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

Christophe Leroy
2024-08-22T07:13:30Z

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

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2.44.0