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x86/entry/64: Really create an error-entry-from-usermode code path

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In 539f51136500 ("x86/asm/entry/64: Disentangle error_entry/exit
gsbase/ebx/usermode code"), I arranged the code slightly wrong
-- IRET faults would skip the code path that was intended to
execute on all error entries from user mode.  Fix it up.

While we're at it, make all the labels in error_entry local.

This does not fix a bug, but we'll need it, and it slightly
shrinks the code.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/91e17891e49fa3d61357eadc451529ad48143ee1.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-07-03 12:44:27 -07:00 committed by Ingo Molnar
parent c5c46f59e4
commit cb6f64ed5a
1 changed files with 16 additions and 12 deletions
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28
arch/x86/entry/entry_64.S
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@ -1143,12 +1143,17 @@ ENTRY(error_entry)
SAVE_EXTRA_REGS 8
xorl %ebx, %ebx
testb $3, CS+8(%rsp)
jz error_kernelspace
jz .Lerror_kernelspace
/* We entered from user mode */
.Lerror_entry_from_usermode_swapgs:
/*
* We entered from user mode or we're pretending to have entered
* from user mode due to an IRET fault.
*/
SWAPGS
error_entry_done:
.Lerror_entry_from_usermode_after_swapgs:
.Lerror_entry_done:
TRACE_IRQS_OFF
ret
@ -1158,31 +1163,30 @@ error_entry_done:
* truncated RIP for IRET exceptions returning to compat mode. Check
* for these here too.
*/
error_kernelspace:
.Lerror_kernelspace:
incl %ebx
leaq native_irq_return_iret(%rip), %rcx
cmpq %rcx, RIP+8(%rsp)
je error_bad_iret
je .Lerror_bad_iret
movl %ecx, %eax /* zero extend */
cmpq %rax, RIP+8(%rsp)
je bstep_iret
je .Lbstep_iret
cmpq $gs_change, RIP+8(%rsp)
jne error_entry_done
jne .Lerror_entry_done
/*
* hack: gs_change can fail with user gsbase. If this happens, fix up
* gsbase and proceed. We'll fix up the exception and land in
* gs_change's error handler with kernel gsbase.
*/
SWAPGS
jmp error_entry_done
jmp .Lerror_entry_from_usermode_swapgs
bstep_iret:
.Lbstep_iret:
/* Fix truncated RIP */
movq %rcx, RIP+8(%rsp)
/* fall through */
error_bad_iret:
.Lerror_bad_iret:
/*
* We came from an IRET to user mode, so we have user gsbase.
* Switch to kernel gsbase:
@ -1198,7 +1202,7 @@ error_bad_iret:
call fixup_bad_iret
mov %rax, %rsp
decl %ebx
jmp error_entry_done
jmp .Lerror_entry_from_usermode_after_swapgs
END(error_entry)