[U-Boot] [PATCH 04/17] x86: Rework Global Descriptor Table loading

[Graeme Russ]

Signed-off-by: Graeme Russ <graeme.russ at gmail.com>
---
 arch/x86/cpu/cpu.c |   82 +++++++++++++++++++++++++++++++++------------------
 1 files changed, 53 insertions(+), 29 deletions(-)

diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c
index 61d0b69..bf55c26 100644
--- a/arch/x86/cpu/cpu.c
+++ b/arch/x86/cpu/cpu.c
@@ -55,35 +55,39 @@ struct gdt_ptr {
 	u32 ptr;
 } __packed;
 
-static void reload_gdt(void)
+static void load_ds(u32 segment)
 {
-	/*
-	 * There are machines which are known to not boot with the GDT
-	 * being 8-byte unaligned.  Intel recommends 16 byte alignment
-	 */
-	static const u64 boot_gdt[] __attribute__((aligned(16))) = {
-		/* CS: code, read/execute, 4 GB, base 0 */
-		[GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
-		/* DS: data, read/write, 4 GB, base 0 */
-		[GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
-		/* 16-bit CS: code, read/execute, 64 kB, base 0 */
-		[GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff),
-		/* 16-bit DS: data, read/write, 64 kB, base 0 */
-		[GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff),
-	};
-	static struct gdt_ptr gdt;
-
-	gdt.len = sizeof(boot_gdt)-1;
-	gdt.ptr = (u32)&boot_gdt;
-
-	asm volatile("lgdtl %0\n" \
-		     "movl $((2+1)*8), %%ecx\n" \
-		     "movl %%ecx, %%ds\n" \
-		     "movl %%ecx, %%es\n" \
-		     "movl %%ecx, %%fs\n" \
-		     "movl %%ecx, %%gs\n" \
-		     "movl %%ecx, %%ss" \
-		     : : "m" (gdt) : "ecx");
+	asm volatile("movl %0, %%ds" : : "r" (segment * 8));
+}
+
+static void load_es(u32 segment)
+{
+	asm volatile("movl %0, %%es" : : "r" (segment * 8));
+}
+
+static void load_fs(u32 segment)
+{
+	asm volatile("movl %0, %%fs" : : "r" (segment * 8));
+}
+
+static void load_gs(u32 segment)
+{
+	asm volatile("movl %0, %%gs" : : "r" (segment * 8));
+}
+
+static void load_ss(u32 segment)
+{
+	asm volatile("movl %0, %%ss" : : "r" (segment * 8));
+}
+
+static void load_gdt(const u64 *boot_gdt, u16 num_entries)
+{
+	struct gdt_ptr gdt;
+
+	gdt.len = (num_entries * 8) - 1;
+	gdt.ptr = (u32)boot_gdt;
+
+	asm volatile("lgdtl %0\n" : : "m" (gdt));
 }
 
 int x86_cpu_init_f(void)
@@ -113,7 +117,27 @@ int x86_cpu_init_r(void)
 	    "movl	%%eax, %%cr0\n"
 	    "wbinvd\n" : : "i" (nw_cd_rst) : "eax");
 
-	reload_gdt();
+	/*
+	 * There are machines which are known to not boot with the GDT
+	 * being 8-byte unaligned. Intel recommends 16 byte alignment
+	 */
+	static const u64 boot_gdt[] __aligned(16) = {
+		/* CS: code, read/execute, 4 GB, base 0 */
+		[GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
+		/* DS: data, read/write, 4 GB, base 0 */
+		[GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
+		/* 16-bit CS: code, read/execute, 64 kB, base 0 */
+		[GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff),
+		/* 16-bit DS: data, read/write, 64 kB, base 0 */
+		[GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff),
+	};
+
+	load_gdt(boot_gdt, GDT_NUM_ENTRIES);
+	load_ds(GDT_ENTRY_32BIT_DS);
+	load_es(GDT_ENTRY_32BIT_DS);
+	load_fs(GDT_ENTRY_32BIT_DS);
+	load_gs(GDT_ENTRY_32BIT_DS);
+	load_ss(GDT_ENTRY_32BIT_DS);
 
 	/* Initialize core interrupt and exception functionality of CPU */
 	cpu_init_interrupts();
-- 
1.7.5.2.317.g391b14