[POWERPC] zImage: Cleanup and improve zImage entry point
This patch re-organises the way the zImage wrapper code is entered, to
allow more flexibility on platforms with unusual entry conditions.
After this patch, a platform .o file has two options:
1) It can define a _zimage_start, in which case the platform code gets
control from the very beginning of execution. In this case the
platform code is responsible for relocating the zImage if necessary,
clearing the BSS, performing any platform specific initialization, and
finally calling start() to load and enter the kernel.
2) It can define platform_init(). In this case the generic crt0.S
handles initial entry, and calls platform_init() before calling
start(). The signature of platform_init() is changed, however, to
take up to 5 parameters (in r3..r7) as they come from the platform's
initial loader, instead of a fixed set of parameters based on OF's
usage.
When using the generic crt0.S, the platform .o can optionally
supply a custom stack to use, using the BSS_STACK() macro. If this
is not supplied, the crt0.S will assume that the loader has
supplied a usable stack.
In either case, the platform code communicates information to the
generic code (specifically, a PROM pointer for OF systems, and/or an
initrd image address supplied by the bootloader) via a global
structure "loader_info".
In addition the wrapper script is rearranged to ensure that the
platform .o is always linked first. This means that platforms where
the zImage entry point is at a fixed address or offset, rather than
being encoded in the binary header can be supported using option (1).
Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
index 3628d86..b1fc029 100644
--- a/arch/powerpc/boot/Makefile
+++ b/arch/powerpc/boot/Makefile
@@ -40,11 +40,11 @@
$(addprefix $(obj)/,$(zlib) main.o): $(addprefix $(obj)/,$(zliblinuxheader)) \
$(addprefix $(obj)/,$(zlibheader))
-src-wlib := string.S stdio.c main.c flatdevtree.c flatdevtree_misc.c \
+src-wlib := string.S crt0.S stdio.c main.c flatdevtree.c flatdevtree_misc.c \
ns16550.c serial.c simple_alloc.c div64.S util.S \
gunzip_util.c $(zlib)
src-plat := of.c
-src-boot := crt0.S $(src-wlib) $(src-plat) empty.c
+src-boot := $(src-wlib) $(src-plat) empty.c
src-boot := $(addprefix $(obj)/, $(src-boot))
obj-boot := $(addsuffix .o, $(basename $(src-boot)))
@@ -97,7 +97,7 @@
hostprogs-y := addnote addRamDisk hack-coff mktree
-extra-y := $(obj)/crt0.o $(obj)/wrapper.a $(obj-plat) $(obj)/empty.o \
+extra-y := $(obj)/wrapper.a $(obj-plat) $(obj)/empty.o \
$(obj)/zImage.lds $(obj)/zImage.coff.lds
wrapper :=$(srctree)/$(src)/wrapper
diff --git a/arch/powerpc/boot/crt0.S b/arch/powerpc/boot/crt0.S
index 70e65b1..3dc8d8f 100644
--- a/arch/powerpc/boot/crt0.S
+++ b/arch/powerpc/boot/crt0.S
@@ -16,6 +16,7 @@
_zimage_start_opd:
.long _zimage_start, 0, 0, 0
+ .weak _zimage_start
.globl _zimage_start
_zimage_start:
/* Work out the offset between the address we were linked at
@@ -44,7 +45,7 @@
addi r9,r9,4
bdnz 2b
- /* Do a cache flush for our text, in case OF didn't */
+ /* Do a cache flush for our text, in case the loader didn't */
3: lis r9,_start@ha
addi r9,r9,_start@l
add r9,r0,r9
@@ -59,6 +60,31 @@
sync
isync
- mr r6,r1
- b start
+ /* Clear the BSS */
+ lis r9,__bss_start@ha
+ addi r9,r9,__bss_start@l
+ lis r8,_end@ha
+ addi r8,r8,_end@l
+ li r0,0
+5: stw r0,0(r9)
+ addi r9,r9,4
+ cmplw cr0,r9,r8
+ blt 5b
+ /* Possibly set up a custom stack */
+.weak _platform_stack_top
+ lis r8,_platform_stack_top@ha
+ addi r8,r8,_platform_stack_top@l
+ cmpwi r8,0
+ beq 6f
+ lwz r1,0(r8)
+ li r0,0
+ stwu r0,-16(r1) /* establish a stack frame */
+6:
+
+ /* Call platform_init() */
+ bl platform_init
+
+ /* Call start */
+ mr r3,r1
+ b start
diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
index 05de6cf..8a60e13 100644
--- a/arch/powerpc/boot/main.c
+++ b/arch/powerpc/boot/main.c
@@ -254,21 +254,15 @@
struct platform_ops platform_ops;
struct dt_ops dt_ops;
struct console_ops console_ops;
+struct loader_info loader_info;
-void start(unsigned long a1, unsigned long a2, void *promptr, void *sp)
+void start(void *sp)
{
struct addr_range vmlinux, initrd;
kernel_entry_t kentry;
char cmdline[COMMAND_LINE_SIZE];
unsigned long ft_addr = 0;
- memset(__bss_start, 0, _end - __bss_start);
- memset(&platform_ops, 0, sizeof(platform_ops));
- memset(&dt_ops, 0, sizeof(dt_ops));
- memset(&console_ops, 0, sizeof(console_ops));
-
- if (platform_init(promptr, _dtb_start, _dtb_end))
- exit();
if (console_ops.open && (console_ops.open() < 0))
exit();
if (platform_ops.fixups)
@@ -278,7 +272,8 @@
_start, sp);
vmlinux = prep_kernel();
- initrd = prep_initrd(vmlinux, a1, a2);
+ initrd = prep_initrd(vmlinux, loader_info.initrd_addr,
+ loader_info.initrd_size);
/* If cmdline came from zimage wrapper or if we can edit the one
* in the dt, print it out and edit it, if possible.
