diff options
| author | Dave Hansen | 2017-10-18 10:21:07 -0700 |
|---|---|---|
| committer | Ingo Molnar | 2017-10-20 10:37:33 +0200 |
| commit | da20ab35180780e4a6eadc804544f1fa967f3567 (patch) | |
| tree | 0c70b8daa761d4013d5bc8b3bb7f9091d7bca2cd /arch/x86/um | |
| parent | fc72ae40e30327aa24eb88a24b9c7058f938bd36 (diff) | |
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>
Diffstat (limited to 'arch/x86/um')
| -rw-r--r-- | arch/x86/um/ldt.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/um/ldt.c b/arch/x86/um/ldt.c index 836a1eb5df43..3ee234b6234d 100644 --- a/arch/x86/um/ldt.c +++ b/arch/x86/um/ldt.c @@ -6,6 +6,7 @@ #include <linux/mm.h> #include <linux/sched.h> #include <linux/slab.h> +#include <linux/syscalls.h> #include <linux/uaccess.h> #include <asm/unistd.h> #include <os.h> @@ -369,7 +370,9 @@ void free_ldt(struct mm_context *mm) mm->arch.ldt.entry_count = 0; } -int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount) +SYSCALL_DEFINE3(modify_ldt, int , func , void __user * , ptr , + unsigned long , bytecount) { - return do_modify_ldt_skas(func, ptr, bytecount); + /* See non-um modify_ldt() for why we do this cast */ + return (unsigned int)do_modify_ldt_skas(func, ptr, bytecount); } |