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Date: Tue, 08 Jul 2008 15:07:14 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Ingo Molnar <mingo@...e.hu>
Cc: LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
Stephen Tweedie <sct@...hat.com>,
Eduardo Habkost <ehabkost@...hat.com>,
Mark McLoughlin <markmc@...hat.com>, x86@...nel.org
Subject: [PATCH 52 of 55] xen64: set up syscall and sysenter entrypoints for
64-bit
We set up entrypoints for syscall and sysenter. sysenter is only used
for 32-bit compat processes, whereas syscall can be used in by both 32
and 64-bit processes.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
arch/x86/xen/enlighten.c | 4 +
arch/x86/xen/setup.c | 42 +++++++++++++-
arch/x86/xen/smp.c | 1
arch/x86/xen/xen-asm_64.S | 131 +++++++++++++++++++++++++++++++++++++++++++--
arch/x86/xen/xen-ops.h | 3 +
5 files changed, 175 insertions(+), 6 deletions(-)
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
@@ -1139,6 +1139,10 @@
.iret = xen_iret,
.irq_enable_sysexit = xen_sysexit,
+#ifdef CONFIG_X86_64
+ .usergs_sysret32 = xen_sysret32,
+ .usergs_sysret64 = xen_sysret64,
+#endif
.load_tr_desc = paravirt_nop,
.set_ldt = xen_set_ldt,
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -86,9 +86,11 @@
*/
static void __init fiddle_vdso(void)
{
+#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
extern const char vdso32_default_start;
u32 *mask = VDSO32_SYMBOL(&vdso32_default_start, NOTE_MASK);
*mask |= 1 << VDSO_NOTE_NONEGSEG_BIT;
+#endif
}
static __cpuinit int register_callback(unsigned type, const void *func)
@@ -106,13 +108,46 @@
{
int cpu = smp_processor_id();
extern void xen_sysenter_target(void);
+ int ret;
- if (!boot_cpu_has(X86_FEATURE_SEP) ||
- register_callback(CALLBACKTYPE_sysenter,
- xen_sysenter_target) != 0) {
+#ifdef CONFIG_X86_32
+ if (!boot_cpu_has(X86_FEATURE_SEP)) {
+ return;
+ }
+#else
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL &&
+ boot_cpu_data.x86_vendor != X86_VENDOR_CENTAUR) {
+ return;
+ }
+#endif
+
+ ret = register_callback(CALLBACKTYPE_sysenter, xen_sysenter_target);
+ if(ret != 0) {
clear_cpu_cap(&cpu_data(cpu), X86_FEATURE_SEP);
clear_cpu_cap(&boot_cpu_data, X86_FEATURE_SEP);
}
+}
+
+void __cpuinit xen_enable_syscall(void)
+{
+#ifdef CONFIG_X86_64
+ int cpu = smp_processor_id();
+ int ret;
+ extern void xen_syscall_target(void);
+ extern void xen_syscall32_target(void);
+
+ ret = register_callback(CALLBACKTYPE_syscall, xen_syscall_target);
+ if (ret != 0) {
+ printk("failed to set syscall: %d\n", ret);
+ clear_cpu_cap(&cpu_data(cpu), X86_FEATURE_SYSCALL);
+ clear_cpu_cap(&boot_cpu_data, X86_FEATURE_SYSCALL);
+ } else {
+ ret = register_callback(CALLBACKTYPE_syscall32,
+ xen_syscall32_target);
+ if (ret != 0)
+ printk("failed to set 32-bit syscall: %d\n", ret);
+ }
+#endif /* CONFIG_X86_64 */
}
void __init xen_arch_setup(void)
@@ -131,6 +166,7 @@
BUG();
xen_enable_sysenter();
+ xen_enable_syscall();
set_iopl.iopl = 1;
rc = HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -69,6 +69,7 @@
preempt_disable();
xen_enable_sysenter();
+ xen_enable_syscall();
cpu = smp_processor_id();
smp_store_cpu_info(cpu);
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -15,6 +15,8 @@
#include <asm/asm-offsets.h>
#include <asm/processor-flags.h>
+#include <asm/errno.h>
+#include <asm/segment.h>
#include <xen/interface/xen.h>
@@ -138,9 +140,132 @@
mov 8+8(%rsp),%r11
ret $16
+hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
+/*
+ Xen64 iret frame:
+
+ ss
+ rsp
+ rflags
+ cs
+ rip <-- standard iret frame
+
+ flags
+
+ rcx }
+ r11 }<-- pushed by hypercall page
+rsp -> rax }
+ */
ENTRY(xen_iret)
pushq $0
- jmp hypercall_page + __HYPERVISOR_iret * 32
+1: jmp hypercall_iret
+ENDPATCH(xen_iret)
+RELOC(xen_iret, 1b+1)
+/*
+ sysexit is not used for 64-bit processes, so it's
+ only ever used to return to 32-bit compat userspace.
