps/powerpc/sub_n.S: Moved to...
* sysdeps/powerpc/powerpc32/sub_n.S: ...here.
* sysdeps/powerpc/submul_1.S: Moved to...
* sysdeps/powerpc/powerpc32/submul_1.S: ...here.
* sysdeps/powerpc/elf/bzero.S: Moved to...
* sysdeps/powerpc/powerpc32/elf/bzero.S: ...here.
* sysdeps/powerpc/elf/start.S: Moved to...
* sysdeps/powerpc/powerpc32/elf/start.S: ...here.
* sysdeps/powerpc/fpu/__longjmp.S: Moved to...
* sysdeps/powerpc/powerpc32/fpu/__longjmp.S: ...here.
* sysdeps/powerpc/fpu/fprrest.S: Moved to...
* sysdeps/powerpc/powerpc32/fpu/fprrest.S: ...here.
* sysdeps/powerpc/fpu/fprsave.S: Moved to...
* sysdeps/powerpc/powerpc32/fpu/fprsave.S: ...here.
* sysdeps/powerpc/fpu/setjmp.S: Moved to...
* sysdeps/powerpc/powerpc32/fpu/setjmp.S: ...here.
* sysdeps/powerpc/fpu/s_copysign.S: Moved to...
* sysdeps/powerpc/powerpc32/fpu/s_copysign.S: ...here.
* sysdeps/powerpc/fpu/s_copysignf.S: Moved to...
* sysdeps/powerpc/powerpc32/fpu/s_copysignf.S: ...here.
* sysdeps/unix/sysv/linux/powerpc/brk.S: Moved to...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/brk.S: ...here.
* sysdeps/unix/sysv/linux/powerpc/clone.S: Moved to...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: ...here.
* sysdeps/unix/sysv/linux/powerpc/glob64.c: Moved to...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/glob64.c: ...here.
* sysdeps/unix/sysv/linux/powerpc/kernel_stat.h: Moved to...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/kernel_stat.h: ...here.
* sysdeps/unix/sysv/linux/powerpc/socket.S: Moved to...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/socket.S: ...here.
* sysdeps/unix/sysv/linux/powerpc/sysdep.h: Moved to...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h: ...here.
* sysdeps/unix/sysv/linux/powerpc/syscalls.list: Moved to...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/syscalls.list: ...here.
Support PowerPC64. Separate powerpc into powerpc/powerpc32 and
powerpc/powerpc64.
2002-07-29 Steven Munroe <sjmunroe@us.ibm.com>
* FAQ.in: Add powerpc64 to supported targets list. Also state the
minimum gcc version is 3.2
* README: Add powerpc64 to supported targets list.
* configure.in: Change machine=powerpc to machine=powerpc/powerpc32.
Add powerpc64 and machine=powerpc/powerpc64.
(HAVE_ASM_GLOBAL_DOT_NAME): Define if linux*powerpc/powerpc64*.
* shlib-versions: Set DEFAULT version to 2.2.5 for powerpc64.
* sysdeps/powerpc/Dist: Remove dl-machine.c, dl-start.S, ppc-mcount.S,
gprsave1.S, gprsave0.S, gprrest1.S, and gprrest0.S.
* sysdeps/powerpc/powerpc32/Dist: New file.
* sysdeps/powerpc/Implies: Remove wordsize-32 and powerpc/soft-fp.
* sysdeps/powerpc/powerpc32/Implies: New file.
* sysdeps/powerpc/Makefile(cflags): Remove powerpc32 specific cflags.
($(with-fp) = no): Move test to powerpc32/Makefile.
($(subdir) = misc): Move to powerpc32/Makefile.
($(build-shared) = yes): Move to powerpc32/Makefile.
($(subdir) = csu): Move to powerpc32/Makefile.
(sysdep-rtld-routines): Remove dl-start. Moved these bits to ...
* sysdeps/powerpc/powerpc32/Makefile: New file.
* sysdeps/powerpc/Versions: Remove libgcc functions.
* sysdeps/powerpc/powerpc32/Versions: New file.
* sysdeps/powerpc/fpu/Makefile: Remove fprsave and fprrest.
* sysdeps/powerpc/powerpc32/fpu/Makefile: New file.
* sysdeps/unix/sysv/linux/configure.in (powerpc*):
Set arch_minimum_kernel=2.4.19 for powerpc/powerpc64. Also set
libc_cv_gcc_unwind_find_fde=yes only if !powerpc/powerpc64.
($machine): Add powerpc/powerpc64 to if ... | for
libc_cv_slibdir=/libc64.
(powerpc*): Set ldd_rewrite_script.
* sysdeps/unix/sysv/linux/powerpc/ldd-rewrite.sed: New file.
* sysdeps/unix/sysv/linux/powerpc/Dist: Remove clone.S.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/Dist: New file.
Add clone.S.
* sysdeps/unix/sysv/linux/powerpc/Makefile: Remove oldgetrlimit64.
* sysdeps/unix/sysv/linux/powerpc/Versions: Remove GLIBC_2.0
functions. Remove GLIBC_2.2 functions except getrlimit and
setrlimit. Moved them to ...
* sysdeps/unix/sysv/linux/powerpc/powerpc32/Versions: New file.
2002-09-04 Ulrich Drepper <drepper@redhat.com>
* libio/tst-atime.c: Include <errno.h>.
(do_test): Only perform fstatvfs check if ST_NOATIME is defined.
2002-09-03 Isamu Hasegawa <isamu@yamato.ibm.com>
* posix/regcomp.c (regcomp): Append "__restrict" modifier to avoid
warnings of some compilers.
(build_collating_symbol): Change the type of characters from
"unsigned char" to "char", and append a cast to "char*" pointer in
array subscript.
(build_collating_symbol): Likewise.
(build_equiv_class): Likewise.
(build_charclass): Likewise.
(re_compile_pattern): Remove incorrect cast.
(re_compile_fastmap_iter): Change the type of characters from
"unsigned char" to "char", and append a cast to "char*" pointer
in array subscript.
(parse_bracket_exp): Likewise.
* posix/regex_internal.c (re_string_construct_common): Likewise.
(re_string_allocate): Likewise.
(re_string_construct): Likewise.
(re_string_realloc_buffers): Likewise.
(build_wcs_buffer): Likewise.
(re_string_reconstruct): Likewise.
* posix/regex_internal.h: Change the type of characters in
re_string_t and bracket_elem_t from "unsigned char" to "char".
* posix/regexec.c (regexec): Append "__restrict" modifier to avoid
warnings of some compilers.
(transit_state_bkref_loop): Change the type of characters from
"unsigned char" to "char", and append a cast to "char*" pointer in
array subscript.
(check_node_accept_bytes): Likewise.
(find_collation_sequence_value): Likewise.
