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getauxval.3: Correct AT_HWCAP result description 

The getauxval(3) man page describes the result for AT_HWCAP as
"A pointer to a multibyte mask of bits", however the actual value
returned is not a pointer, but simply the first 32 bits of the
capabilities mask.

This can be observed directly. Note the value shown for AT_HWCAP
is a 32 bit value that is not a pointer (see AT_PHDR or AT_RANDOM
for how pointers are shown).

% LD_SHOW_AUXV=1 cat < /dev/null
AT_SYSINFO_EHDR: 0x7fffe89fe000
AT_HWCAP:        bfebfbff
AT_PAGESZ:       4096
AT_CLKTCK:       100
AT_PHDR:         0x400040
AT_PHENT:        56
AT_PHNUM:        9
AT_BASE:         0x0
AT_FLAGS:        0x0
AT_ENTRY:        0x402634
AT_UID:          515
AT_EUID:         515
AT_GID:          114
AT_EGID:         114
AT_SECURE:       0
AT_RANDOM:       0x7fffe8917be9
AT_EXECFN:       /usr/bin/cat
AT_PLATFORM:     x86_64
This commit is contained in:
Cownie, James H 2016-07-12 16:35:43 +00:00 committed by Michael Kerrisk
parent 8c74a1cea4
commit 063bf5a777
1 changed files with 3 additions and 2 deletions
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@ -101,12 +101,13 @@ performed by the kernel.
The real group ID of the thread. The real group ID of the thread.
.TP .TP
.BR AT_HWCAP .BR AT_HWCAP
A pointer to a multibyte mask of bits whose settings A four byte long bit-mask whose settings
indicate detailed processor capabilities. indicate detailed processor capabilities.
The contents of the bit mask are hardware dependent The contents of the bit mask are hardware dependent
(for example, see the kernel source file (for example, see the kernel source file
.IR arch/x86/include/asm/cpufeature.h .IR arch/x86/include/asm/cpufeature.h
for details relating to the Intel x86 architecture). for details relating to the Intel x86 architecture; the value
returned is the first 32 bit word of the array described there).
A human-readable version of the same information is available via A human-readable version of the same information is available via
.IR /proc/cpuinfo . .IR /proc/cpuinfo .
.TP .TP