x86/paravirt: add sysret/sysexit pvops for returning to 32-bit compatibility userspace
In a 64-bit system, we need separate sysret/sysexit operations to
return to a 32-bit userspace.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citirx.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 3aefbce..2a4c424 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -61,6 +61,19 @@
CFI_UNDEFINED r15
.endm
+#ifdef CONFIG_PARAVIRT
+ENTRY(native_usergs_sysret32)
+ swapgs
+ sysretl
+ENDPROC(native_usergs_sysret32)
+
+ENTRY(native_irq_enable_sysexit)
+ swapgs
+ sti
+ sysexit
+ENDPROC(native_irq_enable_sysexit)
+#endif
+
/*
* 32bit SYSENTER instruction entry.
*
@@ -151,10 +164,7 @@
CFI_ADJUST_CFA_OFFSET -8
CFI_REGISTER rsp,rcx
TRACE_IRQS_ON
- swapgs
- sti /* sti only takes effect after the next instruction */
- /* sysexit */
- .byte 0xf, 0x35
+ ENABLE_INTERRUPTS_SYSEXIT32
sysenter_tracesys:
CFI_RESTORE_STATE
@@ -254,8 +264,7 @@
TRACE_IRQS_ON
movl RSP-ARGOFFSET(%rsp),%esp
CFI_RESTORE rsp
- swapgs
- sysretl
+ USERGS_SYSRET32
cstar_tracesys:
CFI_RESTORE_STATE
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index a19aba8..06c451a 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -62,7 +62,9 @@
OFFSET(PV_IRQ_irq_disable, pv_irq_ops, irq_disable);
OFFSET(PV_IRQ_irq_enable, pv_irq_ops, irq_enable);
OFFSET(PV_CPU_iret, pv_cpu_ops, iret);
- OFFSET(PV_CPU_usergs_sysret, pv_cpu_ops, usergs_sysret);
+ OFFSET(PV_CPU_usergs_sysret32, pv_cpu_ops, usergs_sysret32);
+ OFFSET(PV_CPU_usergs_sysret64, pv_cpu_ops, usergs_sysret64);
+ OFFSET(PV_CPU_irq_enable_sysexit, pv_cpu_ops, irq_enable_sysexit);
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_64.S b/arch/x86/kernel/entry_64.S
index 18447a3..880ffe5 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -59,7 +59,7 @@
#endif
#ifdef CONFIG_PARAVIRT
-ENTRY(native_usergs_sysret)
+ENTRY(native_usergs_sysret64)
swapgs
sysretq
#endif /* CONFIG_PARAVIRT */
@@ -275,7 +275,7 @@
RESTORE_ARGS 0,-ARG_SKIP,1
/*CFI_REGISTER rflags,r11*/
movq %gs:pda_oldrsp, %rsp
- USERGS_SYSRET
+ USERGS_SYSRET64
CFI_RESTORE_STATE
/* Handle reschedules */
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index b0b17f0..bf1067e 100644
--- 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.irq_enable_sysexit) ||
- type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret))
+ type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret32) ||
+ type == PARAVIRT_PATCH(pv_cpu_ops.usergs_sysret64))
/* 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_irq_enable_sysexit(void);
-extern void native_usergs_sysret(void);
+extern void native_usergs_sysret32(void);
+extern void native_usergs_sysret64(void);
static int __init print_banner(void)
{
@@ -329,10 +331,10 @@
.write_idt_entry = native_write_idt_entry,
.load_sp0 = native_load_sp0,
-#ifdef CONFIG_X86_32
.irq_enable_sysexit = native_irq_enable_sysexit,
-#else
- .usergs_sysret = native_usergs_sysret,
+#ifdef CONFIG_X86_64
+ .usergs_sysret32 = native_usergs_sysret32,
+ .usergs_sysret64 = native_usergs_sysret64,
#endif
.iret = native_iret,
.swapgs = native_swapgs,
diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c
index d4c0712..061d01d 100644
--- a/arch/x86/kernel/paravirt_patch_64.c
+++ b/arch/x86/kernel/paravirt_patch_64.c
@@ -14,8 +14,9 @@
DEF_NATIVE(pv_cpu_ops, clts, "clts");
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, usergs_sysret, "swapgs; sysretq;");
+DEF_NATIVE(pv_cpu_ops, irq_enable_sysexit, "swapgs; sti; sysexit");
+DEF_NATIVE(pv_cpu_ops, usergs_sysret64, "swapgs; sysretq");
+DEF_NATIVE(pv_cpu_ops, usergs_sysret32, "swapgs; sysretl");
DEF_NATIVE(pv_cpu_ops, swapgs, "swapgs");
unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
@@ -35,7 +36,9 @@
