[U-Boot] [PATCH 07/17] x86: Use fs for global data
Simon Glass
sjg at chromium.org
Wed Jan 4 06:36:17 CET 2012
Hi Graeme,
On Sun, Jan 1, 2012 at 8:09 PM, Graeme Russ <graeme.russ at gmail.com> wrote:
> Use the base address of the 'F' segment as a pointer to the global data
> structure. By adding the linear address (i.e. the 'D' segment address)
> as the first word of the global data structure, the address of the
> global data relative to the 'D' segment can be found simply, for
> example, by:
>
> fs movl 0, %eax
>
> This makes the gd 'pointer' writable prior to relocation (by reloading
> the GDT) which brings x86 into line with all other arches
What is the GDT?
>
> NOTE: Writing to the gd 'pointer' is expensive (but we only do it
> twice) but using it to access global data members (read and write) is
> still fairly cheap
>
> Signed-off-by: Graeme Russ <graeme.russ at gmail.com>
> ---
> arch/x86/cpu/cpu.c | 53 ++++++++++++++++++++--------------
> arch/x86/cpu/start.S | 8 ++++-
> arch/x86/include/asm/global_data.h | 21 +++++++++----
> arch/x86/include/asm/processor.h | 6 +++-
> arch/x86/include/asm/u-boot-x86.h | 2 +
> arch/x86/lib/board.c | 56 +++++++++++++++++++++++++-----------
> 6 files changed, 98 insertions(+), 48 deletions(-)
>
> diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c
> index bf55c26..e7a5fc0 100644
> --- a/arch/x86/cpu/cpu.c
> +++ b/arch/x86/cpu/cpu.c
> @@ -90,6 +90,37 @@ static void load_gdt(const u64 *boot_gdt, u16 num_entries)
> asm volatile("lgdtl %0\n" : : "m" (gdt));
> }
>
> +void init_gd(gd_t *id, u64 *gdt_addr)
> +{
> + id->gd_addr = (ulong)id;
> + setup_gdt(id, gdt_addr);
> +}
> +
> +void setup_gdt(gd_t *id, u64 *gdt_addr)
I will probably never understand this function but a comment might be nice.
> +{
> + /* CS: code, read/execute, 4 GB, base 0 */
> + gdt_addr[GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff);
> +
> + /* DS: data, read/write, 4 GB, base 0 */
> + gdt_addr[GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff);
> +
> + /* FS: data, read/write, 4 GB, base (Global Data Pointer) */
> + gdt_addr[GDT_ENTRY_32BIT_FS] = GDT_ENTRY(0xc093, (ulong)id, 0xfffff);
> +
> + /* 16-bit CS: code, read/execute, 64 kB, base 0 */
Extra indent?
> + gdt_addr[GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff);
> +
> + /* 16-bit DS: data, read/write, 64 kB, base 0 */
> + gdt_addr[GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff);
> +
> + load_gdt(gdt_addr, GDT_NUM_ENTRIES);
> + load_ds(GDT_ENTRY_32BIT_DS);
> + load_es(GDT_ENTRY_32BIT_DS);
> + load_gs(GDT_ENTRY_32BIT_DS);
> + load_ss(GDT_ENTRY_32BIT_DS);
> + load_fs(GDT_ENTRY_32BIT_FS);
> +}
> +
> int x86_cpu_init_f(void)
> {
> const u32 em_rst = ~X86_CR0_EM;
> @@ -117,28 +148,6 @@ int x86_cpu_init_r(void)
> "movl %%eax, %%cr0\n"
> "wbinvd\n" : : "i" (nw_cd_rst) : "eax");
>
> - /*
> - * 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();
> return 0;
> diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S
> index 9592158..4fb9e6b 100644
> --- a/arch/x86/cpu/start.S
> +++ b/arch/x86/cpu/start.S
> @@ -31,7 +31,7 @@
> #include <asm/global_data.h>
> #include <asm/processor.h>
> #include <asm/processor-flags.h>
> -#include <generated/asm-offsets.h>
> +#include <generated/generic-asm-offsets.h>
>
> .section .text
> .code32
> @@ -85,6 +85,12 @@ car_init_ret:
> */
> movl $CONFIG_SYS_INIT_SP_ADDR, %esp
>
> + /* Initialise the Global Data Pointer */
> + movl $CONFIG_SYS_INIT_GD_ADDR, %eax
> + movl %eax, %edx
