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

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

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org
This commit is contained in:
Andy Lutomirski 2019-11-20 09:56:36 +01:00 committed by Peter Zijlstra
parent 4c4fd55d3d
commit 82cb8a0b1d
1 changed files with 35 additions and 31 deletions
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66
arch/x86/entry/entry_32.S
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@ -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