| Message ID | 1495138038-32212-3-git-send-email-siddhesh@sourceware.org |
|---|---|
| State | New |
| Headers | show |
On 18/05/2017 17:07, Siddhesh Poyarekar wrote: > Add LD_HWCAP_MASK to tunables in preparation of it being removed from > rtld.c. This allows us to read LD_HWCAP_MASK much earlier so that it > can influence IFUNC resolution in aarch64. > > This patch does not actually do anything other than read the > LD_HWCAP_MASK variable and add the tunables way to set the > LD_HWCAP_MASK, i.e. via the glibc.tune.hwcap_mask tunable. In a > follow-up patch, the _dl_hwcap_mask will be replaced with > glibc.tune.hwcap_mask to complete the transition. > > * elf/dl-tunables.list: Add glibc.tune.hwcap_mask. > * scripts/gen-tunables.awk: Include dl-procinfo.h. > * manual/tunables.texi: Document glibc.tune.hwcap_mask. LGTM with a small fix below. > --- > elf/dl-tunables.list | 7 +++++++ > manual/tunables.texi | 22 ++++++++++++++++++++++ > scripts/gen-tunables.awk | 1 + > 3 files changed, 30 insertions(+) > > diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list > index b9f1488..41ce9af 100644 > --- a/elf/dl-tunables.list > +++ b/elf/dl-tunables.list > @@ -77,4 +77,11 @@ glibc { > security_level: SXID_IGNORE > } > } > + tune { > + hwcap_mask { > + type: UINT_64 > + env_alias: LD_HWCAP_MASK > + default: HWCAP_IMPORTANT > + } > + } > } > diff --git a/manual/tunables.texi b/manual/tunables.texi > index ac8c38f..37aefca 100644 > --- a/manual/tunables.texi > +++ b/manual/tunables.texi > @@ -31,6 +31,8 @@ their own namespace. > @menu > * Tunable names:: The structure of a tunable name > * Memory Allocation Tunables:: Tunables in the memory allocation subsystem > +* Hardware Capability Tunables:: Tunables that modify the hardware > + capabilities seen by @theglibc{} > @end menu > > @node Tunable names > @@ -190,3 +192,23 @@ number of arenas is determined by the number of CPU cores online. For 32-bit > systems the limit is twice the number of cores online and on 64-bit systems, it > is 8 times the number of cores online. > @end deftp > + > +@node Hardware Capability Tunables > +@section Hardware Capability Tunables > +@cindex hardware capability tunables > +@cindex hwcap tunables > +@cindex tunables, hwcap > + > +@deftp {Tunable namespace} glibc.tune > +Behavior of @theglibc{} can be tuned to assume specific hardware capabilities > +by setting the following tunables in the @code{tune} namespace: > +@end deftp > + > +@deftp Tunable glibc.tune.hwcap_mask > +This tunable supersedes the @env{LD_HWCAP_MASK} environment variable and is > +identical in features. > + > +The @code{AT_HWCAP} key in the Auxilliary Vector specifies instruction set > +extensions available in the processor at runtime for some architectures. The > +@code{glibc.tune.hwcap_mask} tunable allows the user to mask out those > +capabilities at runtime, thus disabling use of those extensions. Missing @end deftp here. > diff --git a/scripts/gen-tunables.awk b/scripts/gen-tunables.awk > index b10b00e..93e5aff 100644 > --- a/scripts/gen-tunables.awk > +++ b/scripts/gen-tunables.awk > @@ -134,6 +134,7 @@ END { > print "# error \"Do not include this file directly.\"" > print "# error \"Include tunables.h instead.\"" > print "#endif" > + print "#include <dl-procinfo.h>\n" > > # Now, the enum names > print "\ntypedef enum" >
diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list index b9f1488..41ce9af 100644 --- a/elf/dl-tunables.list +++ b/elf/dl-tunables.list @@ -77,4 +77,11 @@ glibc { security_level: SXID_IGNORE } } + tune { + hwcap_mask { + type: UINT_64 + env_alias: LD_HWCAP_MASK + default: HWCAP_IMPORTANT + } + } } diff --git a/manual/tunables.texi b/manual/tunables.texi index ac8c38f..37aefca 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -31,6 +31,8 @@ their own namespace. @menu * Tunable names:: The structure of a tunable name * Memory Allocation Tunables:: Tunables in the memory allocation subsystem +* Hardware Capability Tunables:: Tunables that modify the hardware + capabilities seen by @theglibc{} @end menu @node Tunable names @@ -190,3 +192,23 @@ number of arenas is determined by the number of CPU cores online. For 32-bit systems the limit is twice the number of cores online and on 64-bit systems, it is 8 times the number of cores online. @end deftp + +@node Hardware Capability Tunables +@section Hardware Capability Tunables +@cindex hardware capability tunables +@cindex hwcap tunables +@cindex tunables, hwcap + +@deftp {Tunable namespace} glibc.tune +Behavior of @theglibc{} can be tuned to assume specific hardware capabilities +by setting the following tunables in the @code{tune} namespace: +@end deftp + +@deftp Tunable glibc.tune.hwcap_mask +This tunable supersedes the @env{LD_HWCAP_MASK} environment variable and is +identical in features. + +The @code{AT_HWCAP} key in the Auxilliary Vector specifies instruction set +extensions available in the processor at runtime for some architectures. The +@code{glibc.tune.hwcap_mask} tunable allows the user to mask out those +capabilities at runtime, thus disabling use of those extensions. diff --git a/scripts/gen-tunables.awk b/scripts/gen-tunables.awk index b10b00e..93e5aff 100644 --- a/scripts/gen-tunables.awk +++ b/scripts/gen-tunables.awk @@ -134,6 +134,7 @@ END { print "# error \"Do not include this file directly.\"" print "# error \"Include tunables.h instead.\"" print "#endif" + print "#include <dl-procinfo.h>\n" # Now, the enum names print "\ntypedef enum"