[v3,0/7] Add a tunable to decorate anonymous memory maps

  Linux 4.5 removed thread stack annotations due to the complexity of
computing them, and Linux 5.17 added support to naming anonymous virtual
memory areas through the prctl syscall [1].

Android and other projects like sanitizers uses this feature to improve
debugability and a way to user understand better what kind of memory
runtime allocates.

The patchset adds annotations for the pthread stack, on both glibc
created and user-provided, on loader minimal malloc and on malloc arenas
and default allocation. For instance, on x86_64 the resulting mapping of
the newly tst-decorate-maps shows:

5649d25bd000-5649d25bf000 r--p 00000000 103:05 40141614                  <buildir>/elf/tst-decorate-maps
5649d25bf000-5649d25c3000 r-xp 00002000 103:05 40141614                  <buildir>/elf/tst-decorate-maps
5649d25c3000-5649d25c5000 r--p 00006000 103:05 40141614                  <buildir>/elf/tst-decorate-maps
5649d25c5000-5649d25c6000 r--p 00007000 103:05 40141614                  <buildir>/elf/tst-decorate-maps
5649d25c6000-5649d25c7000 rw-p 00008000 103:05 40141614                  <buildir>/elf/tst-decorate-maps
5649d36c4000-5649d36e5000 rw-p 00000000 00:00 0                          [heap]
7fc76c000000-7fc76c021000 rw-p 00000000 00:00 0                          [anon: glibc: malloc arena]
7fc76c021000-7fc770000000 ---p 00000000 00:00 0
7fc774000000-7fc774021000 rw-p 00000000 00:00 0                          [anon: glibc: malloc arena]
7fc774021000-7fc778000000 ---p 00000000 00:00 0
7fc77c000000-7fc77c021000 rw-p 00000000 00:00 0                          [anon: glibc: malloc arena]
7fc77c021000-7fc780000000 ---p 00000000 00:00 0
7fc784000000-7fc784021000 rw-p 00000000 00:00 0                          [anon: glibc: malloc arena]
7fc784021000-7fc788000000 ---p 00000000 00:00 0
7fc788000000-7fc788021000 rw-p 00000000 00:00 0                          [anon: glibc: malloc arena]
7fc788021000-7fc78c000000 ---p 00000000 00:00 0
7fc78c000000-7fc78c021000 rw-p 00000000 00:00 0                          [anon: glibc: malloc arena]
7fc78c021000-7fc790000000 ---p 00000000 00:00 0
7fc790000000-7fc790021000 rw-p 00000000 00:00 0                          [anon: glibc: malloc arena]
7fc790021000-7fc794000000 ---p 00000000 00:00 0
7fc796800000-7fc797000000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188506]
7fc797000000-7fc797800000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188505]
7fc797800000-7fc798000000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188504]
7fc798000000-7fc798800000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188503]
7fc798800000-7fc799000000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188502]
7fc799000000-7fc799800000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188501]
7fc799800000-7fc79a000000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188500]
7fc79a000000-7fc79a800000 rw-p 00000000 00:00 0                          [anon: glibc: pthread stack: 2188499]
7fc79a800000-7fc79a826000 r--p 00000000 103:05 38343761                  <buildir>/libc.so
7fc79a826000-7fc79a99a000 r-xp 00026000 103:05 38343761                  <buildir>/libc.so
7fc79a99a000-7fc79a9f1000 r--p 0019a000 103:05 38343761                  <buildir>/libc.so
7fc79a9f1000-7fc79a9f5000 r--p 001f0000 103:05 38343761                  <buildir>/libc.so
7fc79a9f5000-7fc79a9f7000 rw-p 001f4000 103:05 38343761                  <buildir>/libc.so
7fc79a9f7000-7fc79aa04000 rw-p 00000000 00:00 0
7fc79aabb000-7fc79aafb000 rw-p 00000000 00:00 0                          [anon: glibc: pthread user stack: 2188508]
7fc79aafb000-7fc79ab3b000 rw-p 00000000 00:00 0                          [anon: glibc: pthread user stack: 2188507]
7fc79ab3b000-7fc79ab7c000 rw-p 00000000 00:00 0                          [anon: glibc: malloc]
7fc79ab7c000-7fc79ab7d000 rw-s 00000000 00:01 19458                      /dev/zero (deleted)
7fc79ab7d000-7fc79ab82000 rw-p 00000000 00:00 0                          [anon: glibc: loader malloc]
7fc79ab82000-7fc79ab83000 r--p 00000000 103:05 40141609                  <buildir>/elf/ld.so
7fc79ab83000-7fc79aba9000 r-xp 00001000 103:05 40141609                  <buildir>/elf/ld.so
7fc79aba9000-7fc79abb3000 r--p 00027000 103:05 40141609                  <buildir>/elf/ld.so
7fc79abb3000-7fc79abb5000 r--p 00031000 103:05 40141609                  <buildir>/elf/ld.so
7fc79abb5000-7fc79abb7000 rw-p 00033000 103:05 40141609                  <buildir>/elf/ld.so
7ffdb2f1d000-7ffdb2f3f000 rw-p 00000000 00:00 0                          [stack]
7ffdb2f7a000-7ffdb2f7e000 r--p 00000000 00:00 0                          [vvar]
7ffdb2f7e000-7ffdb2f80000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0                  [vsyscall]

