Do not export AT_CLKTCK when emulating Linux kernel prior

to 2.4.0, as it has appeared in the 2.4.0-rc7 first time.
Being exported, AT_CLKTCK is returned by sysconf(_SC_CLK_TCK),
glibc falls back to the hard-coded CLK_TCK value when aux entry
is not present.

Glibc versions prior to 2.2.1 always use hard-coded CLK_TCK value.

For older applications/libc's which depends on hard-coded CLK_TCK
value user should set compat.linux.osrelease less than 2.4.0.

Approved by:	kib (mentor)

2 files changed, 14 insertions, 1 deletions

diff --git a/sys/compat/linux/linux_mib.h b/sys/compat/linux/linux_mib.h
index 9f0f41c..f78a5e5 100644
--- a/sys/compat/linux/linux_mib.h
+++ b/sys/compat/linux/linux_mib.h
@@ -45,6 +45,7 @@ int	linux_set_oss_version(struct thread *td, int oss_version);
 
 int	linux_kernver(struct thread *td);
 
+#define	LINUX_KERNVER_2004000		2004000
 #define	LINUX_KERNVER_2006000		2006000
 
 #define	linux_use26(t)		(linux_kernver(t) >= LINUX_KERNVER_2006000)
diff --git a/sys/compat/linux/linux_misc.c b/sys/compat/linux/linux_misc.c
index c5b1e54..7279197 100644
--- a/sys/compat/linux/linux_misc.c
+++ b/sys/compat/linux/linux_misc.c
@@ -661,7 +661,19 @@ struct l_times_argv {
 	l_clock_t	tms_cstime;
 };
 
-#define CONVTCK(r)	(r.tv_sec * stclohz + r.tv_usec / (1000000 / stclohz))
+
+/*
+ * Glibc versions prior to 2.2.1 always use hard-coded CLK_TCK value.
+ * Since 2.2.1 Glibc uses value exported from kernel via AT_CLKTCK
+ * auxiliary vector entry.
+ */
+#define	CLK_TCK		100
+
+#define	CONVOTCK(r)	(r.tv_sec * CLK_TCK + r.tv_usec / (1000000 / CLK_TCK))
+#define	CONVNTCK(r)	(r.tv_sec * stclohz + r.tv_usec / (1000000 / stclohz))
+
+#define	CONVTCK(r)	(linux_kernver(td) >= LINUX_KERNVER_2004000 ?		\
+			    CONVNTCK(r) : CONVOTCK(r))
 
 int
 linux_times(struct thread *td, struct linux_times_args *args)