With paravirt on, we cannot issue operations like swapgs, sysretq,
iretq, cli, sti. So they have to be changed into macros, that will
be later properly replaced for the paravirt case.
The sysretq is a little bit more complicated, and is replaced
by a sequence of three instructions. It is basically because if
we had already issued an swapgs, we would be with a user stack
at this point. So we do it all-in-one.
The clobber list follows the idea of the i386 version closely,
and represents which caller-saved registers are safe to modify
at the point the function is called. So for example, CLBR_ANY
says we can clobber rax, rdi, rsi, rdx, rcx, r8-r11, while
CLBR_NONE says we cannot touch annything.
[ updates from v1
* renamed SYSRETQ to SYSCALL_RETURN
* don't use ENTRY/ENDPROC for native_{syscall_return,iret}
* fix one use of the clobber list
* rename SWAPGS_NOSTACK to SWAPGS_UNSAFE_STACK
* change the unexpressive 1b label to do_iret
All suggested by Andi Kleen
]
Signed-off-by: Glauber de Oliveira Costa <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
---
arch/x86_64/kernel/entry.S | 130 +++++++++++++++++++++++++++++---------------
1 files changed, 87 insertions(+), 43 deletions(-)
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 1d232e5..db8707a 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -51,8 +51,31 @@
#include <asm/page.h>
#include <asm/irqflags.h>
+#ifdef CONFIG_PARAVIRT
+#include <asm/paravirt.h>
+#else
+#define ENABLE_INTERRUPTS(x) sti
+#define DISABLE_INTERRUPTS(x) cli
+#define INTERRUPT_RETURN iretq
+#define SWAPGS swapgs
+#define SYSCALL_RETURN \
+ movq %gs:pda_oldrsp,%rsp; \
+ swapgs; \
+ sysretq;
+#endif
+
.code64
+/* Currently paravirt can't handle swapgs nicely when we
+ * don't have a stack we can rely on (such as a user space
+ * stack). So we either find a way around these or just fault
+ * and emulate if a guest tries to call swapgs directly.
+ *
+ * Either way, this is a good way to document that we don't
+ * have a reliable stack.
+ */
+#define SWAPGS_UNSAFE_STACK swapgs
+
#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif
@@ -216,14 +239,23 @@ ENTRY(system_call)
CFI_DEF_CFA rsp,PDA_STACKOFFSET
CFI_REGISTER rip,rcx
/*CFI_REGISTER rflags,r11*/
- swapgs
+ SWAPGS_UNSAFE_STACK
+#ifdef CONFIG_PARAVIRT
+ /*
+ * A hypervisor implementation might want to use a label
+ * after the swapgs, so that it can do the swapgs
+ * for the guest and jump here on syscall.
+ */
+ .globl system_call_after_swapgs
+system_call_after_swapgs:
+#endif
movq %rsp,%gs:pda_oldrsp
movq %gs:pda_kernelstack,%rsp
/*
* No need to follow this irqs off/on section - it's straight
* and short:
*/
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
SAVE_ARGS 8,1
movq %rax,ORIG_RAX-ARGOFFSET(%rsp)
movq %rcx,RIP-ARGOFFSET(%rsp)
@@ -245,7 +277,7 @@ ret_from_sys_call:
/* edi: flagmask */
sysret_check:
GET_THREAD_INFO(%rcx)
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
movl threadinfo_flags(%rcx),%edx
andl %edi,%edx
@@ -259,9 +291,7 @@ sysret_check:
CFI_REGISTER rip,rcx
RESTORE_ARGS 0,-ARG_SKIP,1
/*CFI_REGISTER rflags,r11*/
- movq %gs:pda_oldrsp,%rsp
- swapgs
- sysretq
+ SYSCALL_RETURN
CFI_RESTORE_STATE
/* Handle reschedules */
@@ -270,7 +300,7 @@ sysret_careful:
bt $TIF_NEED_RESCHED,%edx
jnc sysret_signal
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
call schedule
@@ -281,7 +311,7 @@ sysret_careful:
/* Handle a signal */
sysret_signal:
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
testl $(_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx
jz 1f
@@ -294,7 +324,7 @@ sysret_signal:
1: movl $_TIF_NEED_RESCHED,%edi
/* Use IRET because user could have changed frame. This
works because ptregscall_common has called FIXUP_TOP_OF_STACK. */
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp int_with_check
@@ -326,7 +356,7 @@ tracesys:
*/
.globl int_ret_from_sys_call
int_ret_from_sys_call:
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
testl $3,CS-ARGOFFSET(%rsp)
je retint_restore_args
@@ -347,20 +377,20 @@ int_careful:
bt $TIF_NEED_RESCHED,%edx
jnc int_very_careful
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
call schedule
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp int_with_check
/* handle signals and tracing -- both require a full stack frame */
int_very_careful:
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
SAVE_REST
/* Check for syscall exit trace */
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP),%edx
@@ -383,7 +413,7 @@ int_signal:
1: movl $_TIF_NEED_RESCHED,%edi
int_restore_rest:
RESTORE_REST