The PR_SET_VMA_ANON_NAME support is currently only enabled through a
configurable kernel switch, mainly because assigning a name to a
anonymous virtual memory area might prevent that area from being
merged with adjacent virtual memory areas. There is also a potential
scalability issue, where the prctl requires take the mmap global lock
and it still not fully fixed in Linux [1] (for pthread stacks and
arenas, it is mitigated by the stack cached and the arena reuse).

So the decoration is only enable through a new tunable,
glibc.mem.decorate_maps.

[1] https://github.com/torvalds/linux/commit/65376df582174ffcec9e6471bf5b0dd79ba05e4a
[1] https://github.com/torvalds/linux/commit/9a10064f5625d5572c3626c1516e0bebc6c9fe9b

Changes from v2:
* Rename support_set_vma_name to support_set_vma_name_supported.
* Extend documentation.

Changes from v1:
* Fixed arm thumb build.
* Added decoration on assert and __libc_fatal.

Adhemerval Zanella (7):
  linux: Add PR_SET_VMA_ANON_NAME support
  support: Add support_set_vma_name
  nptl: Decorate thread stack on pthread_create
  malloc: Decorate malloc maps
  assert: Decorate error message buffer
  linux: Decorate __libc_fatal error buffer
  elf: Add glibc.mem.decorate_maps tunable

 NEWS                                     |   5 +
 assert/assert.c                          |   2 +
 elf/Makefile                             |   7 +
 elf/dl-minimal-malloc.c                  |   2 +
 elf/dl-tunables.list                     |   5 +
 elf/tst-decorate-maps.c                  | 196 +++++++++++++++++++++++
 include/sys/prctl.h                      |   5 +
 malloc/arena.c                           |   4 +
 malloc/malloc.c                          |   5 +
 manual/tunables.texi                     |  17 ++
 nptl/Makefile                            |   4 +
 nptl/allocatestack.c                     |  40 +++++
 nptl/pthread_create.c                    |   6 +
 support/Makefile                         |   1 +
 support/support.h                        |   4 +
 support/support_set_vma_name_supported.c |  49 ++++++
 sysdeps/generic/setvmaname.h             |  27 ++++
 sysdeps/posix/libc_fatal.c               |   3 +
 sysdeps/unix/sysv/linux/Makefile         |   1 +
 sysdeps/unix/sysv/linux/setvmaname.c     |  49 ++++++
 sysdeps/unix/sysv/linux/setvmaname.h     |  36 +++++
 21 files changed, 468 insertions(+)
 create mode 100644 elf/tst-decorate-maps.c
 create mode 100644 support/support_set_vma_name_supported.c
 create mode 100644 sysdeps/generic/setvmaname.h
 create mode 100644 sysdeps/unix/sysv/linux/setvmaname.c
 create mode 100644 sysdeps/unix/sysv/linux/setvmaname.h