From 74bfbe1ba5ba99adccdc26dc4adbfb9221849310 Mon Sep 17 00:00:00 2001 From: Graeme Russ Date: Thu, 29 Dec 2011 21:45:33 +1100 Subject: [PATCH] x86: Rework Global Descriptor Table loading The inline assembler is ugly and uses hard coded magic numbers. Make it more elegant to allow cleaner implementation of future GDT related patches. The compiler seems smart enough to generate the same code anyway -- Changes for v2: - Rebased against revised patch #3 - Use GDT size define instead of magic number - Added commit message --- arch/x86/cpu/cpu.c | 82 ++++++++++++++++++++++++++++++---------------- 1 file changed, 53 insertions(+), 29 deletions(-) diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c index 209ff2989b..8102fb9519 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 */ - [X86_GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff), - /* DS: data, read/write, 4 GB, base 0 */ - [X86_GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff), - /* 16-bit CS: code, read/execute, 64 kB, base 0 */ - [X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff), - /* 16-bit DS: data, read/write, 64 kB, base 0 */ - [X86_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 * X86_GDT_ENTRY_SIZE)); +} + +static void load_es(u32 segment) +{ + asm volatile("movl %0, %%es" : : "r" (segment * X86_GDT_ENTRY_SIZE)); +} + +static void load_fs(u32 segment) +{ + asm volatile("movl %0, %%fs" : : "r" (segment * X86_GDT_ENTRY_SIZE)); +} + +static void load_gs(u32 segment) +{ + asm volatile("movl %0, %%gs" : : "r" (segment * X86_GDT_ENTRY_SIZE)); +} + +static void load_ss(u32 segment) +{ + asm volatile("movl %0, %%ss" : : "r" (segment * X86_GDT_ENTRY_SIZE)); +} + +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 */ + [X86_GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff), + /* DS: data, read/write, 4 GB, base 0 */ + [X86_GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff), + /* 16-bit CS: code, read/execute, 64 kB, base 0 */ + [X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff), + /* 16-bit DS: data, read/write, 64 kB, base 0 */ + [X86_GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff), + }; + + load_gdt(boot_gdt, X86_GDT_NUM_ENTRIES); + load_ds(X86_GDT_ENTRY_32BIT_DS); + load_es(X86_GDT_ENTRY_32BIT_DS); + load_fs(X86_GDT_ENTRY_32BIT_DS); + load_gs(X86_GDT_ENTRY_32BIT_DS); + load_ss(X86_GDT_ENTRY_32BIT_DS); /* Initialize core interrupt and exception functionality of CPU */ cpu_init_interrupts(); -- 2.39.5