diff options
| author | Andy Lutomirski <luto@amacapital.net> | 2015-02-26 14:40:39 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-03-04 22:50:53 +0100 |
| commit | 1e3fbb8a1d814f35e2e689cf87714d38d9f3564d (patch) | |
| tree | a16fcdfd5d18f59b9ddec985e78c45101444ad96 | |
| parent | d441c1f2b73ec742c2e55be804ebc6fee130c77f (diff) | |
x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization
'ret_from_fork' checks TIF_IA32 to determine whether 'pt_regs' and
the related state make sense for 'ret_from_sys_call'. This is
entirely the wrong check. TS_COMPAT would make a little more
sense, but there's really no point in keeping this optimization
at all.
This fixes a return to the wrong user CS if we came from int
0x80 in a 64-bit task.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/4710be56d76ef994ddf59087aad98c000fbab9a4.1424989793.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bc1527889c40..622ce4254893 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -550,11 +550,14 @@ ENTRY(ret_from_fork) testl $3,CS(%rsp) # from kernel_thread? jz 1f - testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET - jnz int_ret_from_sys_call - - RESTORE_TOP_OF_STACK %rdi - jmp ret_from_sys_call # go to the SYSRET fastpath + /* + * By the time we get here, we have no idea whether our pt_regs, + * ti flags, and ti status came from the 64-bit SYSCALL fast path, + * the slow path, or one of the ia32entry paths. + * Use int_ret_from_sys_call to return, since it can safely handle + * all of the above. + */ + jmp int_ret_from_sys_call 1: movq %rbp, %rdi |