PATCH_SITE(pv_irq_ops, irq_enable);
PATCH_SITE(pv_irq_ops, irq_disable);
PATCH_SITE(pv_cpu_ops, iret);
- PATCH_SITE(pv_cpu_ops, usergs_sysret);
+ PATCH_SITE(pv_cpu_ops, irq_enable_sysexit);
+ PATCH_SITE(pv_cpu_ops, usergs_sysret32);
+ PATCH_SITE(pv_cpu_ops, usergs_sysret64);
PATCH_SITE(pv_cpu_ops, swapgs);
PATCH_SITE(pv_mmu_ops, read_cr2);
PATCH_SITE(pv_mmu_ops, read_cr3);
diff --git a/include/asm-x86/irqflags.h b/include/asm-x86/irqflags.h
index 544836c..ea9bd26 100644
--- a/include/asm-x86/irqflags.h
+++ b/include/asm-x86/irqflags.h
@@ -112,9 +112,17 @@
#ifdef CONFIG_X86_64
#define INTERRUPT_RETURN iretq
-#define USERGS_SYSRET \
- swapgs; \
- sysretq;
+#define USERGS_SYSRET64 \
+ swapgs; \
+ sysretq;
+#define USERGS_SYSRET32 \
+ swapgs; \
+ sysretl
+#define ENABLE_INTERRUPTS_SYSEXIT32 \
+ swapgs; \
+ sti; \
+ sysexit
+
#else
#define INTERRUPT_RETURN iret
#define ENABLE_INTERRUPTS_SYSEXIT sti; sysexit
diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h
index dad5b41..33f72f8 100644
--- a/include/asm-x86/paravirt.h
+++ b/include/asm-x86/paravirt.h
@@ -141,9 +141,32 @@
u64 (*read_pmc)(int counter);
unsigned long long (*read_tscp)(unsigned int *aux);
- /* These three are jmp to, not actually called. */
+ /*
+ * Atomically enable interrupts and return to userspace. This
+ * is only ever used to return to 32-bit processes; in a
+ * 64-bit kernel, it's used for 32-on-64 compat processes, but
+ * never native 64-bit processes. (Jump, not call.)
+ */
void (*irq_enable_sysexit)(void);
- void (*usergs_sysret)(void);
+
+ /*
+ * Switch to usermode gs and return to 64-bit usermode using
+ * sysret. Only used in 64-bit kernels to return to 64-bit
+ * processes. Usermode register state, including %rsp, must
+ * already be restored.
+ */
+ void (*usergs_sysret64)(void);
+
+ /*
+ * Switch to usermode gs and return to 32-bit usermode using
+ * sysret. Used to return to 32-on-64 compat processes.
+ * Other usermode register state, including %esp, must already
+ * be restored.
+ */
+ void (*usergs_sysret32)(void);
+
+ /* Normal iret. Jump to this with the standard iret stack
+ frame set up. */
void (*iret)(void);
void (*swapgs)(void);
@@ -1481,18 +1504,24 @@
call PARA_INDIRECT(pv_irq_ops+PV_IRQ_irq_enable); \
PV_RESTORE_REGS;)
-#define ENABLE_INTERRUPTS_SYSEXIT \
- PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_irq_enable_sysexit), \
+#define USERGS_SYSRET32 \
+ PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret32), \
CLBR_NONE, \
- jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_irq_enable_sysexit))
-
+ jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usergs_sysret32))
#ifdef CONFIG_X86_32
#define GET_CR0_INTO_EAX \
push %ecx; push %edx; \
call PARA_INDIRECT(pv_cpu_ops+PV_CPU_read_cr0); \
pop %edx; pop %ecx
-#else
+
+#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_sysexit))
+
+
+#else /* !CONFIG_X86_32 */
#define SWAPGS \
PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_swapgs), CLBR_NONE, \
PV_SAVE_REGS; \
@@ -1505,11 +1534,16 @@
movq %rax, %rcx; \
xorq %rax, %rax;
-#define USERGS_SYSRET \
- PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret), \
+#define USERGS_SYSRET64 \
+ PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret64), \
CLBR_NONE, \
- jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usergs_sysret))
-#endif
+ jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usergs_sysret64))
+
+#define ENABLE_INTERRUPTS_SYSEXIT32 \
+ PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_irq_enable_sysexit), \
+ CLBR_NONE, \
+ jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_irq_enable_sysexit))
+#endif /* CONFIG_X86_32 */
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_PARAVIRT */
