Commit 82cb8a0b authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Peter Zijlstra
Browse files

x86/entry/32: Move FIXUP_FRAME after pushing %fs in SAVE_ALL 



This will allow us to get percpu access working before FIXUP_FRAME,
which will allow us to unwind ESPFIX earlier.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org
parent 4c4fd55d

arch/x86/entry/entry_32.S

+35 −31
Original line number Diff line number Diff line
@@ -213,54 +213,58 @@ 
	 *

	 * Be careful: we may have nonzero SS base due to ESPFIX.

	 */

	andl	$0x0000ffff, 3*4(%esp)

	andl	$0x0000ffff, 4*4(%esp)



#ifdef CONFIG_VM86

	testl	$X86_EFLAGS_VM, 4*4(%esp)

	testl	$X86_EFLAGS_VM, 5*4(%esp)

	jnz	.Lfrom_usermode_no_fixup_\@

#endif

	testl	$USER_SEGMENT_RPL_MASK, 3*4(%esp)

	testl	$USER_SEGMENT_RPL_MASK, 4*4(%esp)

	jnz	.Lfrom_usermode_no_fixup_\@



	orl	$CS_FROM_KERNEL, 3*4(%esp)

	orl	$CS_FROM_KERNEL, 4*4(%esp)



	/*

	 * When we're here from kernel mode; the (exception) stack looks like:

	 *

	 *  5*4(%esp) - <previous context>

	 *  4*4(%esp) - flags

	 *  3*4(%esp) - cs

	 *  2*4(%esp) - ip

	 *  1*4(%esp) - orig_eax

	 *  0*4(%esp) - gs / function

	 *  6*4(%esp) - <previous context>

	 *  5*4(%esp) - flags

	 *  4*4(%esp) - cs

	 *  3*4(%esp) - ip

	 *  2*4(%esp) - orig_eax

	 *  1*4(%esp) - gs / function

	 *  0*4(%esp) - fs

	 *

	 * Lets build a 5 entry IRET frame after that, such that struct pt_regs

	 * is complete and in particular regs->sp is correct. This gives us

	 * the original 5 enties as gap:

	 * the original 6 enties as gap:

	 *

	 * 12*4(%esp) - <previous context>

	 * 11*4(%esp) - gap / flags

	 * 10*4(%esp) - gap / cs

	 *  9*4(%esp) - gap / ip

	 *  8*4(%esp) - gap / orig_eax

	 *  7*4(%esp) - gap / gs / function

	 *  6*4(%esp) - ss

	 *  5*4(%esp) - sp

	 *  4*4(%esp) - flags

	 *  3*4(%esp) - cs

	 *  2*4(%esp) - ip

	 *  1*4(%esp) - orig_eax

	 *  0*4(%esp) - gs / function

	 * 14*4(%esp) - <previous context>

	 * 13*4(%esp) - gap / flags

	 * 12*4(%esp) - gap / cs

	 * 11*4(%esp) - gap / ip

	 * 10*4(%esp) - gap / orig_eax

	 *  9*4(%esp) - gap / gs / function

	 *  8*4(%esp) - gap / fs

	 *  7*4(%esp) - ss

	 *  6*4(%esp) - sp

	 *  5*4(%esp) - flags

	 *  4*4(%esp) - cs

	 *  3*4(%esp) - ip

	 *  2*4(%esp) - orig_eax

	 *  1*4(%esp) - gs / function

	 *  0*4(%esp) - fs

	 */



	pushl	%ss		# ss

	pushl	%esp		# sp (points at ss)

	addl	$6*4, (%esp)	# point sp back at the previous context

	pushl	6*4(%esp)	# flags

	pushl	6*4(%esp)	# cs

	pushl	6*4(%esp)	# ip

	pushl	6*4(%esp)	# orig_eax

	pushl	6*4(%esp)	# gs / function

	addl	$7*4, (%esp)	# point sp back at the previous context

	pushl	7*4(%esp)	# flags

	pushl	7*4(%esp)	# cs

	pushl	7*4(%esp)	# ip

	pushl	7*4(%esp)	# orig_eax

	pushl	7*4(%esp)	# gs / function

	pushl	7*4(%esp)	# fs

.Lfrom_usermode_no_fixup_\@:

.endm
@@ -308,8 +312,8 @@ 
.if \skip_gs == 0

	PUSH_GS

.endif

	FIXUP_FRAME

	pushl	%fs

	FIXUP_FRAME

	pushl	%es

	pushl	%ds

	pushl	\pt_regs_ax