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| author | H.J. Lu <hjl.tools@gmail.com> | 2015-12-16 14:40:40 +0100 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2015-12-16 16:43:44 +0100 |
| commit | 5b479f37b6ed092462a00fe229e32ad25e9542fe (patch) | |
| tree | 0cfefc44259f1ea541fafb16f51bdf13a180e88a /man8 | |
| parent | cc15860198af01fb46038a8e03cd554e3b3973a2 (diff) | |
| download | man-pages-5b479f37b6ed092462a00fe229e32ad25e9542fe.tar.gz | |
ld.so.8: Document LD_PREFER_MAP_32BIT_EXEC
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Diffstat (limited to 'man8')
| -rw-r--r-- | man8/ld.so.8 | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/man8/ld.so.8 b/man8/ld.so.8 index 608cf7c557..da3340499e 100644 --- a/man8/ld.so.8 +++ b/man8/ld.so.8 @@ -472,6 +472,16 @@ environment variable has been set. (ELF only)(glibc since 2.1.3) If set to a nonempty string, warn about unresolved symbols. .TP +.B LD_PREFER_MAP_32BIT_EXEC +(x86-64 only)(glibc since 2.23) +According to Silvermont software optimization guide, for 64-bit +applications, branch prediction performance can be negatively impacted +when the target of a branch is more than 4GB away from the branch. +If set, ld.so will try to map executable pages with MAP_32BIT first. +NB: MAP_32BIT will map to lower 2GB, not lower 4GB, address. Since +MAP_32BIT reduces bits available for address space layout randomization +(ASLR), LD_PREFER_MAP_32BIT_EXEC is always disabled for SUID programs. +.TP .B LDD_ARGV0 (libc5) .IR argv [0] |