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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 4b87c32..a664d57 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -291,10 +291,10 @@
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 @@
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 @@
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 @@
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 @@
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