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp int_with_check
CFI_ENDPROC
@@ -504,7 +534,7 @@ END(stub_rt_sigreturn)
CFI_DEF_CFA_REGISTER rbp
testl $3,CS(%rdi)
je 1f
- swapgs
+ SWAPGS
/* irqcount is used to check if a CPU is already on an interrupt
stack or not. While this is essentially redundant with preempt_count
it is a little cheaper to use a separate counter in the PDA
@@ -525,7 +555,7 @@ ENTRY(common_interrupt)
interrupt do_IRQ
/* 0(%rsp): oldrsp-ARGOFFSET */
ret_from_intr:
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
decl %gs:pda_irqcount
leaveq
@@ -552,13 +582,13 @@ retint_swapgs:
/*
* The iretq could re-enable interrupts:
*/
- cli
+ DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_IRETQ
- swapgs
+ SWAPGS
jmp restore_args
retint_restore_args:
- cli
+ DISABLE_INTERRUPTS(CLBR_ANY)
/*
* The iretq could re-enable interrupts:
*/
@@ -566,10 +596,15 @@ retint_restore_args:
restore_args:
RESTORE_ARGS 0,8,0
iret_label:
+#ifdef CONFIG_PARAVIRT
+ INTERRUPT_RETURN
+#endif
+.globl do_iretq;
+do_iretq:
iretq
.section __ex_table,"a"
- .quad iret_label,bad_iret
+ .quad do_iretq, bad_iret
.previous
.section .fixup,"ax"
/* force a signal here? this matches i386 behaviour */
@@ -577,24 +612,24 @@ iret_label:
bad_iret:
movq $11,%rdi /* SIGSEGV */
TRACE_IRQS_ON
- sti
- jmp do_exit
- .previous
-
+ ENABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI))
+ jmp do_exit
+ .previous
+
/* edi: workmask, edx: work */
retint_careful:
CFI_RESTORE_STATE
bt $TIF_NEED_RESCHED,%edx
jnc retint_signal
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
call schedule
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
GET_THREAD_INFO(%rcx)
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp retint_check
@@ -602,14 +637,14 @@ retint_signal:
testl $(_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY),%edx
jz retint_swapgs
TRACE_IRQS_ON
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
SAVE_REST
movq $-1,ORIG_RAX(%rsp)
xorl %esi,%esi # oldset
movq %rsp,%rdi # &pt_regs
call do_notify_resume
RESTORE_REST
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
movl $_TIF_NEED_RESCHED,%edi
GET_THREAD_INFO(%rcx)
@@ -727,7 +762,7 @@ END(spurious_interrupt)
rdmsr
testl %edx,%edx
js 1f
- swapgs
+ SWAPGS
xorl %ebx,%ebx
1:
.if \ist
@@ -743,7 +778,7 @@ END(spurious_interrupt)
.if \ist
addq $EXCEPTION_STKSZ, per_cpu__init_tss + TSS_ist + (\ist - 1) * 8(%rbp)
.endif
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
.if \irqtrace
TRACE_IRQS_OFF
.endif
@@ -772,10 +807,10 @@ paranoid_swapgs\trace:
.if \trace
TRACE_IRQS_IRETQ 0
.endif
- swapgs
+ SWAPGS_UNSAFE_STACK
paranoid_restore\trace:
RESTORE_ALL 8
- iretq
+ INTERRUPT_RETURN
paranoid_userspace\trace:
GET_THREAD_INFO(%rcx)
movl threadinfo_flags(%rcx),%ebx
@@ -790,11 +825,11 @@ paranoid_userspace\trace:
.if \trace
TRACE_IRQS_ON
.endif
- sti
+ ENABLE_INTERRUPTS(CLBR_NONE)
xorl %esi,%esi /* arg2: oldset */
movq %rsp,%rdi /* arg1: &pt_regs */
call do_notify_resume
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
.if \trace
TRACE_IRQS_OFF
.endif
@@ -803,9 +838,9 @@ paranoid_schedule\trace:
.if \trace
TRACE_IRQS_ON
.endif
- sti
+ ENABLE_INTERRUPTS(CLBR_ANY)
call schedule
- cli
+ DISABLE_INTERRUPTS(CLBR_ANY)
.if \trace
TRACE_IRQS_OFF
.endif
@@ -858,7 +893,7 @@ KPROBE_ENTRY(error_entry)
testl $3,CS(%rsp)
je error_kernelspace
error_swapgs:
- swapgs
+ SWAPGS
error_sti:
movq %rdi,RDI(%rsp)
CFI_REL_OFFSET rdi,RDI
@@ -870,7 +905,7 @@ error_sti:
error_exit:
movl %ebx,%eax
RESTORE_REST
- cli
+ DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
GET_THREAD_INFO(%rcx)
testl %eax,%eax
@@ -883,7 +918,7 @@ error_exit:
* The iret might restore flags:
*/
TRACE_IRQS_IRETQ
- swapgs
+ SWAPGS
RESTORE_ARGS 0,8,0
jmp iret_label
CFI_ENDPROC
@@ -912,12 +947,12 @@ ENTRY(load_gs_index)
CFI_STARTPROC
pushf
CFI_ADJUST_CFA_OFFSET 8
- cli
- swapgs
+ DISABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI))
+ SWAPGS
gs_change:
movl %edi,%gs
2: mfence /* workaround */
- swapgs
+ SWAPGS
popf
CFI_ADJUST_CFA_OFFSET -8
ret
@@ -931,7 +966,7 @@ ENDPROC(load_gs_index)
.section .fixup,"ax"
/* running with kernelgs */
bad_gs:
- swapgs /* switch back to user gs */
+ SWAPGS /* switch back to user gs */
xorl %eax,%eax
movl %eax,%gs
jmp 2b
@@ -1072,6 +1107,15 @@ KPROBE_ENTRY(int3)
CFI_ENDPROC
KPROBE_END(int3)
+#ifdef CONFIG_PARAVIRT
+.globl native_syscall_return;
+native_syscall_return:
+ movq %gs:pda_oldrsp,%rsp
+ swapgs
+ sysretq
+
+#endif /* CONFIG_PARAVIRT */
+
ENTRY(overflow)
zeroentry do_overflow
END(overflow)
--
1.4.4.2
-
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