If PER_LINUX32 is set calling sys_personality, we will try to
find the corresponding exec_domain. This causes us to try to load a
module for personality-8. After running the userspace module loader
and failing to find the module, we fall back to the default.
We can avoid the failed module loading overhead by building-in the
linux32_exec_domain for systems that have CONFIG_COMPAT.
I noticed this on MIPS64 systems, but it is a general problem and
applies to x86 among others. Admittedly sys_personality() is probably
not in the hot path of many programs, but the overhead of the extra
exec_domain is fairly small.
Signed-off-by: David Daney <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Oleg Nesterov <[email protected]>
---
kernel/exec_domain.c | 14 ++++++++++++++
1 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/kernel/exec_domain.c b/kernel/exec_domain.c
index 0dbeae3..9335495 100644
--- a/kernel/exec_domain.c
+++ b/kernel/exec_domain.c
@@ -34,6 +34,17 @@ static unsigned long ident_map[32] = {
24, 25, 26, 27, 28, 29, 30, 31
};
+#ifdef CONFIG_COMPAT
+static struct exec_domain linux32_exec_domain = {
+ .name = "Linux32", /* name */
+ .handler = default_handler, /* lcall7 causes a seg fault. */
+ .pers_low = PER_LINUX32,
+ .pers_high = PER_LINUX32,
+ .signal_map = ident_map, /* Identity map signals. */
+ .signal_invmap = ident_map, /* - both ways. */
+};
+#endif
+
struct exec_domain default_exec_domain = {
.name = "Linux", /* name */
.handler = default_handler, /* lcall7 causes a seg fault. */
@@ -41,6 +52,9 @@ struct exec_domain default_exec_domain = {
.pers_high = 0, /* PER_LINUX personality. */
.signal_map = ident_map, /* Identity map signals. */
.signal_invmap = ident_map, /* - both ways. */
+#ifdef CONFIG_COMPAT
+ .next = &linux32_exec_domain,
+#endif
};
--
1.7.2.3