[PATCH 30 of 36] x86/paravirt_ops: split sysret and sysexit

Jeremy Fitzhardinge
2008-06-25T04:45:40Z

Don't conflate sysret and sysexit; they're different instructions with
different semantics, and may be in use at the same time (at least
within the same kernel, depending on whether its an Intel or AMD
system).

sysexit - just return to userspace, does no register restoration of
any kind; must explicitly atomically enable interrupts.

sysret - reloads flags from r11, so no need to explicitly enable
interrupts on 64-bit, responsible for restoring usermode %gs

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citirx.com>
---
arch/x86/kernel/asm-offsets_32.c | 2 +-
arch/x86/kernel/asm-offsets_64.c | 2 +-
arch/x86/kernel/entry_32.S | 8 ++++----
arch/x86/kernel/entry_64.S | 4 ++--
arch/x86/kernel/paravirt.c | 12 +++++++++---
arch/x86/kernel/paravirt_patch_32.c | 4 ++--
arch/x86/kernel/paravirt_patch_64.c | 4 ++--
arch/x86/kernel/vmi_32.c | 4 ++--
arch/x86/xen/enlighten.c | 2 +-
include/asm-x86/irqflags.h | 4 ++--
include/asm-x86/paravirt.h | 15 ++++++++++-----
11 files changed, 36 insertions(+), 25 deletions(-)

diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -112,7 +112,7 @@
OFFSET(PV_IRQ_irq_enable, pv_irq_ops, irq_enable);
OFFSET(PV_CPU_iret, pv_cpu_ops, iret);
OFFSET(PV_CPU_nmi_return, pv_cpu_ops, nmi_return);
- OFFSET(PV_CPU_irq_enable_syscall_ret, pv_cpu_ops, irq_enable_syscall_ret);
+ OFFSET(PV_CPU_irq_enable_sysexit, pv_cpu_ops, irq_enable_sysexit);
OFFSET(PV_CPU_read_cr0, pv_cpu_ops, read_cr0);
#endif

diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -63,7 +63,7 @@
OFFSET(PV_IRQ_irq_enable, pv_irq_ops, irq_enable);
OFFSET(PV_CPU_iret, pv_cpu_ops, iret);
OFFSET(PV_CPU_nmi_return, pv_cpu_ops, nmi_return);
- OFFSET(PV_CPU_irq_enable_syscall_ret, pv_cpu_ops, irq_enable_syscall_ret);
+ OFFSET(PV_CPU_usersp_sysret, pv_cpu_ops, usersp_sysret);
OFFSET(PV_CPU_swapgs, pv_cpu_ops, swapgs);
OFFSET(PV_MMU_read_cr2, pv_mmu_ops, read_cr2);
#endif
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -59,7 +59,7 @@
* for paravirtualization. The following will never clobber any registers:
* INTERRUPT_RETURN (aka. "iret")
* GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")
- * ENABLE_INTERRUPTS_SYSCALL_RET (aka "sti; sysexit").
+ * ENABLE_INTERRUPTS_SYSEXIT (aka "sti; sysexit").
*
* For DISABLE_INTERRUPTS/ENABLE_INTERRUPTS (aka "cli"/"sti"), you must
* specify what registers can be overwritten (CLBR_NONE, CLBR_EAX/EDX/ECX/ANY).
@@ -376,7 +376,7 @@
xorl %ebp,%ebp
TRACE_IRQS_ON
1: mov PT_FS(%esp), %fs
- ENABLE_INTERRUPTS_SYSCALL_RET
+ ENABLE_INTERRUPTS_SYSEXIT
CFI_ENDPROC
.pushsection .fixup,"ax"
2: movl $0,PT_FS(%esp)
@@ -905,10 +905,10 @@
NATIVE_INTERRUPT_RETURN_NMI_SAFE # Should we deal with popf exception ?
END(native_nmi_return)

-ENTRY(native_irq_enable_syscall_ret)
+ENTRY(native_irq_enable_sysexit)
sti
sysexit
-END(native_irq_enable_syscall_ret)
+END(native_irq_enable_sysexit)
#endif

KPROBE_ENTRY(int3)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -167,7 +167,7 @@
#endif

