[PATCH 6/6] ld.so.8: document how hwcaps affect search path

Jonathan Nieder
2011-10-20T07:16:35Z

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

Fixes 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>
---
I think this information belongs in the ldconfig(8) page, not
ld.so(8), but either one is better than nowhere. ;-)

That's the end of the series. Thanks for reading.

man8/ld.so.8 | 32 ++++++++++++++++++++++++++++++++
1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/man8/ld.so.8 b/man8/ld.so.8
index 409876d..13b5508 100644
--- a/man8/ld.so.8
+++ b/man8/ld.so.8
@@ -63,6 +63,8 @@ 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 capabilities directories (see below)
+are preferred to other libraries.
.IP o
In the default path
.IR /lib ,
@@ -152,6 +154,36 @@ the system libraries directory, which is /lib for the native architecture
on FHS compliant GNU/Linux systems.
.\" ld.so lets names be abbreviated, so $O will work for $ORIGIN;
.\" Don't do this!!
+.SH HARDWARE CAPABILITIES
+Libraries might be compiled using hardware-specific instructions which do not
+exist on every CPU. Such libraries should be installed in directories whose name
+defines the hardware capabilities such as \fB/usr/lib/sse2/\fR. The dynamic
+linker checks these directories against the hardware of the machine and selects
+the best suitable version of a given library. Hardware capabilities directories
+could be cascaded to combine CPU features. Hardware capabilities depends on
+the CPU. The following names are currently recognized:
+.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
--
1.7.7