| Message ID | 1496347928-19432-3-git-send-email-siddhesh@sourceware.org |
|---|---|
| State | New |
| Headers | show |
On 01/06/2017 17:12, 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 remark below. > --- > elf/dl-tunables.list | 7 +++++++ > manual/tunables.texi | 23 +++++++++++++++++++++++ > scripts/gen-tunables.awk | 1 + > 3 files changed, 31 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 > + } > + } LD_HWCAP_MASK is on UNSECURE_ENVVARS at sysdeps/generic/unsecvars.h, so I think we should add a security_level: SXID_IGNORE for hwcap_mask as well.
On 06/06/2017 14:57, Adhemerval Zanella wrote: > > > On 01/06/2017 17:12, 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 remark below. > >> --- >> elf/dl-tunables.list | 7 +++++++ >> manual/tunables.texi | 23 +++++++++++++++++++++++ >> scripts/gen-tunables.awk | 1 + >> 3 files changed, 31 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 >> + } >> + } > > LD_HWCAP_MASK is on UNSECURE_ENVVARS at sysdeps/generic/unsecvars.h, so I think > we should add a security_level: SXID_IGNORE for hwcap_mask as well. > I am getting build errors for i686 and s390{x} with --enable-tunables: In file included from /home/azanella/Projects/glibc/build/i686-linux-gnu/dl-tunable-list.h:6:0, from ./dl-tunables.h:67, from ../elf/dl-sysdep.c:47, from ../sysdeps/unix/sysv/linux/dl-sysdep.c:38: ../sysdeps/unix/sysv/linux/i386/dl-procinfo.h:25:1: error: redefinition of ‘_dl_procinfo’ _dl_procinfo (unsigned int type, unsigned long int word) ^~~~~~~~~~~~ In file included from ../elf/dl-sysdep.c:42:0, from ../sysdeps/unix/sysv/linux/dl-sysdep.c:38: ../sysdeps/unix/sysv/linux/i386/dl-procinfo.h:25:1: note: previous definition of ‘_dl_procinfo’ was here _dl_procinfo (unsigned int type, unsigned long int word) ^~~~~~~~~~~~ It because both Linux i686 and s390 dl-procinfo.h do not have include guard (as for the other dl-procinfo.h implementation). I think you should include them on this patch.
On Tuesday 06 June 2017 11:27 PM, Adhemerval Zanella wrote: > LD_HWCAP_MASK is on UNSECURE_ENVVARS at sysdeps/generic/unsecvars.h, so I think > we should add a security_level: SXID_IGNORE for hwcap_mask as well. It is in UNSECURE_ENVVARS, so it should be SXID_ERASE (the default) and not SXID_IGNORE since the latter will make the tunable available for children of setuid processes. Siddhesh
On 07/06/2017 02:33, Siddhesh Poyarekar wrote: > On Tuesday 06 June 2017 11:27 PM, Adhemerval Zanella wrote: >> LD_HWCAP_MASK is on UNSECURE_ENVVARS at sysdeps/generic/unsecvars.h, so I think >> we should add a security_level: SXID_IGNORE for hwcap_mask as well. > > It is in UNSECURE_ENVVARS, so it should be SXID_ERASE (the default) and > not SXID_IGNORE since the latter will make the tunable available for > children of setuid processes. Right, I wasn't aware SXID_ERASE was the default. Thanks for the clarification.
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..c9a4cb7 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 +192,24 @@ 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. +@end deftp 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"