[Xen-devel] [PATCH v2 01/10] x86/traps: Mnemonics for system descriptor types

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Avoids some particularly obscure magic numbers

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>

---
v2:
 * DESC_TYPE_xxx -> SYS_DESC_xxx
 * Drop paretheses
 * Style tweaks while changing code
---
 xen/arch/x86/crash.c        |    3 ++-
 xen/arch/x86/traps.c        |    8 ++++----
 xen/arch/x86/x86_64/traps.c |   10 ++++------
 xen/include/asm-x86/desc.h  |    8 ++++++++
 xen/include/asm-x86/ldt.h   |    2 +-
 5 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/xen/arch/x86/crash.c b/xen/arch/x86/crash.c
index aed3b3e..c0b83df 100644
--- a/xen/arch/x86/crash.c
+++ b/xen/arch/x86/crash.c
@@ -149,7 +149,8 @@ static void nmi_shootdown_cpus(void)
              * This update is safe from a security point of view, as this pcpu 
              * is never going to try to sysret back to a PV vcpu.
              */
-            _set_gate_lower(&idt_tables[i][TRAP_nmi], 14, 0, &trap_nop);
+            _set_gate_lower(&idt_tables[i][TRAP_nmi],
+                            SYS_DESC_irq_gate, 0, &trap_nop);
             set_ist(&idt_tables[i][TRAP_machine_check], IST_NONE);
         }
         else
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 2cb3174..46cb48e 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -3431,8 +3431,8 @@ static void __set_intr_gate(unsigned int n, uint32_t dpl, 
void *addr)
     /* Keep secondary tables in sync with IRQ updates. */
     for ( i = 1; i < nr_cpu_ids; i++ )
         if ( idt_tables[i] != NULL )
-            _set_gate(&idt_tables[i][n], 14, dpl, addr);
-    _set_gate(&idt_table[n], 14, dpl, addr);
+            _set_gate(&idt_tables[i][n], SYS_DESC_irq_gate, dpl, addr);
+    _set_gate(&idt_table[n], SYS_DESC_irq_gate, dpl, addr);
 }
 
 static void set_swint_gate(unsigned int n, void *addr)
@@ -3457,12 +3457,12 @@ void load_TR(void)
         this_cpu(gdt_table) + TSS_ENTRY - FIRST_RESERVED_GDT_ENTRY,
         (unsigned long)tss,
         offsetof(struct tss_struct, __cacheline_filler) - 1,
-        9);
+        SYS_DESC_tss_avail);
     _set_tssldt_desc(
         this_cpu(compat_gdt_table) + TSS_ENTRY - FIRST_RESERVED_GDT_ENTRY,
         (unsigned long)tss,
         offsetof(struct tss_struct, __cacheline_filler) - 1,
-        11);
+        SYS_DESC_tss_busy);
 
     /* Switch to non-compat GDT (which has B bit clear) to execute LTR. */
     asm volatile (
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index 3a48478..8328a2c 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -390,14 +390,12 @@ void __devinit subarch_percpu_traps_init(void)
         set_ist(&idt_table[TRAP_nmi],           IST_NMI);
         set_ist(&idt_table[TRAP_machine_check], IST_MCE);
 
-        /*
-         * The 32-on-64 hypercall entry vector is only accessible from ring 1.
-         * Also note that this is a trap gate, not an interrupt gate.
-         */
-        _set_gate(idt_table+HYPERCALL_VECTOR, 15, 1, &compat_hypercall);
+        /* The 32-on-64 hypercall vector is only accessible from ring 1. */
+        _set_gate(idt_table + HYPERCALL_VECTOR,
+                  SYS_DESC_trap_gate, 1, &compat_hypercall);
 
         /* Fast trap for int80 (faster than taking the #GP-fixup path). */
-        _set_gate(idt_table+0x80, 15, 3, &int80_direct_trap);
+        _set_gate(idt_table + 0x80, SYS_DESC_trap_gate, 3, &int80_direct_trap);
     }
 
     stack_bottom = (char *)get_stack_bottom();
diff --git a/xen/include/asm-x86/desc.h b/xen/include/asm-x86/desc.h
index 4edb834..8257167 100644
--- a/xen/include/asm-x86/desc.h
+++ b/xen/include/asm-x86/desc.h
@@ -98,6 +98,14 @@
 
 #ifndef __ASSEMBLY__
 
+/* System Descriptor types for GDT and IDT entries. */
+#define SYS_DESC_ldt          2
+#define SYS_DESC_tss_avail    9
+#define SYS_DESC_tss_busy     11
+#define SYS_DESC_call_gate    12
+#define SYS_DESC_irq_gate     14
+#define SYS_DESC_trap_gate    15
+
 struct desc_struct {
     u32 a, b;
 };
diff --git a/xen/include/asm-x86/ldt.h b/xen/include/asm-x86/ldt.h
index b6f7beb..aa77368 100644
--- a/xen/include/asm-x86/ldt.h
+++ b/xen/include/asm-x86/ldt.h
@@ -18,7 +18,7 @@ static inline void load_LDT(struct vcpu *v)
         desc = (!is_pv_32on64_vcpu(v)
                 ? this_cpu(gdt_table) : this_cpu(compat_gdt_table))
                + LDT_ENTRY - FIRST_RESERVED_GDT_ENTRY;
-        _set_tssldt_desc(desc, LDT_VIRT_START(v), ents*8-1, 2);
+        _set_tssldt_desc(desc, LDT_VIRT_START(v), ents*8-1, SYS_DESC_ldt);
         __asm__ __volatile__ ( "lldt %%ax" : : "a" (LDT_ENTRY << 3) );
     }
 }
-- 
1.7.10.4


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