> + addl $GENERATED_GBL_DATA_SIZE, %edx
> + call init_gd;
> +
> /* Set parameter to board_init_f() to boot flags */
> xorl %eax, %eax
> movw %bx, %ax
> diff --git a/arch/x86/include/asm/global_data.h b/arch/x86/include/asm/global_data.h
> index 05a2139..908a02c 100644
> --- a/arch/x86/include/asm/global_data.h
> +++ b/arch/x86/include/asm/global_data.h
> @@ -36,6 +36,8 @@
> #ifndef __ASSEMBLY__
>
> typedef struct global_data {
> + /* NOTE: gd_addr MUST be first member of struct global_data! */
> + unsigned long gd_addr; /* Location of Global Data */
> bd_t *bd;
> unsigned long flags;
> unsigned long baudrate;
> @@ -51,13 +53,24 @@ typedef struct global_data {
> unsigned long bus_clk;
> unsigned long relocaddr; /* Start address of U-Boot in RAM */
> unsigned long start_addr_sp; /* start_addr_stackpointer */
> + unsigned long gdt_addr; /* Location of GDT */
> + unsigned long new_gd_addr; /* New location of Global Data */
> phys_size_t ram_size; /* RAM size */
> unsigned long reset_status; /* reset status register at boot */
> void **jt; /* jump table */
> char env_buf[32]; /* buffer for getenv() before reloc. */
> } gd_t;
>
> -extern gd_t *gd;
> +static inline gd_t *get_fs_gd_ptr(void)
> +{
> + gd_t *gd_ptr;
> +
> + asm volatile("fs movl 0, %0\n" : "=r" (gd_ptr));
> +
> + return gd_ptr;
> +}
> +
> +#define gd get_fs_gd_ptr()
>
> #endif
>
> @@ -73,12 +86,6 @@ extern gd_t *gd;
> #define GD_FLG_DISABLE_CONSOLE 0x00040 /* Disable console (in & out) */
> #define GD_FLG_ENV_READY 0x00080 /* Environment imported into hash table */
>
> -#if 0
> #define DECLARE_GLOBAL_DATA_PTR
> -#else
> -#define XTRN_DECLARE_GLOBAL_DATA_PTR extern
> -#define DECLARE_GLOBAL_DATA_PTR XTRN_DECLARE_GLOBAL_DATA_PTR \
> -gd_t *gd
> -#endif
>
> #endif /* __ASM_GBL_DATA_H */
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 203c63a..07897f9 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -24,13 +24,17 @@
> #ifndef __ASM_PROCESSOR_H_
> #define __ASM_PROCESSOR_H_ 1
>
> +#define GDT_ENTRY_SIZE 8
> +
> #define GDT_ENTRY_NULL 0
> #define GDT_ENTRY_UNUSED (GDT_ENTRY_NULL + 1)
> #define GDT_ENTRY_32BIT_CS (GDT_ENTRY_UNUSED + 1)
> #define GDT_ENTRY_32BIT_DS (GDT_ENTRY_32BIT_CS + 1)
> -#define GDT_ENTRY_16BIT_CS (GDT_ENTRY_32BIT_DS + 1)
> +#define GDT_ENTRY_32BIT_FS (GDT_ENTRY_32BIT_DS + 1)
> +#define GDT_ENTRY_16BIT_CS (GDT_ENTRY_32BIT_FS + 1)
> #define GDT_ENTRY_16BIT_DS (GDT_ENTRY_16BIT_CS + 1)
>
> #define GDT_NUM_ENTRIES (GDT_ENTRY_16BIT_DS + 1)
> +#define GDT_SIZE (GDT_NUM_ENTRIES * GDT_ENTRY_SIZE)
Wasn't this already done in an earlier patch?
>
> #endif
> diff --git a/arch/x86/include/asm/u-boot-x86.h b/arch/x86/include/asm/u-boot-x86.h
> index c3d2277..5540d51 100644
> --- a/arch/x86/include/asm/u-boot-x86.h
> +++ b/arch/x86/include/asm/u-boot-x86.h
> @@ -37,6 +37,8 @@ int x86_cpu_init_r(void);
> int cpu_init_r(void);
> int x86_cpu_init_f(void);
> int cpu_init_f(void);
> +void init_gd(gd_t *id, u64 *gdt_addr);
> +void setup_gdt(gd_t *id, u64 *gdt_addr);
>
> /* cpu/.../timer.c */
> void timer_isr(void *);
> diff --git a/arch/x86/lib/board.c b/arch/x86/lib/board.c
> index bc5027b..9c4ecda 100644
> --- a/arch/x86/lib/board.c
> +++ b/arch/x86/lib/board.c
> @@ -42,20 +42,12 @@
> #include <serial.h>
> #include <asm/u-boot-x86.h>
> #include <elf.h>
> +#include <asm/processor.h>
>
> #ifdef CONFIG_BITBANGMII
> #include <miiphy.h>
> #endif
>
> -/*
> - * Pointer to initial global data area
> - *
> - * Here we initialize it.
