Since arm64 has now used all of AT_HWCAP2 it needs to either start using AT_HWCAP3 (which was recently added for PowerPC) or start allocating bits 32..61 of AT_HWCAP first. Those are documented in elf_hwcaps.rst as unused and in uapi/asm/hwcap.h as unallocated for potential use by libc, glibc does currently use bits 62 and 63. This series has the code for enabling AT_HWCAP3 as a reference. While we've decided to go with using the high bits of AT_HWCAP for now we will exhaust those at some point so it seems helpful to have this code available in order to make life easier when we do need to start using AT_HWCAP3. This seems like it might come up relatively quickly, for the past few years the dpISA has used ~15 hwcaps due to the fine grained feature definitions and the fact that SVE and SME need independent definitions of everything. When we do start using HWCAP3 we'll potentially have multiple serieses that need to share the addition so it seems like it might be helpful to have the scaffolding in place at least the release before it's actuallly required in order to make things more managable. That's not an issue *now* but could come up surprisingly quickly. Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> --- Changes in v2: - Rebase onto v6.12-rc1. - Fix cut'n'paste 3/4 issues. - Link to v1: https://lore.kernel.org/r/20240906-arm64-elf-hwcap3-v1-0-8df1a5e63508@xxxxxxxxxx --- Mark Brown (2): binfmt_elf: Wire up AT_HWCAP3 at AT_HWCAP4 arm64: Support AT_HWCAP3 Documentation/arch/arm64/elf_hwcaps.rst | 6 +++--- arch/arm64/include/asm/cpufeature.h | 3 ++- arch/arm64/include/asm/hwcap.h | 6 +++++- arch/arm64/include/uapi/asm/hwcap.h | 4 ++++ arch/arm64/kernel/cpufeature.c | 6 ++++++ fs/binfmt_elf.c | 6 ++++++ fs/binfmt_elf_fdpic.c | 6 ++++++ fs/compat_binfmt_elf.c | 10 ++++++++++ 8 files changed, 42 insertions(+), 5 deletions(-) --- base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc change-id: 20240905-arm64-elf-hwcap3-7709c5593d34 Best regards, -- Mark Brown <broonie@xxxxxxxxxx>
