Linux 6.13 (662df3e5c3766) added a lightweight way to define guard areas
through madvise syscall. Instead of PROT_NONE the guard region through
mprotect, userland can madvise the same area with a special flag, and
the kernel ensures that accessing the area will trigger a SIGSEGV (as for
PROT_NONE mapping).
The madvise way has the advantage of less kernel memory consumption for
the process page-table (one less VMA per guard area), and slightly less
contention on kernel (also due to the fewer VMA areas being tracked).
The pthread_create allocates a new thread stack in two ways: if a guard
area is set (the default) it allocates the memory range required using
PROT_NONE and then mprotect the usable stack area. Otherwise, if a
guard page is not set it allocates the region with the required flags.
For the MADV_GUARD_INSTALL support, the stack area region is allocated
with required flags and then the guard region is installed. If the
kernel does not support it, the usual way is used instead (and
MADV_GUARD_INSTALL is disabled for future stack creations).
The stack allocation strategy is recorded on the pthread struct, and it
is used in case the guard region needs to be resized. To avoid needing
an extra field, the 'user_stack' is repurposed and renamed to 'stack_mode'.
This patch also adds a proper test for the pthread guard.
I checked on x86_64, aarch64, powerpc64le, and hppa with kernel 6.13.0-rc7.
Reviewed-by: DJ Delorie <dj@redhat.com>
This request the page to be never written out to swap, it will be zeroed
under memory pressure (so kernel can just drop the page), it is inherited
by fork, it is not counted against @code{mlock} budget, and if there is
no enough memory to service a page faults there is no fatal error (so not
signal is sent).
Tested with build-many-glibcs.py.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
A desired hugetlb page size can be encoded in the flags parameter of
system calls such as mmap() and shmget(). The Linux UAPI headers have
included explicit definitions for these encodings since v4.14.
This patch adds these definitions that are used along with MAP_HUGETLB
and SHM_HUGETLB flags as specified in the corresponding man pages. This
relieves programs from having to duplicate and/or compute the encodings
manually.
Additionally, the filter on these definitions in tst-mman-consts.py is
removed, as suggested by Florian. I then ran this tests successfully,
confirming the alignment with the kernel headers.
PASS: misc/tst-mman-consts
original exit status 0
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Tested-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Linux 5.18 adds a constant MADV_DONTNEED_LOCKED (defined in multiple
header files, but with the same value on all architectures). Add this
constant to bits/mman-linux.h.
Tested for x86_64.
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.
I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah. I don't
know why I run into these diagnostics whereas others evidently do not.
remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
Linux 5.14 adds constants MADV_POPULATE_READ and MADV_POPULATE_WRITE
(with the same values on all architectures). Add these to glibc's
bits/mman-linux.h.
Tested for x86_64.
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
Linux 5.4 adds constants MADV_COLD and MADV_PAGEOUT (defined with the
same values on all architectures). This patch adds them to
bits/mman-linux.h.
Tested for x86_64.
The MREMAP_* flags are identical between bits/mman-linux.h and the
hppa bits/mman.h; thus, they should be in bits/mman-shared.h instead
to avoid unnecessary duplication. This patch moves them there.
Tested for x86_64, and with build-many-glibcs.py.
* sysdeps/unix/sysv/linux/bits/mman-linux.h [__USE_GNU]
(MREMAP_MAYMOVE): Do not define here.
[__USE_GNU] (MREMAP_FIXED): Likewise.
* sysdeps/unix/sysv/linux/bits/mman-shared.h [__USE_GNU]
(MREMAP_MAYMOVE): Define here instead.
[__USE_GNU] (MREMAP_FIXED): Likewise.
* sysdeps/unix/sysv/linux/hppa/bits/mman.h [__USE_GNU]
(MREMAP_MAYMOVE): Remove.
[__USE_GNU] (MREMAP_FIXED): Likewise.
This patch adds the MAP_SHARED_VALIDATE macro from Linux 4.15 to
bits/mman-linux.h and the hppa bits/mman.h.
Tested for x86_64.
* sysdeps/unix/sysv/linux/bits/mman-linux.h [__USE_MISC]
(MAP_SHARED_VALIDATE): New macro.
* sysdeps/unix/sysv/linux/hppa/bits/mman.h [__USE_MISC]
(MAP_SHARED_VALIDATE): Likewise.
This header file enables sharing of portable declarations and
definitions across all Linux architectures, including hppa (which does
not use <bits/mman-linux.h>).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The system call is somewhat obscure because it is closely related
to file descriptor sealing. However, it is also the recommended
way to create alias mappings, which is why it has more general use.
No emulation is provided. Except for the name of the
/proc/self/fd links, it would be possible to implement an
approximation using O_TMPFILE and tmpfs, but this does not appear
to be worth the added complexity.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
This patch adds the new MADV_WIPEONFORK and MADV_KEEPONFORK from Linux
4.14 to bits/mman-linux.h (and bits/mman.h in the hppa case). Note
there are further hppa MADV_* changes in 4.14; I plan a separate glibc
patch for those.
Tested for x86_64.
* sysdeps/unix/sysv/linux/bits/mman-linux.h
[__USE_MISC] (MADV_WIPEONFORK): New macro.
[__USE_MISC] (MADV_KEEPONFORK): Likewise.
* sysdeps/unix/sysv/linux/hppa/bits/mman.h
[__USE_MISC] (MADV_WIPEONFORK): Likewise.
[__USE_MISC] (MADV_KEEPONFORK): Likewise.
* sysdeps/unix/sysv/linux/bits/mman-linux.h (MAP_ANONYMOUS):
Allow definition via __MAP_ANONYMOUS.
* sysdeps/unix/sysv/linux/mips/bits/mman.h: Remove all defines
provided by bits/mman-linux.h and include <bits/mman-linux.h>.
(__MAP_ANONYMOUS): Define.
* sysdeps/unix/sysv/linux/s390/bits/mman.h: Include
<bits/mman-linux.h>.
(MCL_CURRENT, MCL_FUTURE): Do not define here, the generic value
is fine.
* sysdeps/unix/sysv/linux/sh/bits/mman.h: Move include of
<bits/mman-linux.h> to end of file.
(MCL_CURRENT, MCL_FUTURE): Do not define here, the generic value
is fine.
* sysdeps/unix/sysv/linux/x86/bits/mman.h: Move include of
<bits/mman-linux.h> to end of file.
(MCL_CURRENT, MCL_FUTURE): Do not define here, the generic value
is fine.
* sysdeps/unix/sysv/linux/sparc/bits/mman.h: Move include of
<bits/mman-linux.h> to end of file.
* sysdeps/unix/sysv/linux/bits/mman-linux.h [!MCL_CURRENT]
(MCL_CURRENT, MCL_FUTURE): Define here.
* sysdeps/unix/sysv/linux/bits/mman-linux.h: New file, with
Linux common definitions.
* sysdeps/unix/sysv/linux/sh/bits/mman.h: Remove all defines
provided by bits/mman-linux.h and include <bits/mman-linux.h>.
* sysdeps/unix/sysv/linux/x86/bits/mman.h: Likewise.
* sysdeps/unix/sysv/linux/s390/bits/mman.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/bits/mman.h: Likewise.
* sysdeps/unix/sysv/linux/sh/bits/mman.h: Likewise.
* sysdeps/unix/sysv/linux/sparc/bits/mman.h: Likewise.
