[POWERPC] zImage: Cleanup and improve prep_kernel()

This patch rewrites prep_kernel() in the zImage wrapper code to be
clearer and more flexible.  Notable changes:

	- Handling of the initrd image from prep_kernel() has moved
into a new prep_initrd() function.
	- The address of the initrd image is now added as device tree
properties, as the kernel expects.
	- We only copy a packaged initrd image to a new location if it
is in danger of being clobbered when the kernel moves to its final
location, instead of always.
	- By default we decompress the kernel directly to address 0,
instead of requiring it to relocate itself.  Platforms (such as OF)
where doing this could clobber still-live firmware data structures can
override the vmlinux_alloc hook to provide an alternate place to
decompress the kernel.
	- We no longer pass lots of information between functions in
global variables.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 114 insertions, 66 deletions

diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
index 404620a9e73..05de6cfafee 100644
--- a/arch/powerpc/boot/main.c
+++ b/arch/powerpc/boot/main.c
@@ -33,24 +33,21 @@ extern char _dtb_end[];
 static struct gunzip_state gzstate;
 
 struct addr_range {
-        unsigned long addr;
+        void *addr;
         unsigned long size;
-        unsigned long memsize;
 };
-static struct addr_range vmlinux;
-static struct addr_range vmlinuz;
-static struct addr_range initrd;
-
-static unsigned long elfoffset;
-static int is_64bit;
 
-static char elfheader[256];
+struct elf_info {
+        unsigned long loadsize;
+        unsigned long memsize;
+        unsigned long elfoffset;
+};
 
 typedef void (*kernel_entry_t)(unsigned long, unsigned long, void *);
 
 #undef DEBUG
 
-static int is_elf64(void *hdr)
+static int parse_elf64(void *hdr, struct elf_info *info)
 {
         Elf64_Ehdr *elf64 = hdr;
         Elf64_Phdr *elf64ph;
@@ -74,15 +71,14 @@ static int is_elf64(void *hdr)
         if (i >= (unsigned int)elf64->e_phnum)
                 return 0;
 
-        elfoffset = (unsigned long)elf64ph->p_offset;
-        vmlinux.size = (unsigned long)elf64ph->p_filesz;
-        vmlinux.memsize = (unsigned long)elf64ph->p_memsz;
+        info->loadsize = (unsigned long)elf64ph->p_filesz;
+        info->memsize = (unsigned long)elf64ph->p_memsz;
+        info->elfoffset = (unsigned long)elf64ph->p_offset;
 
-        is_64bit = 1;
         return 1;
 }
 
-static int is_elf32(void *hdr)
+static int parse_elf32(void *hdr, struct elf_info *info)
 {
         Elf32_Ehdr *elf32 = hdr;
         Elf32_Phdr *elf32ph;
@@ -98,7 +94,6 @@ static int is_elf32(void *hdr)
               elf32->e_machine         == EM_PPC))
                 return 0;
 
-        elf32 = (Elf32_Ehdr *)elfheader;
         elf32ph = (Elf32_Phdr *) ((unsigned long)elf32 + elf32->e_phoff);
         for (i = 0; i < elf32->e_phnum; i++, elf32ph++)
                 if (elf32ph->p_type == PT_LOAD)
@@ -106,24 +101,26 @@ static int is_elf32(void *hdr)
         if (i >= elf32->e_phnum)
                 return 0;
 
-        elfoffset = elf32ph->p_offset;
-        vmlinux.size = elf32ph->p_filesz;
-        vmlinux.memsize = elf32ph->p_memsz;
+        info->loadsize = elf32ph->p_filesz;
+        info->memsize = elf32ph->p_memsz;
+        info->elfoffset = elf32ph->p_offset;
         return 1;
 }
 
-static void prep_kernel(unsigned long a1, unsigned long a2)
+static struct addr_range prep_kernel(void)
 {
+        char elfheader[256];
+        void *vmlinuz_addr = _vmlinux_start;
+        unsigned long vmlinuz_size = _vmlinux_end - _vmlinux_start;
+        void *addr = 0;
+        struct elf_info ei;
         int len;
 
-        vmlinuz.addr = (unsigned long)_vmlinux_start;
-        vmlinuz.size = (unsigned long)(_vmlinux_end - _vmlinux_start);
-
         /* gunzip the ELF header of the kernel */
-        gunzip_start(&gzstate, (void *)vmlinuz.addr, vmlinuz.size);
+        gunzip_start(&gzstate, vmlinuz_addr, vmlinuz_size);
         gunzip_exactly(&gzstate, elfheader, sizeof(elfheader));
 
