fs, kernel: permit disabling the uselib syscall

uselib hasn't been used since libc5; glibc does not use it.  Support
turning it off.

When disabled, also omit the load_elf_library implementation from
binfmt_elf.c, which only uselib invokes.

bloat-o-meter:
add/remove: 0/4 grow/shrink: 0/1 up/down: 0/-785 (-785)
function                                     old     new   delta
padzero                                       39      36      -3
uselib_flags                                  20       -     -20
sys_uselib                                   168       -    -168
SyS_uselib                                   168       -    -168
load_elf_library                             426       -    -426

The new CONFIG_USELIB defaults to `y'.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 67be2951b98a..0f59799fa105 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -46,10 +46,15 @@
 #endif
 
 static int load_elf_binary(struct linux_binprm *bprm);
-static int load_elf_library(struct file *);
 static unsigned long elf_map(struct file *, unsigned long, struct elf_phdr *,
                                 int, int, unsigned long);
 
+#ifdef CONFIG_USELIB
+static int load_elf_library(struct file *);
+#else
+#define load_elf_library NULL
+#endif
+
 /*
  * If we don't support core dumping, then supply a NULL so we
  * don't even try.
@@ -1005,6 +1010,7 @@ out_free_ph:
         goto out;
 }
 
+#ifdef CONFIG_USELIB
 /* This is really simpleminded and specialized - we are loading an
    a.out library that is given an ELF header. */
 static int load_elf_library(struct file *file)
@@ -1083,6 +1089,7 @@ out_free_ph:
 out:
         return error;
 }
+#endif /* #ifdef CONFIG_USELIB */
 
 #ifdef CONFIG_ELF_CORE
 /*