#ifdef CONFIG_PARAVIRT
-ENTRY(native_irq_enable_syscall_ret)
+ENTRY(native_usersp_sysret)
movq %gs:pda_oldrsp,%rsp
swapgs
sysretq
@@ -383,7 +383,7 @@
CFI_REGISTER rip,rcx
RESTORE_ARGS 0,-ARG_SKIP,1
/*CFI_REGISTER rflags,r11*/
- ENABLE_INTERRUPTS_SYSCALL_RET
+ USERSP_SYSRET

CFI_RESTORE_STATE
/* Handle reschedules */
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -141,7 +141,8 @@
ret = paravirt_patch_nop();
else if (type == PARAVIRT_PATCH(pv_cpu_ops.iret) ||
type == PARAVIRT_PATCH(pv_cpu_ops.nmi_return) ||
- type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_syscall_ret))
+ type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit) ||
+ type == PARAVIRT_PATCH(pv_cpu_ops.usersp_sysret))
/* If operation requires a jmp, then jmp */
ret = paravirt_patch_jmp(insnbuf, opfunc, addr, len);
else
@@ -193,7 +194,8 @@
/* These are in entry.S */
extern void native_iret(void);
extern void native_nmi_return(void);
-extern void native_irq_enable_syscall_ret(void);
+extern void native_irq_enable_sysexit(void);
+extern void native_usersp_sysret(void);

static int __init print_banner(void)
{
@@ -329,7 +331,11 @@
.write_idt_entry = native_write_idt_entry,
.load_sp0 = native_load_sp0,

- .irq_enable_syscall_ret = native_irq_enable_syscall_ret,
+#ifdef CONFIG_X86_32
+ .irq_enable_sysexit = native_irq_enable_sysexit,
+#else
+ .usersp_sysret = native_usersp_sysret,
+#endif
.iret = native_iret,
.nmi_return = native_nmi_return,
.swapgs = native_swapgs,
diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c
--- a/arch/x86/kernel/paravirt_patch_32.c
+++ b/arch/x86/kernel/paravirt_patch_32.c
@@ -8,7 +8,7 @@
DEF_NATIVE(pv_cpu_ops, iret, "iret");
DEF_NATIVE(pv_cpu_ops, nmi_return,
__stringify(NATIVE_INTERRUPT_RETURN_NMI_SAFE));
-DEF_NATIVE(pv_cpu_ops, irq_enable_syscall_ret, "sti; sysexit");
+DEF_NATIVE(pv_cpu_ops, irq_enable_sysexit, "sti; sysexit");
DEF_NATIVE(pv_mmu_ops, read_cr2, "mov %cr2, %eax");
DEF_NATIVE(pv_mmu_ops, write_cr3, "mov %eax, %cr3");
DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax");
@@ -33,7 +33,7 @@
PATCH_SITE(pv_irq_ops, save_fl);
PATCH_SITE(pv_cpu_ops, iret);
PATCH_SITE(pv_cpu_ops, nmi_return);
- PATCH_SITE(pv_cpu_ops, irq_enable_syscall_ret);
+ PATCH_SITE(pv_cpu_ops, irq_enable_sysexit);
PATCH_SITE(pv_mmu_ops, read_cr2);
PATCH_SITE(pv_mmu_ops, read_cr3);
PATCH_SITE(pv_mmu_ops, write_cr3);
diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c
--- a/arch/x86/kernel/paravirt_patch_64.c
+++ b/arch/x86/kernel/paravirt_patch_64.c
@@ -18,7 +18,7 @@
DEF_NATIVE(pv_cpu_ops, wbinvd, "wbinvd");