-        if (!is_elf64(elfheader) && !is_elf32(elfheader)) {
+        if (!parse_elf64(elfheader, &ei) && !parse_elf32(elfheader, &ei)) {
                 printf("Error: not a valid PPC32 or PPC64 ELF file!\n\r");
                 exit();
         }
@@ -135,55 +132,92 @@ static void prep_kernel(unsigned long a1, unsigned long a2)
          * the kernel bss must be claimed (it will be zero'd by the
          * kernel itself)
          */
-        printf("Allocating 0x%lx bytes for kernel ...\n\r", vmlinux.memsize);
-        vmlinux.addr = (unsigned long)malloc(vmlinux.memsize);
-        if (vmlinux.addr == 0) {
-                printf("Can't allocate memory for kernel image !\n\r");
-                exit();
+        printf("Allocating 0x%lx bytes for kernel ...\n\r", ei.memsize);
+
+        if (platform_ops.vmlinux_alloc) {
+                addr = platform_ops.vmlinux_alloc(ei.memsize);
+        } else {
+                if ((unsigned long)_start < ei.memsize) {
+                        printf("Insufficient memory for kernel at address 0!"
+                               " (_start=%lx)\n\r", _start);
+                        exit();
+                }
         }
 
+        /* Finally, gunzip the kernel */
+        printf("gunzipping (0x%p <- 0x%p:0x%p)...", addr,
+               vmlinuz_addr, vmlinuz_addr+vmlinuz_size);
+        /* discard up to the actual load data */
+        gunzip_discard(&gzstate, ei.elfoffset - sizeof(elfheader));
+        len = gunzip_finish(&gzstate, addr, ei.memsize);
+        printf("done 0x%lx bytes\n\r", len);
+
+        flush_cache(addr, ei.loadsize);
+
+        return (struct addr_range){addr, ei.memsize};
+}
+
+static struct addr_range prep_initrd(struct addr_range vmlinux,
+                                     unsigned long initrd_addr,
+                                     unsigned long initrd_size)
+{
+        void *devp;
+        u32 initrd_start, initrd_end;
+
+        /* If we have an image attached to us, it overrides anything
+         * supplied by the loader. */
+        if (_initrd_end > _initrd_start) {
+                printf("Attached initrd image at 0x%p-0x%p\n\r",
+                       _initrd_start, _initrd_end);
+                initrd_addr = (unsigned long)_initrd_start;
+                initrd_size = _initrd_end - _initrd_start;
+        } else if (initrd_size > 0) {
+                printf("Using loader supplied ramdisk at 0x%lx-0x%lx\n\r",
+                       initrd_addr, initrd_addr + initrd_size);
+        }
+
+        /* If there's no initrd at all, we're done */
+        if (! initrd_size)
+                return (struct addr_range){0, 0};
+
         /*
-         * Now find the initrd
-         *
-         * First see if we have an image attached to us.  If so
-         * allocate memory for it and copy it there.
+         * If the initrd is too low it will be clobbered when the
+         * kernel relocates to its final location.  In this case,
+         * allocate a safer place and move it.
          */
-        initrd.size = (unsigned long)(_initrd_end - _initrd_start);
-        initrd.memsize = initrd.size;
-        if (initrd.size > 0) {
+        if (initrd_addr < vmlinux.size) {
+                void *old_addr = (void *)initrd_addr;
+
                 printf("Allocating 0x%lx bytes for initrd ...\n\r",
-                       initrd.size);
-                initrd.addr = (unsigned long)malloc((u32)initrd.size);
-                if (initrd.addr == 0) {
+                       initrd_size);
+                initrd_addr = (unsigned long)malloc(initrd_size);
+                if (! initrd_addr) {
                         printf("Can't allocate memory for initial "
-                                        "ramdisk !\n\r");
+                               "ramdisk !\n\r");
                         exit();
                 }
-                printf("initial ramdisk moving 0x%lx <- 0x%lx "
-                        "(0x%lx bytes)\n\r", initrd.addr,
-                        (unsigned long)_initrd_start, initrd.size);
-                memmove((void *)initrd.addr, (void *)_initrd_start,
-                        initrd.size);
-                printf("initrd head: 0x%lx\n\r",
-                                *((unsigned long *)initrd.addr));
-        } else if (a2 != 0) {
-                /* Otherwise, see if yaboot or another loader gave us an initrd */
-                initrd.addr = a1;
-                initrd.memsize = initrd.size = a2;
-                printf("Using loader supplied initrd at 0x%lx (0x%lx bytes)\n\r",
-                       initrd.addr, initrd.size);
+                printf("Relocating initrd 0x%p <- 0x%p (0x%lx bytes)\n\r",
+                       initrd_addr, old_addr, initrd_size);
+                memmove((void *)initrd_addr, old_addr, initrd_size);
         }
 
