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SubjectRe: [PATCH] 2.5.68 FUTEX support should be optional
Valdis.Kletnieks@vt.edu wrote:
>
> > Remove kernel features for embedded systems (Y/N)
> >
> > its no more dangerous/hassle than the kernel debug menu
>
> OK.. I know I argued against making it visible to the user at all, but if it's
> phrased like that, it will at least (hopefully) dissuade everybody who
> doesn't know what an embedded system is.
>
> And after all, Linux isn't about dissuading the truly determined, nor is it
> about making moral judgements regarding their wizardry/idiocy ratio....

I'd agree with all that. I've updated the initial patch thusly:

General setup --->
[*] Remove kernel features for embedded systems
Removable kernel features for embedded systems --->
[ ] Enable futex support

So enabling CONFIG_EMBEDDED causes the user to be offered CONFIG_FUTEX, and
there are appropriate stern warnings everywhere.


init/Kconfig | 24 +++++++++++++++++++++++-
kernel/Makefile | 3 ++-
kernel/compat.c | 5 +++--
kernel/sys.c | 2 ++
5 files changed, 32 insertions(+), 4 deletions(-)
diff -puN init/Kconfig~CONFIG_FUTEX init/Kconfig
--- 25/init/Kconfig~CONFIG_FUTEX 2003-05-16 19:17:34.000000000 -0700
+++ 25-akpm/init/Kconfig 2003-05-16 19:32:43.000000000 -0700
@@ -108,8 +108,31 @@ config LOG_BUF_SHIFT
13 => 8 KB
12 => 4 KB

+
+config EMBEDDED
+ bool "Remove kernel features for embedded systems"
+ default n
+ help
+ This option allows certain base kernel features to be removed from
+ the build. This is for specialized environments which can tolerate
+ a "non-standard" kernel. Only use this if you really know what you
+ are doing.
+
+menu "Removable kernel features for embedded systems"
+ depends on EMBEDDED
+
+config FUTEX
+ bool "Enable futex support"
+ depends on EMBEDDED
+ default y
+ help
+ Disabling this option will cause the kernel to be built without
+ support for "fast userspace mutexes". The resulting kernel may not
+ run glibc-based applications correctly.
+
endmenu

+endmenu

menu "Loadable module support"

@@ -181,4 +204,3 @@ config KMOD
in <file:Documentation/kmod.txt>.

endmenu
-
diff -puN kernel/Makefile~CONFIG_FUTEX kernel/Makefile
--- 25/kernel/Makefile~CONFIG_FUTEX 2003-05-16 19:17:34.000000000 -0700
+++ 25-akpm/kernel/Makefile 2003-05-16 19:17:34.000000000 -0700
@@ -5,9 +5,10 @@
obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
exit.o itimer.o time.o softirq.o resource.o \
sysctl.o capability.o ptrace.o timer.o user.o \
- signal.o sys.o kmod.o workqueue.o futex.o pid.o \
+ signal.o sys.o kmod.o workqueue.o pid.o \
rcupdate.o intermodule.o extable.o params.o posix-timers.o

+obj-$(CONFIG_FUTEX) += futex.o
obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
obj-$(CONFIG_SMP) += cpu.o
obj-$(CONFIG_LOCKMETER) += lockmeter.o
diff -puN kernel/sys.c~CONFIG_FUTEX kernel/sys.c
--- 25/kernel/sys.c~CONFIG_FUTEX 2003-05-16 19:17:34.000000000 -0700
+++ 25-akpm/kernel/sys.c 2003-05-16 19:17:34.000000000 -0700
@@ -228,6 +228,8 @@ cond_syscall(sys_shutdown)
cond_syscall(sys_sendmsg)
cond_syscall(sys_recvmsg)
cond_syscall(sys_socketcall)
+cond_syscall(sys_futex)
+cond_syscall(compat_sys_futex)

static int set_one_prio(struct task_struct *p, int niceval, int error)
{
diff -puN kernel/compat.c~CONFIG_FUTEX kernel/compat.c
--- 25/kernel/compat.c~CONFIG_FUTEX 2003-05-16 19:17:34.000000000 -0700
+++ 25-akpm/kernel/compat.c 2003-05-16 19:17:34.000000000 -0700
@@ -18,6 +18,7 @@
#include <linux/signal.h>
#include <linux/sched.h> /* for MAX_SCHEDULE_TIMEOUT */
#include <linux/futex.h> /* for FUTEX_WAIT */
+#include <linux/unistd.h>

#include <asm/uaccess.h>

@@ -211,8 +212,7 @@ asmlinkage long compat_sys_sigprocmask(i
return ret;
}

-extern long do_futex(unsigned long, int, int, unsigned long);
-
+#ifdef CONFIG_FUTEX
asmlinkage long compat_sys_futex(u32 *uaddr, int op, int val,
struct compat_timespec *utime)
{
@@ -226,6 +226,7 @@ asmlinkage long compat_sys_futex(u32 *ua
}
return do_futex((unsigned long)uaddr, op, val, timeout);
}
+#endif

asmlinkage long sys_setrlimit(unsigned int resource, struct rlimit *rlim);

diff -puN include/linux/futex.h~CONFIG_FUTEX include/linux/futex.h
--- 25/include/linux/futex.h~CONFIG_FUTEX 2003-05-16 19:17:34.000000000 -0700
+++ 25-akpm/include/linux/futex.h 2003-05-16 19:17:34.000000000 -0700
@@ -8,4 +8,6 @@

extern asmlinkage long sys_futex(u32 __user *uaddr, int op, int val, struct timespec __user *utime);

+long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout);
+
#endif
_

-
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