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x86: Place global data below stack before entering C

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By reserving space for the Global Data immediately below the stack during
assembly level initialisation, the C declaration of the static global data
can be removed, along with the 'RAM Bootstrap' function. This results in
cleaner code, and the ability to pass boot-up flags from assembler into C
This commit is contained in:
Graeme Russ 2010-10-07 20:03:29 +11:00
parent 5a3876d2ac
commit 161b3589ea
3 changed files with 37 additions and 37 deletions
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8
arch/i386/cpu/start.S
View File

@ -25,6 +25,7 @@
#include <config.h>
#include <version.h>
#include <asm/global_data.h>
.section .text
@ -127,6 +128,13 @@ mem_ok:
/* Set the upper memory limit parameter */
subl $CONFIG_SYS_STACK_SIZE, %eax
/* Reserve space for global data */
subl $(GD_SIZE * 4), %eax
/* %eax points to the global data structure */
movl %esp, (GD_RAM_SIZE * 4)(%eax)
movl %ebx, (GD_FLAGS * 4)(%eax)
call board_init_f /* Enter, U-boot! */
/* indicate (lack of) progress */

24
arch/i386/include/asm/global_data.h
View File

@ -33,6 +33,8 @@
* Keep it *SMALL* and remember to set CONFIG_SYS_GBL_DATA_SIZE > sizeof(gd_t)
*/
#ifndef __ASSEMBLY__
typedef struct {
bd_t *bd;
unsigned long flags;
@ -49,6 +51,26 @@ typedef struct {
char env_buf[32]; /* buffer for getenv() before reloc. */
} gd_t;
extern gd_t *gd;
#endif
/* Word Offsets into Global Data - MUST match struct gd_t */
#define GD_BD 0
#define GD_FLAGS 1
#define GD_BAUDRATE 2
#define GD_HAVE_CONSOLE 3
#define GD_RELOC_OFF 4
#define GD_ENV_ADDR 5
#define GD_ENV_VALID 6
#define GD_CPU_CLK 7
#define GD_BUS_CLK 8
#define GD_RAM_SIZE 9
#define GD_RESET_STATUS 10
#define GD_JT 11
#define GD_SIZE 12
/*
* Global Data Flags
*/
@ -61,8 +83,6 @@ typedef struct {
#define GD_FLG_DISABLE_CONSOLE 0x00040 /* Disable console (in & out) */
#define GD_FLG_ENV_READY 0x00080 /* Environment imported into hash table */
extern gd_t *gd;
#define DECLARE_GLOBAL_DATA_PTR
#endif /* __ASM_GBL_DATA_H */

42
arch/i386/lib/board.c
View File

@ -54,8 +54,6 @@ extern ulong _i386boot_rel_dyn_end;
extern ulong _i386boot_bss_start;
extern ulong _i386boot_bss_size;
void ram_bootstrap (void *, ulong);
const char version_string[] =
U_BOOT_VERSION" (" U_BOOT_DATE " - " U_BOOT_TIME ")";
@ -164,13 +162,12 @@ init_fnc_t *init_sequence[] = {
NULL,
};
static gd_t gd_data;
gd_t *gd;
/*
* Load U-Boot into RAM, initialize BSS, perform relocation adjustments
*/
void board_init_f (ulong stack_limit)
void board_init_f (ulong gdp)
{
void *text_start = &_i386boot_text_start;
void *u_boot_cmd_end = &__u_boot_cmd_end;
@ -184,12 +181,9 @@ void board_init_f (ulong stack_limit)
ulong rel_offset;
Elf32_Rel *re;
void (*start_func)(void *, ulong);
uboot_size = (ulong)u_boot_cmd_end - (ulong)text_start;
dest_addr = (void *)stack_limit - (uboot_size + (ulong)bss_size);
dest_addr = (void *)gdp - (uboot_size + (ulong)bss_size);
rel_offset = text_start - dest_addr;
start_func = ram_bootstrap - rel_offset;
/* First stage CPU initialization */
if (cpu_init_f() != 0)
@ -213,38 +207,16 @@ void board_init_f (ulong stack_limit)
*(ulong *)(re->r_offset - rel_offset) -= (Elf32_Addr)rel_offset;
}
((gd_t *)gdp)->reloc_off = rel_offset;
((gd_t *)gdp)->flags |= GD_FLG_RELOC;
/* Enter the relocated U-Boot! */
start_func(dest_addr, rel_offset);
(board_init_r - rel_offset)((gd_t *)gdp, (ulong)dest_addr);
/* NOTREACHED - board_init_f() does not return */
while(1);
}
/*
* We cannot initialize gd_data in board_init_f() because we would be
* attempting to write to flash (I have even tried using manual relocation
* adjustments on pointers but it just won't work) and board_init_r() does
* not have enough arguments to allow us to pass the relocation offset
* straight up. This bootstrap function (which runs in RAM) is used to
* setup gd_data in order to pass the relocation offset to the rest of
* U-Boot.
*
* TODO: The compiler optimization barrier is intended to stop GCC from
* optimizing this function into board_init_f(). It seems to work without
* it, but I've left it in to be sure. I think also that the barrier in
* board_init_r() is no longer needed, but left it in 'just in case'
*/
void ram_bootstrap (void *dest_addr, ulong rel_offset)
{
/* compiler optimization barrier needed for GCC >= 3.4 */
__asm__ __volatile__("": : :"memory");
/* tell others: relocation done */
gd_data.reloc_off = rel_offset;
gd_data.flags |= GD_FLG_RELOC;
board_init_r(&gd_data, (ulong)dest_addr);
}
void board_init_r(gd_t *id, ulong dest_addr)
{
char *s;