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>
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 67be295..0f59799 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 @@
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:
return error;
}
+#endif /* #ifdef CONFIG_USELIB */
#ifdef CONFIG_ELF_CORE
/*
diff --git a/fs/exec.c b/fs/exec.c
index 4f59402..25dfeba 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -97,6 +97,7 @@
module_put(fmt->module);
}
+#ifdef CONFIG_USELIB
/*
* Note that a shared library must be both readable and executable due to
* security reasons.
@@ -156,6 +157,7 @@
out:
return error;
}
+#endif /* #ifdef CONFIG_USELIB */
#ifdef CONFIG_MMU
/*
diff --git a/init/Kconfig b/init/Kconfig
index e45cc62..8114a06 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -273,6 +273,16 @@
get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
syscalls.
+config USELIB
+ bool "uselib syscall"
+ default y
+ help
+ This option enables the uselib syscall, a system call used in the
+ dynamic linker from libc5 and earlier. glibc does not use this
+ system call. If you intend to run programs built on libc5 or
+ earlier, you may need to enable this syscall. Current systems
+ running glibc can safely disable this.
+
config AUDIT
bool "Auditing support"
depends on NET
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 74395a9..bc8d1b7 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -152,6 +152,7 @@
cond_syscall(sys_process_vm_writev);
cond_syscall(compat_sys_process_vm_readv);
cond_syscall(compat_sys_process_vm_writev);
+cond_syscall(sys_uselib);
/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read);