From 9ea03e01a0ef2fa4cf62b7ab4de52d76db979e2a Mon Sep 17 00:00:00 2001
From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Thu, 24 Dec 2015 21:04:27 +0000
Subject: [PATCH] Setup for common PV userspace execution

* Implement and use hypercall_stack_switch().
* Implement {read,write}_[cdefgs]s() wrappers.
* Use __USER_DS for the regular data segment selectors.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 arch/x86/pv/traps.c     | 11 ++++++
 include/arch/x86/lib.h  | 79 +++++++++++++++++++++++++++++++++++++++++
 include/xtf/hypercall.h |  5 +++
 3 files changed, 95 insertions(+)

diff --git a/arch/x86/pv/traps.c b/arch/x86/pv/traps.c
index fda8285..3612872 100644
--- a/arch/x86/pv/traps.c
+++ b/arch/x86/pv/traps.c
@@ -52,10 +52,21 @@ struct xen_trap_info pv_default_trap_info[] =
 
 void arch_init_traps(void)
 {
+    /* PV equivalent of `lidt`. */
     int rc = hypercall_set_trap_table(pv_default_trap_info);
 
     if ( rc )
         panic("Failed to set trap table: %d\n", rc);
+
+    /* PV equivalent of setting tss.{esp0,ss0}. */
+    rc = hypercall_stack_switch(__KERN_DS, &boot_stack[2 * PAGE_SIZE]);
+    if ( rc )
+        panic("Failed to set kernel stack: %d\n", rc);
+
+    write_ds(__USER_DS);
+    write_es(__USER_DS);
+    write_fs(__USER_DS);
+    write_gs(__USER_DS);
 }
 
 void __noreturn arch_crash_hard(void)
diff --git a/include/arch/x86/lib.h b/include/arch/x86/lib.h
index 458e25f..7951695 100644
--- a/include/arch/x86/lib.h
+++ b/include/arch/x86/lib.h
@@ -79,6 +79,85 @@ static inline void outl(uint32_t val, uint16_t port)
     asm volatile("outl %k0, %w1": : "a" (val), "Nd" (port));
 }
 
+static inline unsigned int read_cs(void)
+{
+    unsigned int cs;
+
+    asm volatile ("mov %%cs, %0" : "=r" (cs));
+
+    return cs;
+}
+
+static inline unsigned int read_ds(void)
+{
+    unsigned int ds;
+
+    asm volatile ("mov %%ds, %0" : "=r" (ds));
+
+    return ds;
+}
+
+static inline unsigned int read_es(void)
+{
+    unsigned int es;
+
+    asm volatile ("mov %%es, %0" : "=r" (es));
+
+    return es;
+}
+
+static inline unsigned int read_fs(void)
+{
+    unsigned int fs;
+
+    asm volatile ("mov %%fs, %0" : "=r" (fs));
+
+    return fs;
+}
+
+static inline unsigned int read_gs(void)
+{
+    unsigned int gs;
+
+    asm volatile ("mov %%gs, %0" : "=r" (gs));
+
+    return gs;
+}
+
+static inline unsigned int read_ss(void)
+{
+    unsigned int ss;
+
+    asm volatile ("mov %%ss, %0" : "=r" (ss));
+
+    return ss;
+}
+
+static inline void write_ds(unsigned int ds)
+{
+    asm volatile ("mov %0, %%ds" :: "r" (ds));
+}
+
+static inline void write_es(unsigned int es)
+{
+    asm volatile ("mov %0, %%es" :: "r" (es));
+}
+
+static inline void write_fs(unsigned int fs)
+{
+    asm volatile ("mov %0, %%fs" :: "r" (fs));
+}
+
+static inline void write_gs(unsigned int gs)
+{
+    asm volatile ("mov %0, %%gs" :: "r" (gs));
+}
+
+static inline void write_ss(unsigned int ss)
+{
+    asm volatile ("mov %0, %%ss" :: "r" (ss));
+}
+
 static inline unsigned long read_dr6(void)
 {
     unsigned long val;
diff --git a/include/xtf/hypercall.h b/include/xtf/hypercall.h
index 124ff6a..7e3bded 100644
--- a/include/xtf/hypercall.h
+++ b/include/xtf/hypercall.h
@@ -39,6 +39,11 @@ static inline long hypercall_set_trap_table(const struct xen_trap_info *ti)
     return HYPERCALL1(long, __HYPERVISOR_set_trap_table, ti);
 }
 
+static inline long hypercall_stack_switch(const unsigned int ss, const void *sp)
+{
+    return HYPERCALL2(long, __HYPERVISOR_stack_switch, ss, sp);
+}
+
 static inline long hypercall_sched_op(unsigned int cmd, void *arg)
 {
     return HYPERCALL2(long, __HYPERVISOR_sched_op, cmd, arg);
-- 
2.39.5