-        /* Eventually gunzip the kernel */
-        printf("gunzipping (0x%lx <- 0x%lx:0x%0lx)...",
-               vmlinux.addr, vmlinuz.addr, vmlinuz.addr+vmlinuz.size);
-        /* discard up to the actual load data */
-        gunzip_discard(&gzstate, elfoffset - sizeof(elfheader));
-        len = gunzip_finish(&gzstate, (void *)vmlinux.addr,
-                            vmlinux.memsize);
-        printf("done 0x%lx bytes\n\r", len);
+        printf("initrd head: 0x%lx\n\r", *((unsigned long *)initrd_addr));
+
+        /* Tell the kernel initrd address via device tree */
+        devp = finddevice("/chosen");
+        if (! devp) {
+                printf("Device tree has no chosen node!\n\r");
+                exit();
+        }
+
+        initrd_start = (u32)initrd_addr;
+        initrd_end = (u32)initrd_addr + initrd_size;
+
+        setprop(devp, "linux,initrd-start", &initrd_start,
+                sizeof(initrd_start));
+        setprop(devp, "linux,initrd-end", &initrd_end, sizeof(initrd_end));
 
-        flush_cache((void *)vmlinux.addr, vmlinux.size);
+        return (struct addr_range){(void *)initrd_addr, initrd_size};
 }
 
 /* A buffer that may be edited by tools operating on a zImage binary so as to
@@ -223,6 +257,7 @@ struct console_ops console_ops;
 
 void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
 {
+        struct addr_range vmlinux, initrd;
         kernel_entry_t kentry;
         char cmdline[COMMAND_LINE_SIZE];
         unsigned long ft_addr = 0;
@@ -242,7 +277,8 @@ void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
         printf("\n\rzImage starting: loaded at 0x%p (sp: 0x%p)\n\r",
                _start, sp);
 
-        prep_kernel(a1, a2);
+        vmlinux = prep_kernel();
+        initrd = prep_initrd(vmlinux, a1, a2);
 
         /* If cmdline came from zimage wrapper or if we can edit the one
          * in the dt, print it out and edit it, if possible.
@@ -271,8 +307,7 @@ void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
         if (ft_addr)
                 kentry(ft_addr, 0, NULL);
         else
-                /* XXX initrd addr/size should be passed in properties */
-                kentry(initrd.addr, initrd.size, promptr);
+                kentry((unsigned long)initrd.addr, initrd.size, promptr);
 
         /* console closed so printf below may not work */
         printf("Error: Linux kernel returned to zImage boot wrapper!\n\r");
diff --git a/arch/powerpc/boot/of.c b/arch/powerpc/boot/of.c
index 0182f384f3e..044f34770b9 100644
--- a/arch/powerpc/boot/of.c
+++ b/arch/powerpc/boot/of.c
@@ -208,6 +208,17 @@ static void of_image_hdr(const void *hdr)
         }
 }
 
+static void *of_vmlinux_alloc(unsigned long size)
+{
+        void *p = malloc(size);
+
+        if (!p) {
+                printf("Can't allocate memory for kernel image!\n\r");
+                exit();
+        }
+        return p;
+}
+
 static void of_exit(void)
 {
         call_prom("exit", 0, 0);
@@ -261,6 +272,7 @@ int platform_init(void *promptr, char *dt_blob_start, char *dt_blob_end)
         platform_ops.image_hdr = of_image_hdr;
         platform_ops.malloc = of_try_claim;
         platform_ops.exit = of_exit;
+        platform_ops.vmlinux_alloc = of_vmlinux_alloc;
 
         dt_ops.finddevice = of_finddevice;
         dt_ops.getprop = of_getprop;
diff --git a/arch/powerpc/boot/ops.h b/arch/powerpc/boot/ops.h
index 8abb6516bb7..fa62ff223e7 100644
--- a/arch/powerpc/boot/ops.h
+++ b/arch/powerpc/boot/ops.h
@@ -25,6 +25,7 @@ struct platform_ops {
         void    (*free)(void *ptr);
         void *  (*realloc)(void *ptr, unsigned long size);
         void    (*exit)(void);
+        void *  (*vmlinux_alloc)(unsigned long size);
 };
 extern struct platform_ops platform_ops;