[PATCH v3] ld.so.8: Document effect of hwcaps on search path

[Jonathan Nieder <jrnieder-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Wording by Aurelien Jarno from Debian glibc's r4701 (2011-06-04).

Addresses http://bugs.debian.org/622385

Requested-by: Reuben Thomas <rrt-0NV8xZLkR+A@public.gmane.org>
Signed-off-by: Jonathan Nieder <jrnieder-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
Michael Kerrisk (man-pages) wrote:

> Some minor formatting points:
> * Please start new sentences on new lines.
[and other useful feedback about the grammar and substance]

Here goes.

 man8/ld.so.8 |   36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/man8/ld.so.8 b/man8/ld.so.8
index 2fbacae0..72e69f74 100644
--- a/man8/ld.so.8
+++ b/man8/ld.so.8
@@ -64,6 +64,8 @@ in the augmented library path.
 If, however, the binary was linked with the
 .B \-z nodeflib
 linker option, libraries in the default library paths are skipped.
+Libraries installed in hardware capability directories (see below)
+are preferred to other libraries.
 .IP o
 In the default path
 .IR /lib ,
@@ -129,6 +131,40 @@ is set-user-ID or set-group-ID.
 .TP
 .B \-\-audit LIST
 Use objects named in LIST as auditors.
+.SH HARDWARE CAPABILITIES
+Some libraries are compiled using hardware-specific instructions which do
+not exist on every CPU.
+Such libraries should be installed in directories whose names define the
+required hardware capabilities, such as
+.IR /usr/lib/sse2/ .
+The dynamic linker checks these directories against the hardware of the
+machine and selects the most suitable version of a given library.
+Hardware capability directories can be cascaded to combine CPU features.
+The list of supported hardware capability names depends on the CPU.
+The following names are currently recognized:
+.TP
+.B Alpha
+ev4, ev5, ev56, ev6, ev67
+.TP
+.B MIPS
+loongson2e, loongson2f, octeon, octeon2
+.TP
+.B PowerPC
+4xxmac, altivec, arch_2_05, arch_2_06, booke, cellbe, dfp, efpdouble, efpsingle,
+fpu, ic_snoop, mmu, notb, pa6t, power4, power5, power5+, power6x, ppc32, ppc601,
+ppc64, smt, spe, ucache, vsx
+.TP
+.B SPARC
+flush, muldiv, stbar, swap, ultra3, v9, v9v, v9v2
+.TP
+.B s390
+dfp, eimm, esan3, etf3enh, g5, highgprs, hpage, ldisp, msa, stfle,
+z900, z990, z9-109, z10, zarch
+.TP
+.TP
+.B x86 (32-bit only)
+acpi, apic, clflush, cmov, cx8, dts, fxsr, ht, i386, i486, i586, i686, mca, mmx,
+mtrr, pat, pbe, pge, pn, pse36, sep, ss, sse, sse2, tm
 .SH ENVIRONMENT
 There are four important environment variables.
 .TP
-- 
1.7.10

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