rtld-elf: Pass HWCAP flags to ifunc resolver functions

[sarah.walker2_arm.com]

Summary

Function arguments are based on Section 9.4.1 "GNU C Library IFUNC interface"
from "System V ABI for the Arm 64-bit Architecture (AArch64)", 2025Q1.
(https://github.com/ARM-software/abi-aa/releases/download/2025Q1/sysvabi64.pdf)

Sponsored by: Arm Ltd

[andrew]

There should be a followup change to sys/arm64/include/ifunc.h to update DEFINE_UIFUNC. We can also use this to simplify the ifunc handlers in sys/crypto/sha2/sha512c.c and sys/crypto/sha2/sha256c.c

[jrtc27]

Will you also be implementing this for csu for static binaries (often forgotten, including by me in the past)?

libexec/rtld-elf/aarch64/reloc.c

448

Why isn't this in a header?

454

Can this be NULL?

libexec/rtld-elf/aarch64/rtld_machdep.h

78

Shouldn't this live in a header somewhere? The SysV document also says glibc provides an __ifunc_arg_t typedef if you want to be fully compatible.

79–83

They're only uint64_t as placeholders for passing a 0 in a register.

[sarah.walker2_arm.com]

In D54559#1246501, @andrew wrote:

There should be a followup change to sys/arm64/include/ifunc.h to update DEFINE_UIFUNC. We can also use this to simplify the ifunc handlers in sys/crypto/sha2/sha512c.c and sys/crypto/sha2/sha256c.c

Can you give more detail on what you want here please?

[andrew]

In D54559#1246536, @sarah.walker2_arm.com wrote:

In D54559#1246501, @andrew wrote:

There should be a followup change to sys/arm64/include/ifunc.h to update DEFINE_UIFUNC. We can also use this to simplify the ifunc handlers in sys/crypto/sha2/sha512c.c and sys/crypto/sha2/sha256c.c

Can you give more detail on what you want here please?

ifunc.h has the DEFINE_UIFUNC macro where the first two arguments in the generated function signature will need an update. The other two files use DEFINE_UIFUNC and call elf_aux_info to read the HWCAPs, but could be updated after this change (and a similar change for static binaries)

[sarah.walker2_arm.com]

Address review comments.

[sarah.walker2_arm.com]

In D54559#1246537, @andrew wrote:

In D54559#1246536, @sarah.walker2_arm.com wrote:

In D54559#1246501, @andrew wrote:

There should be a followup change to sys/arm64/include/ifunc.h to update DEFINE_UIFUNC. We can also use this to simplify the ifunc handlers in sys/crypto/sha2/sha512c.c and sys/crypto/sha2/sha256c.c

Can you give more detail on what you want here please?

ifunc.h has the DEFINE_UIFUNC macro where the first two arguments in the generated function signature will need an update. The other two files use DEFINE_UIFUNC and call elf_aux_info to read the HWCAPs, but could be updated after this change (and a similar change for static binaries)

Addressed in https://reviews.freebsd.org/D54598 and https://reviews.freebsd.org/D54600

libexec/rtld-elf/aarch64/reloc.c

448

Moved to header - see https://reviews.freebsd.org/D54598

libexec/rtld-elf/aarch64/rtld_machdep.h

78

See https://reviews.freebsd.org/D54598

[kib]

libexec/rtld-elf/aarch64/reloc.c

454–461

Can this be done statically?

455

[sarah.walker2_arm.com]

Address review comments.

[sarah.walker2_arm.com]

In D54559#1246503, @jrtc27 wrote:

Will you also be implementing this for csu for static binaries (often forgotten, including by me in the past)?

See https://reviews.freebsd.org/D54599

[jrtc27]

libexec/rtld-elf/aarch64/rtld_machdep.h

80–83

Both these lines now exceed 80 chars (I suggest using tools/build/checkstyle9.pl prior to submitting patches)

[jrtc27]

libexec/rtld-elf/aarch64/reloc.c

454–461

Exceeds 80 chars

455

This, and the hwcap3/4 lines, are indented using spaces not tabs

[sarah.walker2_arm.com]

Address style issues.

[kib]

libexec/rtld-elf/aarch64/reloc.c

455

Continuation lines should use indent +4 spaces.

libexec/rtld-elf/aarch64/rtld_machdep.h

83

No need to additionally indent, it is constant +4 spaces relatively to the start of the split line.

[sarah.walker2_arm.com]

Fix indentation issues.

[kib]

libexec/rtld-elf/aarch64/reloc.c

447

As a pure cosmetic, I do not think that we need to put __ifunc_arg into the private namespace. This is rtld, which is freestanding program, and which symbols are exported in controlled way. So there would be no harm from removing the '__' prefix.

[sarah.walker2_arm.com]

Move ifunc_arg from private namespace and fix const-ness.