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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2021-07-10 17:03:49 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2021-07-12 17:37:56 -0300
commit72e84d1db22203e01a43268de71ea8669eca2863 (patch)
tree45eab8537afcfb66419a29d24a01c83dd9f9cde1 /sysdeps/unix/sysv/linux/Makefile
parentaaacde11f2e814814fdd19dfb683e76f1dede4d5 (diff)
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Linux: Use 32-bit vDSO for clock_gettime, gettimeofday, time (BZ# 28071)
The previous approach defeats the vDSO optimization on older kernels
because a failing clock_gettime64 system call is performed on every
function call.  It also results in a clobbered errno value, exposing
an OpenJDK bug (JDK-8270244).

This patch fixes by open-code INLINE_VSYSCALL macro and replace all
INLINE_SYSCALL_CALL with INTERNAL_SYSCALL_CALLS.  Now for
__clock_gettime64x, the 64-bit vDSO is used and the 32-bit vDSO is
tried before falling back to 64-bit syscalls.

The previous code preferred 64-bit syscall for the case where the kernel
provides 64-bit time_t syscalls *and* also a 32-bit vDSO (in this case
the *64-bit* syscall should be preferable over the vDSO).  All
architectures that provides 32-bit vDSO (i386, mips, powerpc, s390)
modulo sparc; but I am not sure if some kernels versions do provide
only 32-bit vDSO while still providing 64-bit time_t syscall.
Regardless, for such cases the 64-bit time_t syscall is used if the
vDSO returns overflowed 32-bit time_t.

Tested on i686-linux-gnu (with a time64 and non-time64 kernel),
x86_64-linux-gnu.  Built with build-many-glibcs.py.

Co-authored-by: Florian Weimer <fweimer@redhat.com>
Diffstat (limited to 'sysdeps/unix/sysv/linux/Makefile')
-rw-r--r--sysdeps/unix/sysv/linux/Makefile6
1 files changed, 6 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 8257e5b548..feb8fd4ce1 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -213,6 +213,12 @@ ifeq ($(subdir),time)
 sysdep_headers += sys/timex.h bits/timex.h
 
 sysdep_routines += ntp_gettime ntp_gettimex
+
+tests += \
+  tst-clock_gettime-clobber \
+  tst-gettimeofday-clobber \
+  tst-time-clobber \
+  # tests
 endif
 
 ifeq ($(subdir),signal)