On 11/03/2011 09:34 PM, Jon Masters wrote:
Panu Matilainen<pmati...@laiskiainen.org> wrote:
On 10/21/2011 10:20 PM, Dennis Gilmore wrote:
long term maybe we can do something better. right now im looking for
a
way to enable yum to detect the arches correctly without it resorting
to things like running readelf to determine the abi of the running
system. since its noarch we cant just patch things in conditionally.
BTW I was under the impression the ABI information for hard vs softfp
simply DOES NOT EXIST in the ELF headers (or anywhere else for that
matter). If
http://wiki.debian.org/ArmHardFloatPort/VfpComparison#ld.so_hwcaps is
wrong (or I'm misreading it) and you know of a way to detect it
afterall, do let me know.
- Panu -
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It is in an optional section we do carry - see readelf -A. At an ARM conference
so will discuss with Steve McIntyre of ARM (who is driving this ABI on their
end).
Okay, in that case there's hope. Looking at what I hope to be a suitable
sample specimen:
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "7-A"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_FP_arch: VFPv3-D16
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: int
Tag_ABI_HardFP_use: SP and DP
Tag_ABI_VFP_args: VFP registers
Tag_DIV_use: Not allowed
...the interesting part would be Tag_ABI_VFP_args, or...?
Would that happen to be available at runtime through the auxiliary
vector (hwcap or wherever)?
At buildtime, one (easy, since this IS recorded in the ELF headers)
possibility is making elfdeps generate different looking dependencies
when the VFP flag is present, eg something like "libfoo.1.so" vs
"libfoo.1.so()(vfp)", so packages for the other ABI wont satisfy
dependencies of the other one, despite both being technically compatible
architecture-wise (on a system capable of using VFP ABI)
- Panu -
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