[PATCH v4 0/5] Wire up getrandom() vDSO implementation on powerpc

Christophe Leroy
2024-09-02T12:04:47Z

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

Tested on PPC32 on real hardware.
Tested on PPC64 (both BE and LE) on QEMU:

Performance on powerpc 885:
~# ./vdso_test_getrandom bench-single
vdso: 25000000 times in 62.938002291 seconds
libc: 25000000 times in 535.581916866 seconds
syscall: 25000000 times in 531.525042806 seconds

Performance on powerpc 8321:
~# ./vdso_test_getrandom bench-single
vdso: 25000000 times in 16.899318858 seconds
libc: 25000000 times in 131.050596522 seconds
syscall: 25000000 times in 129.794790389 seconds

Performance on QEMU pseries:
~ # ./vdso_test_getrandom bench-single
vdso: 25000000 times in 4.977777162 seconds
libc: 25000000 times in 75.516749981 seconds
syscall: 25000000 times in 86.842242014 seconds

Changes in v4:
- Rebased on recent random git tree (963233ff0133) (The new tree includes selftests fixes)
- Read/write counter in native byte order
- Don't use anymore compat macros to write output
- Fixed selftests build failure with patch 4 (without patch 5) on little endian on PPC64
- Implement a __kernel_getrandom() stub returning ENOSYS on ppc64 in patch 4 (without patch 5) to make selftests happy.

Changes in v3:
- Rebased on recent random git tree (0c7e00e22c21)
- Fixed build failures reported by robots around VM_DROPPABLE
- Fixed crash on PPC64 due to clobbered r13 by not using r13 anymore (saving it was not enough for signals).
- Split final patch in two, first for PPC32, second for PPC64
- Moved selftest fixes out of this series

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 (5):
mm: Define VM_DROPPABLE for powerpc/32
powerpc/vdso32: Add crtsavres
powerpc/vdso: Refactor CFLAGS for CVDSO build
powerpc/vdso: Wire up getrandom() vDSO implementation on PPC32
powerpc/vdso: Wire up getrandom() vDSO implementation on PPC64

arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/mman.h | 2 +-
arch/powerpc/include/asm/vdso/getrandom.h | 54 ++++
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 | 57 ++--
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 | 320 +++++++++++++++++++
arch/powerpc/kernel/vdso/vgetrandom.c | 14 +
fs/proc/task_mmu.c | 4 +-
include/linux/mm.h | 4 +-
include/trace/events/mmflags.h | 4 +-
tools/testing/selftests/vDSO/Makefile | 2 +-
17 files changed, 501 insertions(+), 43 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

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2.44.0