[PATCH v2] ld.so.8: Document effect of hwcaps on search path

Jonathan Nieder
2012-04-16T19:03:46Z

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:

> IIUC, your purpose is to allow Debian to drop downstream ld.so.8, by
> ensuring that upstream ld.so.8 has everything that useful from the
> downstream (purpose 1).

Let's just handle them as isolated patches. This one comes from
Debian and the text matches what I get with "man ld.so" on a Debian
system. Since v1, I have rebased it against "master" and rewrapped to
use 76-character instead of 80-character lines.

man8/ld.so.8 | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)

diff --git a/man8/ld.so.8 b/man8/ld.so.8
index 2fbacae0..c0084376 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 capabilities directories (see below)
+are preferred to other libraries.
.IP o
In the default path
.IR /lib ,
@@ -129,6 +131,37 @@ is set-user-ID or set-group-ID.
.TP
.B \-\-audit LIST
Use objects named in LIST as auditors.
+.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
--
1.7.10