Add support for parsing Linux ATAGs such as you'd see from uboot or

redboot.  Support is very preiminary and likely needs some work. Also,
do some minor code shuffling of the FreeBSD /boot/loader metadata
parsing code.  This code is preliminary and should be used with
caution.

sys/arm/arm/machdep.c

@@ -80,6 +80,7 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm_pager.h>
 
 #include <machine/armreg.h>
+#include <machine/atags.h>
 #include <machine/cpu.h>
 #include <machine/machdep.h>
 #include <machine/md_var.h>
@@ -110,6 +111,20 @@ extern int *end;
 extern vm_offset_t ksym_start, ksym_end;
 #endif
 
+#if defined(LINUX_BOOT_ABI)
+#define LBABI_MAX_BANKS	10
+
+uint32_t board_id;
+struct arm_lbabi_tag *atag_list;
+uint32_t revision;
+uint64_t serial;
+char linux_command_line[LBABI_MAX_COMMAND_LINE + 1];
+char atags[LBABI_MAX_COMMAND_LINE * 2];
+uint32_t memstart[LBABI_MAX_BANKS];
+uint32_t memsize[LBABI_MAX_BANKS];
+uint32_t membanks;
+#endif
+
 void
 sendsig(catcher, ksi, mask)
 	sig_t catcher;
@@ -712,11 +727,73 @@ fake_preload_metadata(struct arm_boot_params *abp __unused)
 	return (lastaddr);
 }
 
+#if defined(LINUX_BOOT_ABI)
 vm_offset_t
-default_parse_boot_param(struct arm_boot_params *abp)
+linux_parse_boot_param(struct arm_boot_params *abp)
 {
-	vm_offset_t lastaddr;
+	struct arm_lbabi_tag *walker;
+
+	/*
+	 * Linux boot ABI: r0 = 0, r1 is the board type (!= 0) and r2
+	 * is atags or dtb pointer.  If all of these aren't satisfied,
+	 * then punt.
+	 */
+	if (!(abp->abp_r0 == 0 && abp->abp_r1 != 0 && abp->abp_r2 != 0))
+		return 0;
+
+	board_id = abp->abp_r1;
+	walker = (struct arm_lbabi_tag *)
+	    (abp->abp_r2 + KERNVIRTADDR - KERNPHYSADDR);
+
+	/* xxx - Need to also look for binary device tree */
+	if (ATAG_TAG(walker) != ATAG_CORE)
+		return 0;
+
+	atag_list = walker;
+	while (ATAG_TAG(walker) != ATAG_NONE) {
+		switch (ATAG_TAG(walker)) {
+		case ATAG_CORE:
+			break;
+		case ATAG_MEM:
+			if (membanks < LBABI_MAX_BANKS) {
+				memstart[membanks] = walker->u.tag_mem.start;
+				memsize[membanks] = walker->u.tag_mem.size;
+			}
+			membanks++;
+			break;
+		case ATAG_INITRD2:
+			break;
+		case ATAG_SERIAL:
+			serial = walker->u.tag_sn.low |
+			    ((uint64_t)walker->u.tag_sn.high << 32);
+			break;
+		case ATAG_REVISION:
+			revision = walker->u.tag_rev.rev;
+			break;
+		case ATAG_CMDLINE:
+			/* XXX open question: Parse this for boothowto? */
+			bcopy(walker->u.tag_cmd.command, linux_command_line,
+			      ATAG_SIZE(walker));
+			break;
+		default:
+			break;
+		}
+		walker = ATAG_NEXT(walker);
+	}
+
+	/* Save a copy for later */
+	bcopy(atag_list, atags,
+	    (char *)walker - (char *)atag_list + ATAG_SIZE(walker));
+
+	return fake_preload_metadata(abp);
+}
+#endif
+
 #if defined(FREEBSD_BOOT_LOADER)
+vm_offset_t
+freebsd_parse_boot_param(struct arm_boot_params *abp)
+{
+	vm_offset_t lastaddr = 0;
 	void *mdp;
 	void *kmdp;
 