+ */
ENTRY(xen_sysexit)
- ud2a
+ pushq $__USER32_DS
+ pushq %rcx
+ pushq $X86_EFLAGS_IF
+ pushq $__USER32_CS
+ pushq %rdx
+
+ pushq $VGCF_in_syscall
+1: jmp hypercall_iret
+ENDPATCH(xen_sysexit)
+RELOC(xen_sysexit, 1b+1)
+
+ENTRY(xen_sysret64)
+ /* We're already on the usermode stack at this point, but still
+ with the kernel gs, so we can easily switch back */
+ movq %rsp, %gs:pda_oldrsp
+ movq %gs:pda_kernelstack,%rsp
+
+ pushq $__USER_DS
+ pushq %gs:pda_oldrsp
+ pushq %r11
+ pushq $__USER_CS
+ pushq %rcx
+
+ pushq $VGCF_in_syscall
+1: jmp hypercall_iret
+ENDPATCH(xen_sysret64)
+RELOC(xen_sysret64, 1b+1)
+
+ENTRY(xen_sysret32)
+ /* We're already on the usermode stack at this point, but still
+ with the kernel gs, so we can easily switch back */
+ movq %rsp, %gs:pda_oldrsp
+ movq %gs:pda_kernelstack, %rsp
+
+ pushq $__USER32_DS
+ pushq %gs:pda_oldrsp
+ pushq %r11
+ pushq $__USER32_CS
+ pushq %rcx
+
+ pushq $VGCF_in_syscall
+1: jmp hypercall_iret
+ENDPATCH(xen_sysret32)
+RELOC(xen_sysret32, 1b+1)
+
+/*
+ Xen handles syscall callbacks much like ordinary exceptions,
+ which means we have:
+ - kernel gs
+ - kernel rsp
+ - an iret-like stack frame on the stack (including rcx and r11):
+ ss
+ rsp
+ rflags
+ cs
+ rip
+ r11
+ rsp-> rcx
+
+ In all the entrypoints, we undo all that to make it look
+ like a CPU-generated syscall/sysenter and jump to the normal
+ entrypoint.
+ */
+
+.macro undo_xen_syscall
+ mov 0*8(%rsp),%rcx
+ mov 1*8(%rsp),%r11
+ mov 5*8(%rsp),%rsp
+.endm
+
+/* Normal 64-bit system call target */
+ENTRY(xen_syscall_target)
+ undo_xen_syscall
+ jmp system_call_after_swapgs
+ENDPROC(xen_syscall_target)
+
+#ifdef CONFIG_IA32_EMULATION
+
+/* 32-bit compat syscall target */
+ENTRY(xen_syscall32_target)
+ undo_xen_syscall
+ jmp ia32_cstar_target
+ENDPROC(xen_syscall32_target)
+
+/* 32-bit compat sysenter target */
+ENTRY(xen_sysenter_target)
+ undo_xen_syscall
+ jmp ia32_sysenter_target
+ENDPROC(xen_sysenter_target)
+
+#else /* !CONFIG_IA32_EMULATION */
+
+ENTRY(xen_syscall32_target)
+ENTRY(xen_sysenter_target)
+ lea 16(%rsp), %rsp /* strip %rcx,%r11 */
+ mov $-ENOSYS, %rax
+ pushq $VGCF_in_syscall
+ jmp hypercall_iret
+ENDPROC(xen_syscall32_target)
+ENDPROC(xen_sysenter_target)
+
+#endif /* CONFIG_IA32_EMULATION */
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -26,6 +26,7 @@
void __init xen_arch_setup(void);
void __init xen_init_IRQ(void);
void xen_enable_sysenter(void);
+void xen_enable_syscall(void);
void xen_vcpu_restore(void);
void __init xen_build_dynamic_phys_to_machine(void);
@@ -70,6 +71,8 @@
/* These are not functions, and cannot be called normally */
void xen_iret(void);
void xen_sysexit(void);
+void xen_sysret32(void);
+void xen_sysret64(void);
void xen_adjust_exception_frame(void);
#endif /* XEN_OPS_H */
--
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