dded _main (like crt0)

util/baremetal/lib/_main.c

@@ -0,0 +1,73 @@
+#include <boot/linuxbios_tables.h>
+#include <preboot.h>
+
+#define DPRINTF( x... )
+
+struct lb_memory *lbmem;
+
+unsigned long find_ramtop( struct lb_memory *mem)
+{
+	int high_entry=0;
+	unsigned long int high_start=0;
+	int mem_entries;
+	int i;
+
+
+	mem_entries = (mem->size - sizeof(*mem))/sizeof(mem->map[0]);
+
+	for(i=0; i<mem_entries; i++) {
+		if(mem->map[i].type == LB_MEM_RAM) 
+			if(mem->map[i].start > high_start) {
+				high_entry=i;
+				high_start = mem->map[i].start;
+			}
+	}
+
+	return(high_start + mem->map[high_entry].size);
+
+}
+
+unsigned long int preboot_ramtop;
+pre_boot_param_t *preboot_param;
+
+
+int _main(pre_boot_param_t *pbp) {
+
+	if(strcmp(pbp->sig, "$PBP$")) {
+		lbmem = get_lbmem();
+
+		DPRINTF("Got lbmem struct: %08x\n", (unsigned int) lbmem);
+
+		preboot_ramtop = find_ramtop(lbmem);
+		DPRINTF("Top of RAM = %08x\n", preboot_ramtop);
+		preboot_param = (pre_boot_param_t *) preboot_ramtop - sizeof(pre_boot_param_t);
+		if( strcmp(preboot_param->sig, "$PBP$")) {
+			preboot_ramtop -= 4096;
+			strcpy(preboot_param->sig, "$PBP$");
+			preboot_param->lbmem = lbmem;
+			preboot_param->stack = preboot_ramtop;
+
+			__asm__ __volatile__(
+				"movl %%ebp, %%eax\n"
+				"subl %%esp, %%eax\n"
+				"movl %0, %%esp\n" 
+				"movl %0, %%ebp\n"
+				"pushl %%ebp\n" 
+				"subl %%eax, %%esp\n" :: "d" (preboot_ramtop));
+
+			// reserve a stack
+			preboot_param->free_ramtop = preboot_ramtop - 0x8000;
+			preboot_param->stacksize = 0x8000;
+
+			DPRINTF("ramtop = %08x, free_ramtop = %08x\n", preboot_ramtop, preboot_param->free_ramtop);
+		}
+
+		DPRINTF("Calling main\n");
+
+		return(main());
+	} else {
+		DPRINTF("Pre boot environment already set up, calling main\n");
+		preboot_param = pbp;
+		return(main());
+	}
+}