@@ -724,32 +801,45 @@ default_parse_boot_param(struct arm_boot_params *abp)
 	 * Mask metadata pointer: it is supposed to be on page boundary. If
 	 * the first argument (mdp) doesn't point to a valid address the
 	 * bootloader must have passed us something else than the metadata
-	 * ptr... In this case we want to fall back to some built-in settings.
+	 * ptr, so we give up.  Also give up if we cannot find metadta section
+	 * the loader creates that we get all this data out of.
 	 */
-	mdp = (void *)(abp->abp_r0 & ~PAGE_MASK);
 
-	kmdp = NULL;
-	/* Parse metadata and fetch parameters (move to common machdep.c?) */
-	if (mdp != NULL) {
-		preload_metadata = mdp;
-		kmdp = preload_search_by_type("elf kernel");
-		if (kmdp != NULL) {
-			boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-			kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
-			lastaddr = MD_FETCH(kmdp, MODINFOMD_KERNEND,
-			    vm_offset_t);
+	if ((mdp = (void *)(abp->abp_r0 & ~PAGE_MASK)) == NULL)
+		return 0;
+	preload_metadata = mdp;
+	kmdp = preload_search_by_type("elf kernel");
+	if (kmdp == NULL)
+		return 0;
+
+	boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
+	kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+	lastaddr = MD_FETCH(kmdp, MODINFOMD_KERNEND, vm_offset_t);
 #ifdef DDB
-			ksym_start = MD_FETCH(kmdp, MODINFOMD_SSYM, uintptr_t);
-			ksym_end = MD_FETCH(kmdp, MODINFOMD_ESYM, uintptr_t);
+	ksym_start = MD_FETCH(kmdp, MODINFOMD_SSYM, uintptr_t);
+	ksym_end = MD_FETCH(kmdp, MODINFOMD_ESYM, uintptr_t);
+#endif
+	preload_addr_relocate = KERNVIRTADDR - KERNPHYSADDR;
+	return lastaddr;
+}
 #endif
-		} else
-			lastaddr = fake_preload_metadata(abp);
 
-		preload_addr_relocate = KERNVIRTADDR - KERNPHYSADDR;
-	} else
+vm_offset_t
+default_parse_boot_param(struct arm_boot_params *abp)
+{
+	vm_offset_t lastaddr;
+
+#if defined(LINUX_BOOT_ABI)
+	if ((lastaddr = linux_parse_boot_param(abp)) != 0)
+		return lastaddr;
 #endif
-		/* Fall back to hardcoded metadata. */
-		lastaddr = fake_preload_metadata(abp);
+#if defined(FREEBSD_BOOT_LOADER)
+	if ((lastaddr = freebsd_parse_boot_param(abp)) != 0)
+		return lastaddr;
+#endif
+	/* Fall back to hardcoded metadata. */
+	lastaddr = fake_preload_metadata(abp);
+
 	return lastaddr;
 }
 

sys/arm/include/machdep.h

@@ -13,6 +13,8 @@ void prefetch_abort_handler(trapframe_t *);
 void undefinedinstruction_bounce(trapframe_t *);
 struct arm_boot_params;
 vm_offset_t default_parse_boot_param(struct arm_boot_params *abp);
+vm_offset_t freebsd_parse_boot_param(struct arm_boot_params *abp);
+vm_offset_t linux_parse_boot_param(struct arm_boot_params *abp);
 vm_offset_t fake_preload_metadata(struct arm_boot_params *abp);
 vm_offset_t parse_boot_param(struct arm_boot_params *abp);
 

sys/conf/options.arm

@@ -20,6 +20,7 @@ FREEBSD_BOOT_LOADER	opt_global.h
 IXP4XX_FLASH_SIZE	opt_global.h
 KERNPHYSADDR		opt_global.h
 KERNVIRTADDR		opt_global.h
+LINUX_BOOT_ABI		opt_global.h
 LOADERRAMADDR		opt_global.h
 PHYSADDR		opt_global.h
 QEMU_WORKAROUNDS	opt_global.h