From: Andy Lutomirski luto@kernel.org
commit 82cb8a0b1d8d07817b5d59f7fa1438e1fceafab2 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/entry/entry_32.S | 66 ++++++++++++++++++++++++---------------------- 1 file changed, 35 insertions(+), 31 deletions(-)
--- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -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