[people/ms/u-boot.git] / examples / stubs.c

#include <exports.h>

#if defined(CONFIG_I386)
/*
 * x86 does not have a dedicated register to store the pointer to
 * the global_data. Thus the jump table address is stored in a
 * global variable, but such approach does not allow for execution
 * from flash memory. The global_data address is passed as argv[-1]
 * to the application program.
 */
static void **jt;
gd_t *global_data;

#define EXPORT_FUNC(x) \
	asm volatile (			\
"	.globl " #x "\n"		\
#x ":\n"				\
"	movl	%0, %%eax\n"		\
"	movl	jt, %%ecx\n"		\
"	jmp	*(%%ecx, %%eax)\n"	\
	: : "i"(XF_ ## x * sizeof(void *)) : "eax", "ecx");
#elif defined(CONFIG_PPC)
/*
 * r29 holds the pointer to the global_data, r11 is a call-clobbered
 * register
 */
#define EXPORT_FUNC(x) \
	asm volatile (			\
"	.globl " #x "\n"		\
#x ":\n"				\
"	lwz	%%r11, %0(%%r29)\n"	\
"	lwz	%%r11, %1(%%r11)\n"	\
"	mtctr	%%r11\n"		\
"	bctr\n"				\
	: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r11");
#elif defined(CONFIG_ARM)
/*
 * r8 holds the pointer to the global_data, ip is a call-clobbered
 * register
 */
#define EXPORT_FUNC(x) \
	asm volatile (			\
"	.globl " #x "\n"		\
#x ":\n"				\
"	ldr	ip, [r8, %0]\n"		\
"	ldr	pc, [ip, %1]\n"		\
	: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "ip");
#elif defined(CONFIG_MIPS)
/*
 * k0 ($26) holds the pointer to the global_data; t9 ($25) is a call-
 * clobbered register that is also used to set gp ($26). Note that the
 * jr instruction also executes the instruction immediately following
 * it; however, GCC/mips generates an additional `nop' after each asm
 * statement
 */
#define EXPORT_FUNC(x) \
	asm volatile (			\
"	.globl " #x "\n"		\
#x ":\n"				\
"	lw	$25, %0($26)\n"		\
"	lw	$25, %1($25)\n"		\
"	jr	$25\n"			\
	: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "t9");
#else
#error stubs definition missing for this architecture
#endif

/* This function is necessary to prevent the compiler from
 * generating prologue/epilogue, preparing stack frame etc.
 * The stub functions are special, they do not use the stack
 * frame passed to them, but pass it intact to the actual
 * implementation. On the other hand, asm() statements with
 * arguments can be used only inside the functions (gcc limitation)
 */
static void __attribute__((unused)) dummy(void)
{
#include <_exports.h>
}

void app_startup(char **argv)
{
#if defined(CONFIG_I386)
	/* x86 does not have a dedicated register for passing global_data */
	global_data = (gd_t *)argv[-1];
	jt = global_data->jt;
#endif
}

#undef EXPORT_FUNC
Commit	Line	Data
27b207fd WD	1	#include <exports.h>
	2
	3	#if defined(CONFIG_I386)
	4	/*
	5	* x86 does not have a dedicated register to store the pointer to
	6	* the global_data. Thus the jump table address is stored in a
	7	* global variable, but such approach does not allow for execution
	8	* from flash memory. The global_data address is passed as argv[-1]
	9	* to the application program.
	10	*/
	11	static void **jt;
77846748	12	gd_t *global_data;
27b207fd WD	13
	14	#define EXPORT_FUNC(x) \
	15	asm volatile ( \
	16	" .globl " #x "\n" \
	17	#x ":\n" \
	18	" movl %0, %%eax\n" \
	19	" movl jt, %%ecx\n" \
	20	" jmp *(%%ecx, %%eax)\n" \
	21	: : "i"(XF_ ## x * sizeof(void *)) : "eax", "ecx");
	22	#elif defined(CONFIG_PPC)
	23	/*
	24	* r29 holds the pointer to the global_data, r11 is a call-clobbered
	25	* register
	26	*/
	27	#define EXPORT_FUNC(x) \
	28	asm volatile ( \
	29	" .globl " #x "\n" \
	30	#x ":\n" \
	31	" lwz %%r11, %0(%%r29)\n" \
	32	" lwz %%r11, %1(%%r11)\n" \
	33	" mtctr %%r11\n" \
	34	" bctr\n" \
	35	: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "r11");
	36	#elif defined(CONFIG_ARM)
	37	/*
	38	* r8 holds the pointer to the global_data, ip is a call-clobbered
	39	* register
	40	*/
	41	#define EXPORT_FUNC(x) \
	42	asm volatile ( \
	43	" .globl " #x "\n" \
	44	#x ":\n" \
	45	" ldr ip, [r8, %0]\n" \
	46	" ldr pc, [ip, %1]\n" \
	47	: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "ip");
	48	#elif defined(CONFIG_MIPS)
	49	/*
	50	* k0 ($26) holds the pointer to the global_data; t9 ($25) is a call-
	51	* clobbered register that is also used to set gp ($26). Note that the
	52	* jr instruction also executes the instruction immediately following
	53	* it; however, GCC/mips generates an additional `nop' after each asm
	54	* statement
	55	*/
	56	#define EXPORT_FUNC(x) \
	57	asm volatile ( \
	58	" .globl " #x "\n" \
	59	#x ":\n" \
	60	" lw $25, %0($26)\n" \
	61	" lw $25, %1($25)\n" \
	62	" jr $25\n" \
	63	: : "i"(offsetof(gd_t, jt)), "i"(XF_ ## x * sizeof(void *)) : "t9");
	64	#else
	65	#error stubs definition missing for this architecture
	66	#endif
	67
	68	/* This function is necessary to prevent the compiler from
	69	* generating prologue/epilogue, preparing stack frame etc.
	70	* The stub functions are special, they do not use the stack
	71	* frame passed to them, but pass it intact to the actual
	72	* implementation. On the other hand, asm() statements with
	73	* arguments can be used only inside the functions (gcc limitation)
	74	*/
	75	static void __attribute__((unused)) dummy(void)
	76	{
77	#include <_exports.h>
78	}
79
80	void app_startup(char **argv)
81	{
82	#if defined(CONFIG_I386)
83	/* x86 does not have a dedicated register for passing global_data */
77846748 WD	84	global_data = (gd_t *)argv[-1];
77846748 WD	85	jt = global_data->jt;
27b207fd WD	86	#endif
	87	}
	88
	89	#undef EXPORT_FUNC