Subject: [PATCH v2 00/17] Wire up getrandom() vDSO implementation on powerpc

From: Christophe Leroy <[email-masked]>
Date: Thu, 22 Aug 2024 09:13:08 +0200

This series wires up getrandom() vDSO implementation on powerpc.

Tested on PPC32.

Performance on powerpc 885 (using kernel selftest):
	~# ./vdso_test_getrandom bench-single
	   vdso: 2500000 times in 7.897495392 seconds
	   libc: 2500000 times in 56.091632232 seconds
	syscall: 2500000 times in 55.704851989 seconds

Performance on powerpc 8321 (using kernel selftest):
	~# ./vdso_test_getrandom bench-single
	   vdso: 2500000 times in 2.017183250 seconds
	   libc: 2500000 times in 13.088533630 seconds
	syscall: 2500000 times in 12.952458068 seconds

Only build tested on PPC64. There is a problem with vdso_test_getrandom
selftest, it doesn't find vDSO symbol __kernel_getrandom. There is the
same problem with vdso_test_gettimeofday so it is not related to
getrandom.

On strange things to be clarified, there is the format of the key passed
to __arch_chacha20_blocks_nostack(). In struct vgetrandom_state it is
declared as a table of u32, but in reality it seems it is a flat storage
that needs to be loaded in reversed byte order, so it should either be
defined as a table of bytes, or as a table of __le32 but not a table of
u32. But this has no impact and can be clarified later and fixed in a
follow-up patch.

Changes in v2:
- Define VM_DROPPABLE for powerpc/32
- Fixes generic vDSO getrandom headers to enable CONFIG_COMPAT build.
- Fixed size of generation counter
- Fixed selftests to work on non x86 architectures

Christophe Leroy (17):
  asm-generic/unaligned.h: Extract common header for vDSO
  vdso: Clean header inclusion in getrandom
  vdso: Add __arch_get_k_vdso_rng_data()
  vdso: Add missing c-getrandom-y in Makefile
  vdso: Avoid call to memset() by getrandom
  vdso: Change getrandom's generation to unsigned long
  mm: Define VM_DROPPABLE for powerpc/32
  powerpc: Add little endian variants of LWZX_BE and STWX_BE
  powerpc/vdso32: Add crtsavres
  powerpc/vdso: Refactor CFLAGS for CVDSO build
  powerpc/vdso: Wire up getrandom() vDSO implementation
  selftests: vdso: Fix powerpc64 vdso_config
  selftests: vdso: Don't hard-code location of vDSO sources
  selftests: vdso: Make test_vdso_getrandom look for the right vDSO
    function
  selftests: vdso: Fix build of test_vdso_chacha
  selftests: vdso: Make VDSO function call more generic
  selftests: vdso: Add support for vdso_test_random for powerpc

 arch/powerpc/Kconfig                          |   1 +
 arch/powerpc/include/asm/asm-compat.h         |   8 +
 arch/powerpc/include/asm/mman.h               |   2 +-
 arch/powerpc/include/asm/vdso/getrandom.h     |  67 ++++
 arch/powerpc/include/asm/vdso/vsyscall.h      |   6 +
 arch/powerpc/include/asm/vdso_datapage.h      |   2 +
 arch/powerpc/kernel/asm-offsets.c             |   1 +
 arch/powerpc/kernel/vdso/Makefile             |  45 ++-
 arch/powerpc/kernel/vdso/getrandom.S          |  58 ++++
 arch/powerpc/kernel/vdso/gettimeofday.S       |  13 -
 arch/powerpc/kernel/vdso/vdso32.lds.S         |   1 +
 arch/powerpc/kernel/vdso/vdso64.lds.S         |   1 +
 arch/powerpc/kernel/vdso/vgetrandom-chacha.S  | 297 ++++++++++++++++++
 arch/powerpc/kernel/vdso/vgetrandom.c         |  14 +
 arch/x86/entry/vdso/vma.c                     |   3 +
 arch/x86/include/asm/pvclock.h                |   1 +
 arch/x86/include/asm/vdso/vsyscall.h          |  10 +-
 drivers/char/random.c                         |   5 +-
 fs/proc/task_mmu.c                            |   4 +-
 include/asm-generic/unaligned.h               |  11 +-
 include/linux/mm.h                            |   4 +-
 include/trace/events/mmflags.h                |   4 +-
 include/vdso/datapage.h                       |   2 +-
 include/vdso/getrandom.h                      |   2 +-
 include/vdso/helpers.h                        |   1 +
 include/vdso/unaligned.h                      |  15 +
 lib/vdso/Makefile                             |   1 +
 lib/vdso/getrandom.c                          |  30 +-
 tools/arch/powerpc/vdso                       |   1 +
 tools/arch/x86/vdso                           |   1 +
 tools/include/linux/linkage.h                 |   4 +
 tools/testing/selftests/vDSO/Makefile         |  12 +-
 tools/testing/selftests/vDSO/vdso_call.h      |  52 +++
 tools/testing/selftests/vDSO/vdso_config.h    |  14 +-
 .../selftests/vDSO/vdso_test_getrandom.c      |  11 +-
 35 files changed, 628 insertions(+), 76 deletions(-)
 create mode 100644 arch/powerpc/include/asm/vdso/getrandom.h
 create mode 100644 arch/powerpc/kernel/vdso/getrandom.S
 create mode 100644 arch/powerpc/kernel/vdso/vgetrandom-chacha.S
 create mode 100644 arch/powerpc/kernel/vdso/vgetrandom.c
 create mode 100644 include/vdso/unaligned.h
 create mode 120000 tools/arch/powerpc/vdso
 create mode 120000 tools/arch/x86/vdso
 create mode 100644 tools/testing/selftests/vDSO/vdso_call.h

-- 
2.44.0