/* the three commands give us more control to how to return from a syscall */
-DEF_NATIVE(pv_cpu_ops, irq_enable_syscall_ret, "movq %gs:" __stringify(pda_oldrsp) ", %rsp; swapgs; sysretq;");
+DEF_NATIVE(pv_cpu_ops, usersp_sysret, "movq %gs:" __stringify(pda_oldrsp) ", %rsp; swapgs; sysretq;");
DEF_NATIVE(pv_cpu_ops, swapgs, "swapgs");

unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
@@ -39,7 +39,7 @@
PATCH_SITE(pv_irq_ops, irq_disable);
PATCH_SITE(pv_cpu_ops, iret);
PATCH_SITE(pv_cpu_ops, nmi_return);
- PATCH_SITE(pv_cpu_ops, irq_enable_syscall_ret);
+ PATCH_SITE(pv_cpu_ops, usersp_sysret);
PATCH_SITE(pv_cpu_ops, swapgs);
PATCH_SITE(pv_mmu_ops, read_cr2);
PATCH_SITE(pv_mmu_ops, read_cr3);
diff --git a/arch/x86/kernel/vmi_32.c b/arch/x86/kernel/vmi_32.c
--- a/arch/x86/kernel/vmi_32.c
+++ b/arch/x86/kernel/vmi_32.c
@@ -153,7 +153,7 @@
return patch_internal(VMI_CALL_IRET, len, insns, ip);
case PARAVIRT_PATCH(pv_cpu_ops.nmi_return):
return patch_internal(VMI_CALL_IRET, len, insns, ip);
- case PARAVIRT_PATCH(pv_cpu_ops.irq_enable_syscall_ret):
+ case PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit):
return patch_internal(VMI_CALL_SYSEXIT, len, insns, ip);
default:
break;
@@ -898,7 +898,7 @@
* the backend. They are performance critical anyway, so requiring
* a patch is not a big problem.
*/
- pv_cpu_ops.irq_enable_syscall_ret = (void *)0xfeedbab0;
+ pv_cpu_ops.irq_enable_sysexit = (void *)0xfeedbab0;
pv_cpu_ops.iret = (void *)0xbadbab0;

#ifdef CONFIG_SMP
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1087,7 +1087,7 @@

.iret = xen_iret,
.nmi_return = xen_iret,
- .irq_enable_syscall_ret = xen_sysexit,
+ .irq_enable_sysexit = xen_sysexit,

.load_tr_desc = paravirt_nop,
.set_ldt = xen_set_ldt,
diff --git a/include/asm-x86/irqflags.h b/include/asm-x86/irqflags.h
--- a/include/asm-x86/irqflags.h
+++ b/include/asm-x86/irqflags.h
@@ -168,13 +168,13 @@

#ifdef CONFIG_X86_64
#define INTERRUPT_RETURN iretq
-#define ENABLE_INTERRUPTS_SYSCALL_RET \
+#define USERSP_SYSRET \
movq %gs:pda_oldrsp, %rsp; \
swapgs; \
sysretq;
#else
#define INTERRUPT_RETURN iret
-#define ENABLE_INTERRUPTS_SYSCALL_RET sti; sysexit
+#define ENABLE_INTERRUPTS_SYSEXIT sti; sysexit
#define GET_CR0_INTO_EAX movl %cr0, %eax
#endif

diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h
--- a/include/asm-x86/paravirt.h
+++ b/include/asm-x86/paravirt.h
@@ -141,8 +141,9 @@
u64 (*read_pmc)(int counter);
unsigned long long (*read_tscp)(unsigned int *aux);

- /* These three are jmp to, not actually called. */
- void (*irq_enable_syscall_ret)(void);
+ /* These ones are jmp'ed to, not actually called. */
+ void (*irq_enable_sysexit)(void);
+ void (*usersp_sysret)(void);
void (*iret)(void);
void (*nmi_return)(void);

@@ -1485,10 +1486,10 @@
call PARA_INDIRECT(pv_irq_ops+PV_IRQ_irq_enable); \
PV_RESTORE_REGS;)

-#define ENABLE_INTERRUPTS_SYSCALL_RET \
- PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_irq_enable_syscall_ret),\
+#define ENABLE_INTERRUPTS_SYSEXIT \
+ PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_irq_enable_sysexit), \
CLBR_NONE, \
- jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_irq_enable_syscall_ret))
+ jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_irq_enable_sysexit))

#ifdef CONFIG_X86_32
@@ -1509,6 +1510,10 @@
movq %rax, %rcx; \
xorq %rax, %rax;

+#define USERSP_SYSRET \
+ PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usersp_sysret), \
+ CLBR_NONE, \
+ jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usersp_sysret))
#endif

#endif /* __ASSEMBLY__ */