Commit d93c870b authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
Browse files

x86: only enable interrupts when kernel state has been set up 



The sysenter path tries to enable interrupts immediately.  Unfortunately
this doesn't work in a paravirt environment, because not enough kernel
state has been set up at that point (namely, pointing %fs to the kernel
percpu data segment).  To fix this, defer ENABLE_INTERRUPTS until after
the kernel state has been set up.

Unfortunately this means that we're running with interrupts disabled
for a while without calling the IRQ tracing code, but that can't be
called without setting up %fs either.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 687c8054

arch/x86/kernel/entry_32.S

+10 −9
Original line number Diff line number Diff line
@@ -291,10 +291,10 @@ ENTRY(ia32_sysenter_target) 
	movl TSS_sysenter_sp0(%esp),%esp

sysenter_past_esp:

	/*

	 * No need to follow this irqs on/off section: the syscall

	 * disabled irqs and here we enable it straight after entry:

	 * Interrupts are disabled here, but we can't trace it until

	 * enough kernel state to call TRACE_IRQS_OFF can be called - but

	 * we immediately enable interrupts at that point anyway.

	 */

	ENABLE_INTERRUPTS(CLBR_NONE)

	pushl $(__USER_DS)

	CFI_ADJUST_CFA_OFFSET 4

	/*CFI_REL_OFFSET ss, 0*/
@@ -302,6 +302,7 @@ sysenter_past_esp: 
	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET esp, 0

	pushfl

	orl $X86_EFLAGS_IF, (%esp)

	CFI_ADJUST_CFA_OFFSET 4

	pushl $(__USER_CS)

	CFI_ADJUST_CFA_OFFSET 4
@@ -315,6 +316,11 @@ sysenter_past_esp: 
	CFI_ADJUST_CFA_OFFSET 4

	CFI_REL_OFFSET eip, 0



	pushl %eax

	CFI_ADJUST_CFA_OFFSET 4

	SAVE_ALL

	ENABLE_INTERRUPTS(CLBR_NONE)



/*

 * Load the potential sixth argument from user stack.

 * Careful about security.
@@ -322,14 +328,12 @@ sysenter_past_esp: 
	cmpl $__PAGE_OFFSET-3,%ebp

	jae syscall_fault

1:	movl (%ebp),%ebp

	movl %ebp,PT_EBP(%esp)

.section __ex_table,"a"

	.align 4

	.long 1b,syscall_fault

.previous



	pushl %eax

	CFI_ADJUST_CFA_OFFSET 4

	SAVE_ALL

	GET_THREAD_INFO(%ebp)



	/* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
@@ -543,9 +547,6 @@ END(syscall_exit_work) 


	RING0_INT_FRAME			# can't unwind into user space anyway

syscall_fault:

	pushl %eax			# save orig_eax

	CFI_ADJUST_CFA_OFFSET 4

	SAVE_ALL

	GET_THREAD_INFO(%ebp)

	movl $-EFAULT,PT_EAX(%esp)

	jmp resume_userspace