linux/arch/x86/um/sys_call_table_64.c
Daniel Borkmann b485342bd7 x86, um: actually mark system call tables readonly
Commit a074335a37 ("x86, um: Mark system call tables readonly") was
supposed to mark the sys_call_table in UML as RO by adding the const,
but it doesn't have the desired effect as it's nevertheless being placed
into the data section since __cacheline_aligned enforces sys_call_table
being placed into .data..cacheline_aligned instead. We need to use
the ____cacheline_aligned version instead to fix this issue.

Before:

$ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table"
                 U sys_writev
0000000000000000 D sys_call_table
0000000000000000 D syscall_table_size

After:

$ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table"
                 U sys_writev
0000000000000000 R sys_call_table
0000000000000000 D syscall_table_size

Fixes: a074335a37 ("x86, um: Mark system call tables readonly")
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
2015-01-04 14:21:25 +01:00

60 lines
1.5 KiB
C

/*
* System call table for UML/x86-64, copied from arch/x86/kernel/syscall_*.c
* with some changes for UML.
*/
#include <linux/linkage.h>
#include <linux/sys.h>
#include <linux/cache.h>
#include <generated/user_constants.h>
#define __NO_STUBS
/*
* Below you can see, in terms of #define's, the differences between the x86-64
* and the UML syscall table.
*/
/* Not going to be implemented by UML, since we have no hardware. */
#define stub_iopl sys_ni_syscall
#define sys_ioperm sys_ni_syscall
/*
* The UML TLS problem. Note that x86_64 does not implement this, so the below
* is needed only for the ia32 compatibility.
*/
/* On UML we call it this way ("old" means it's not mmap2) */
#define sys_mmap old_mmap
#define stub_clone sys_clone
#define stub_fork sys_fork
#define stub_vfork sys_vfork
#define stub_execve sys_execve
#define stub_execveat sys_execveat
#define stub_rt_sigreturn sys_rt_sigreturn
#define __SYSCALL_COMMON(nr, sym, compat) __SYSCALL_64(nr, sym, compat)
#define __SYSCALL_X32(nr, sym, compat) /* Not supported */
#define __SYSCALL_64(nr, sym, compat) extern asmlinkage void sym(void) ;
#include <asm/syscalls_64.h>
#undef __SYSCALL_64
#define __SYSCALL_64(nr, sym, compat) [ nr ] = sym,
typedef void (*sys_call_ptr_t)(void);
extern void sys_ni_syscall(void);
const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = {
/*
* Smells like a compiler bug -- it doesn't work
* when the & below is removed.
*/
[0 ... __NR_syscall_max] = &sys_ni_syscall,
#include <asm/syscalls_64.h>
};
int syscall_table_size = sizeof(sys_call_table);