[kvm-unit-tests PATCH v2 2/3] x86: Make set_gdt_entry usable in 64-bit mode

[Jim Mattson <jmattson@xxxxxxxxxx>]

The omission of a 64-bit implementation of set_gdt_entry was probably
just an oversight, since the declaration is in scope.

Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
---
 lib/x86/desc.c | 41 +++++++++++++++++++++++++++++++----------
 lib/x86/desc.h |  3 ++-
 x86/cstart64.S |  1 +
 3 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/lib/x86/desc.c b/lib/x86/desc.c
index e7378c1d372a..87e2850f46c6 100644
--- a/lib/x86/desc.c
+++ b/lib/x86/desc.c
@@ -279,23 +279,39 @@ bool exception_rflags_rf(void)
 
 static char intr_alt_stack[4096];
 
-#ifndef __x86_64__
-void set_gdt_entry(int sel, u32 base,  u32 limit, u8 access, u8 gran)
+static void __set_gdt_entry(int sel, uintptr_t base, u32 limit, u8 access,
+			    u8 gran, gdt_entry_t *gdt)
 {
 	int num = sel >> 3;
 
 	/* Setup the descriptor base address */
-	gdt32[num].base_low = (base & 0xFFFF);
-	gdt32[num].base_middle = (base >> 16) & 0xFF;
-	gdt32[num].base_high = (base >> 24) & 0xFF;
+	gdt[num].base_low = (base & 0xFFFF);
+	gdt[num].base_middle = (base >> 16) & 0xFF;
+	gdt[num].base_high = (base >> 24) & 0xFF;
 
 	/* Setup the descriptor limits */
-	gdt32[num].limit_low = (limit & 0xFFFF);
-	gdt32[num].granularity = ((limit >> 16) & 0x0F);
+	gdt[num].limit_low = (limit & 0xFFFF);
+	gdt[num].granularity = ((limit >> 16) & 0x0F);
+
+	/* Penultimately, set up the granularity and access flags */
+	gdt[num].granularity |= (gran & 0xF0);
+	gdt[num].access = access;
+
+#ifdef __x86_64__
+	/* 64-bit system descriptors take up two slots */
+	if (!(access & 0x10000)) {
+		u32 *p = (u32 *)&gdt[num + 1];
 
-	/* Finally, set up the granularity and access flags */
-	gdt32[num].granularity |= (gran & 0xF0);
-	gdt32[num].access = access;
+		p[0] = base >> 32;
+		p[1] = 0;
+	}
+#endif
+}
+
+#ifndef __x86_64__
+void set_gdt_entry(int sel, uintptr_t base, u32 limit, u8 access, u8 gran)
+{
+	__set_gdt_entry(sel, base, limit, access, gran, gdt32);
 }
 
 void set_gdt_task_gate(u16 sel, u16 tss_sel)
@@ -366,6 +382,11 @@ void print_current_tss_info(void)
 		       tr, tr ? "interrupt" : "main", tss.prev, tss_intr.prev);
 }
 #else
+void set_gdt_entry(int sel, uintptr_t base, u32 limit, u8 access, u8 gran)
+{
+	__set_gdt_entry(sel, base, limit, access, gran, gdt64);
+}
+
 void set_intr_alt_stack(int e, void *addr)
 {
 	set_idt_entry(e, addr, 0);
diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index a6ffb38c79a1..994f1d791130 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -208,6 +208,7 @@ void set_idt_task_gate(int vec, u16 sel);
 void set_intr_task_gate(int vec, void *fn);
 void setup_tss32(void);
 #else
+extern gdt_entry_t gdt64[];
 extern tss64_t tss;
 #endif
 
@@ -218,7 +219,7 @@ bool exception_rflags_rf(void);
 void set_idt_entry(int vec, void *addr, int dpl);
 void set_idt_sel(int vec, u16 sel);
 void set_idt_dpl(int vec, u16 dpl);
-void set_gdt_entry(int sel, u32 base,  u32 limit, u8 access, u8 gran);
+void set_gdt_entry(int sel, uintptr_t base,  u32 limit, u8 access, u8 gran);
 void set_intr_alt_stack(int e, void *fn);
 void print_current_tss_info(void);
 handler handle_exception(u8 v, handler fn);
diff --git a/x86/cstart64.S b/x86/cstart64.S
index 5c6ad38543cc..62ace3512bb0 100644
--- a/x86/cstart64.S
+++ b/x86/cstart64.S
@@ -62,6 +62,7 @@ gdt64_desc:
 	.word gdt64_end - gdt64 - 1
 	.quad gdt64
 
+.globl gdt64
 gdt64:
 	.quad 0
 	.quad 0x00af9b000000ffff // 64-bit code segment
-- 
2.33.0.1079.g6e70778dc9-goog