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| author | Andy Lutomirski <luto@amacapital.net> | 2015-03-05 01:09:44 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-03-18 13:31:25 +0100 |
| commit | 213c9f19d733b067b278901acf49d67e805a38b0 (patch) | |
| tree | 03357d192a1b8c766010ce9a80dae33d39168feb /arch/x86/kernel/entry_64.S | |
| parent | 6e594e375a311e3d0336317c98809a5ba1b51ce4 (diff) | |
| download | lwn-213c9f19d733b067b278901acf49d67e805a38b0.tar.gz lwn-213c9f19d733b067b278901acf49d67e805a38b0.zip | |
x86/asm/entry/64: Remove a bogus 'ret_from_fork' optimization
commit 956421fbb74c3a6261903f3836c0740187cf038b upstream.
'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
[ Backported from tip:x86/asm. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
| -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 02553d6d183d..06469ee0f26e 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -542,11 +542,14 @@ ENTRY(ret_from_fork) testl $3, CS-ARGOFFSET(%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, -ARGOFFSET - 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: subq $REST_SKIP, %rsp # leave space for volatiles |