alpha: binfmt_aout fix

This fixes the problem introduced by commit 3bfacef412 (get rid of
special-casing the /sbin/loader on alpha): osf/1 ecoff binary segfaults
when binfmt_aout built as module.  That happens because aout binary
handler gets on the top of the binfmt list due to late registration, and
kernel attempts to execute the binary without preparatory work that must
be done by binfmt_loader.

Fixed by changing the registration order of the default binfmt handlers
using list_add_tail() and introducing insert_binfmt() function which
places new handler on the top of the binfmt list.  This might be generally
useful for installing arch-specific frontends for default handlers or just
for overriding them.

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Richard Henderson <rth@twiddle.net
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/alpha/kernel/Makefile b/arch/alpha/kernel/Makefile
index a427538252f878aa664520e5c3f6f6d7ee844513..7739a62440a7a7027e241385171827189f783dd8 100644 (file)
--- a/arch/alpha/kernel/Makefile
+++ b/arch/alpha/kernel/Makefile
@@ -8,7 +8,7 @@ EXTRA_CFLAGS    := -Werror -Wno-sign-compare
 
 obj-y    := entry.o traps.o process.o init_task.o osf_sys.o irq.o \
            irq_alpha.o signal.o setup.o ptrace.o time.o \
-           alpha_ksyms.o systbls.o err_common.o io.o binfmt_loader.o
+           alpha_ksyms.o systbls.o err_common.o io.o
 
 obj-$(CONFIG_VGA_HOSE) += console.o
 obj-$(CONFIG_SMP)      += smp.o
@@ -43,6 +43,10 @@ else
 # Misc support
 obj-$(CONFIG_ALPHA_SRM)                += srmcons.o
 
+ifdef CONFIG_BINFMT_AOUT
+obj-y  += binfmt_loader.o
+endif
+
 # Core logic support
 obj-$(CONFIG_ALPHA_APECS)      += core_apecs.o
 obj-$(CONFIG_ALPHA_CIA)                += core_cia.o

diff --git a/arch/alpha/kernel/binfmt_loader.c b/arch/alpha/kernel/binfmt_loader.c
index 4a0af906b00aff98efa3db10d0e2797f3899bf28..3fcfad4101300ea1a94992022f4b5084d119d0f9 100644 (file)
--- a/arch/alpha/kernel/binfmt_loader.c
+++ b/arch/alpha/kernel/binfmt_loader.c
@@ -46,6 +46,6 @@ static struct linux_binfmt loader_format = {
 
 static int __init init_loader_binfmt(void)
 {
-       return register_binfmt(&loader_format);
+       return insert_binfmt(&loader_format);
 }
 arch_initcall(init_loader_binfmt);

diff --git a/fs/exec.c b/fs/exec.c
index a3a8ce83940f1dfdfeb2430571f6dc19359e253f..639177b0eeac9bc74ccaca2c1b2f6296f7b0f23d 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -69,17 +69,18 @@ int suid_dumpable = 0;
 static LIST_HEAD(formats);
 static DEFINE_RWLOCK(binfmt_lock);
 
-int register_binfmt(struct linux_binfmt * fmt)
+int __register_binfmt(struct linux_binfmt * fmt, int insert)
 {
        if (!fmt)
                return -EINVAL;
        write_lock(&binfmt_lock);
-       list_add(&fmt->lh, &formats);
+       insert ? list_add(&fmt->lh, &formats) :
+                list_add_tail(&fmt->lh, &formats);
        write_unlock(&binfmt_lock);
        return 0;       
 }
 
-EXPORT_SYMBOL(register_binfmt);
+EXPORT_SYMBOL(__register_binfmt);
 
 void unregister_binfmt(struct linux_binfmt * fmt)
 {

diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 6638b8148de7d9a45635ca95b6952b6651df2542..61ee18c1bdb44bd714b39b840d7b73b4ad02698a 100644 (file)
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -82,7 +82,19 @@ struct linux_binfmt {
        int hasvdso;
 };
 
-extern int register_binfmt(struct linux_binfmt *);
+extern int __register_binfmt(struct linux_binfmt *fmt, int insert);
+
+/* Registration of default binfmt handlers */
+static inline int register_binfmt(struct linux_binfmt *fmt)
+{
+       return __register_binfmt(fmt, 0);
+}
+/* Same as above, but adds a new binfmt at the top of the list */
+static inline int insert_binfmt(struct linux_binfmt *fmt)
+{
+       return __register_binfmt(fmt, 1);
+}
+
 extern void unregister_binfmt(struct linux_binfmt *);
 
 extern int prepare_binprm(struct linux_binprm *);