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fs, kernel: permit disabling the uselib syscall

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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>
This commit is contained in:
Josh Triplett 2014-04-03 14:48:27 -07:00 committed by Linus Torvalds
parent 8f6c5ffc89
commit 69369a7003
4 changed files with 21 additions and 1 deletions
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9
fs/binfmt_elf.c
View file

@ -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 @@ static int load_elf_binary(struct linux_binprm *bprm)
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 @@ static int load_elf_library(struct file *file)
out:
return error;
}
#endif /* #ifdef CONFIG_USELIB */
#ifdef CONFIG_ELF_CORE
/*

2
fs/exec.c
View file

@ -97,6 +97,7 @@ static inline void put_binfmt(struct linux_binfmt * fmt)
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 @@ SYSCALL_DEFINE1(uselib, const char __user *, library)
out:
return error;
}
#endif /* #ifdef CONFIG_USELIB */
#ifdef CONFIG_MMU
/*

10
init/Kconfig
View file

@ -273,6 +273,16 @@ config FHANDLE
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

1
kernel/sys_ni.c
View file

@ -152,6 +152,7 @@ cond_syscall(sys_process_vm_readv);
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);