lkml.org 
[lkml]   [2017]   [Oct]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] x86, syscalls: use SYSCALL_DEFINE() macros for sys_modify_ldt()
On Tue, Oct 17, 2017 at 12:22 PM, Dave Hansen
<dave.hansen@linux.intel.com> wrote:
>
> 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().

Reviewed-by: Brian Gerst <brgerst@gmail.com>

\
 
 \ /
  Last update: 2017-10-22 17:14    [W:0.090 / U:0.604 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site