linux/arch/x86/include/asm/syscalls.h
Dave Hansen da20ab3518 x86/entry: Use SYSCALL_DEFINE() macros for sys_modify_ldt()
We do not have tracepoints for sys_modify_ldt() because we define
it directly instead of using the normal SYSCALL_DEFINEx() macros.

However, there is a reason sys_modify_ldt() does not use the macros:
it has an 'int' return type instead of 'unsigned long'.  This is
a bug, but it's a bug cemented in the ABI.

What does this mean?  If we return -EINVAL from a function that
returns 'int', we have 0x00000000ffffffea in %rax.  But, if we
return -EINVAL from a function returning 'unsigned long', we end
up with 0xffffffffffffffea in %rax, which is wrong.

To work around this and maintain the 'int' behavior while using
the SYSCALL_DEFINEx() macros, so we add a cast to 'unsigned int'
in both implementations of sys_modify_ldt().

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Brian Gerst <brgerst@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20171018172107.1A79C532@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-20 10:37:33 +02:00

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1.4 KiB
C

/*
* syscalls.h - Linux syscall interfaces (arch-specific)
*
* Copyright (c) 2008 Jaswinder Singh Rajput
*
* This file is released under the GPLv2.
* See the file COPYING for more details.
*/
#ifndef _ASM_X86_SYSCALLS_H
#define _ASM_X86_SYSCALLS_H
#include <linux/compiler.h>
#include <linux/linkage.h>
#include <linux/signal.h>
#include <linux/types.h>
/* Common in X86_32 and X86_64 */
/* kernel/ioport.c */
asmlinkage long sys_ioperm(unsigned long, unsigned long, int);
asmlinkage long sys_iopl(unsigned int);
/* kernel/ldt.c */
asmlinkage long sys_modify_ldt(int, void __user *, unsigned long);
/* kernel/signal.c */
asmlinkage long sys_rt_sigreturn(void);
/* kernel/tls.c */
asmlinkage long sys_set_thread_area(struct user_desc __user *);
asmlinkage long sys_get_thread_area(struct user_desc __user *);
/* X86_32 only */
#ifdef CONFIG_X86_32
/* kernel/signal.c */
asmlinkage unsigned long sys_sigreturn(void);
/* kernel/vm86_32.c */
struct vm86_struct;
asmlinkage long sys_vm86old(struct vm86_struct __user *);
asmlinkage long sys_vm86(unsigned long, unsigned long);
#else /* CONFIG_X86_32 */
/* X86_64 only */
/* kernel/process_64.c */
asmlinkage long sys_arch_prctl(int, unsigned long);
/* kernel/sys_x86_64.c */
asmlinkage long sys_mmap(unsigned long, unsigned long, unsigned long,
unsigned long, unsigned long, unsigned long);
#endif /* CONFIG_X86_32 */
#endif /* _ASM_X86_SYSCALLS_H */