> - */
> -#undef XTRN_DECLARE_GLOBAL_DATA_PTR
> -#define XTRN_DECLARE_GLOBAL_DATA_PTR /* empty = allocate here */
> -DECLARE_GLOBAL_DATA_PTR = (gd_t *) (CONFIG_SYS_INIT_GD_ADDR);
> -
> /************************************************************************
> * Init Utilities *
> ************************************************************************
> @@ -128,6 +120,7 @@ static int calculate_relocation_address(void);
> static int copy_uboot_to_ram(void);
> static int clear_bss(void);
> static int do_elf_reloc_fixups(void);
> +static int copy_gd_to_ram(void);
>
> init_fnc_t *init_sequence_f[] = {
> cpu_init_f,
> @@ -146,6 +139,7 @@ init_fnc_t *init_sequence_f[] = {
> };
>
> init_fnc_t *init_sequence_r[] = {
> + copy_gd_to_ram,
> cpu_init_r, /* basic cpu dependent setup */
> board_early_init_r, /* basic board dependent setup */
> dram_init, /* configure available RAM banks */
> @@ -157,8 +151,6 @@ init_fnc_t *init_sequence_r[] = {
> NULL,
> };
>
> -gd_t *gd;
> -
> static int calculate_relocation_address(void)
> {
> ulong text_start = (ulong)&__text_start;
> @@ -171,8 +163,18 @@ static int calculate_relocation_address(void)
> * requirements
> */
>
> - /* Stack is at top of available memory */
> + /* Global Data is at top of available memory */
> dest_addr = gd->ram_size;
> + dest_addr -= GENERATED_GBL_DATA_SIZE;
> + dest_addr &= ~15;
> + gd->new_gd_addr = dest_addr;
> +
> + /* GDT is below Global Data */
> + dest_addr -= GDT_SIZE;
> + dest_addr &= ~15;
> + gd->gdt_addr = dest_addr;
> +
> + /* Stack is below GDT */
> gd->start_addr_sp = dest_addr;
>
> /* U-Boot is below the stack */
> @@ -279,6 +281,31 @@ void board_init_f_r(void)
> ;
> }
>
> +static int copy_gd_to_ram(void)
> +{
> + gd_t *ram_gd;
> +
> + /*
> + * Global data is still in temporary memory (the CPU cache).
> + * calculate_relocation_address() has set gd->new_gd_addr to
> + * where the global data lives in RAM but getting it there
> + * safely is a bit tricky due to the 'F-Segment Hack' that
> + * we need to use for x86
> + */
> + ram_gd = (gd_t *)gd->new_gd_addr;
> + memcpy((void *)ram_gd, gd, sizeof(gd_t));
> +
> + /*
> + * Reload the Global Descriptor Table so FS points to the
> + * in-RAM copy of Global Data (calculate_relocation_address()
> + * has already calculated the in-RAM location of the GDT)
> + */
> + ram_gd->gd_addr = (ulong)ram_gd;
> + init_gd(ram_gd, (u64 *)gd->gdt_addr);
> +
> + return 0;
> +}
> +
> void board_init_r(gd_t *id, ulong dest_addr)
> {
> #if defined(CONFIG_CMD_NET)
> @@ -288,15 +315,10 @@ void board_init_r(gd_t *id, ulong dest_addr)
> ulong size;
> #endif
> static bd_t bd_data;
> - static gd_t gd_data;
> init_fnc_t **init_fnc_ptr;
>
> show_boot_progress(0x21);
>
> - /* Global data pointer is now writable */
> - gd = &gd_data;
> - memcpy(gd, id, sizeof(gd_t));
> -
> /* compiler optimization barrier needed for GCC >= 3.4 */
> __asm__ __volatile__("" : : : "memory");
>
> --
> 1.7.5.2.317.g391b14
>
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Regards,
Simon
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