@@ -298,7 +293,7 @@
if (ft_addr)
printf(" flat tree at 0x%lx\n\r", ft_addr);
else
- printf(" using OF tree (promptr=%p)\n\r", promptr);
+ printf(" using OF tree (promptr=%p)\n\r", loader_info.promptr);
if (console_ops.close)
console_ops.close();
@@ -307,7 +302,8 @@
if (ft_addr)
kentry(ft_addr, 0, NULL);
else
- kentry((unsigned long)initrd.addr, initrd.size, promptr);
+ kentry((unsigned long)initrd.addr, initrd.size,
+ loader_info.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 044f347..c6f0d97 100644
--- a/arch/powerpc/boot/of.c
+++ b/arch/powerpc/boot/of.c
@@ -267,7 +267,7 @@
call_prom("write", 3, 1, of_stdout_handle, buf, len);
}
-int platform_init(void *promptr, char *dt_blob_start, char *dt_blob_end)
+void platform_init(unsigned long a1, unsigned long a2, void *promptr)
{
platform_ops.image_hdr = of_image_hdr;
platform_ops.malloc = of_try_claim;
@@ -282,5 +282,7 @@
console_ops.write = of_console_write;
prom = (int (*)(void *))promptr;
- return 0;
+ loader_info.promptr = promptr;
+ loader_info.initrd_addr = a1;
+ loader_info.initrd_size = a2;
}
diff --git a/arch/powerpc/boot/ops.h b/arch/powerpc/boot/ops.h
index fa62ff2..cad4eee 100644
--- a/arch/powerpc/boot/ops.h
+++ b/arch/powerpc/boot/ops.h
@@ -59,7 +59,13 @@
void (*close)(void);
};
-int platform_init(void *promptr, char *dt_blob_start, char *dt_blob_end);
+struct loader_info {
+ void *promptr;
+ unsigned long initrd_addr, initrd_size;
+};
+extern struct loader_info loader_info;
+
+void start(void *sp);
int ft_init(void *dt_blob, unsigned int max_size, unsigned int max_find_device);
int serial_console_init(void);
int ns16550_console_init(void *devp, struct serial_console_data *scdp);
@@ -100,4 +106,8 @@
for(;;);
}
+#define BSS_STACK(size) \
+ static char _bss_stack[size]; \
+ void *_platform_stack_top = _bss_stack + sizeof(_bss_stack);
+
#endif /* _PPC_BOOT_OPS_H_ */
diff --git a/arch/powerpc/boot/wrapper b/arch/powerpc/boot/wrapper
index 024e4d4..157d8c8 100755
--- a/arch/powerpc/boot/wrapper
+++ b/arch/powerpc/boot/wrapper
@@ -191,7 +191,7 @@
if [ "$platform" != "miboot" ]; then
${CROSS}ld -m elf32ppc -T $lds -o "$ofile" \
- $object/crt0.o $platformo $tmp $object/wrapper.a
+ $platformo $tmp $object/wrapper.a
rm $tmp
fi
@@ -201,7 +201,9 @@
$object/addnote "$ofile"
;;
pmaccoff)
- ${CROSS}objcopy -O aixcoff-rs6000 --set-start 0x500000 "$ofile"
+ entry=`objdump -f "$ofile" | grep '^start address ' | \
+ cut -d' ' -f3`
+ ${CROSS}objcopy -O aixcoff-rs6000 --set-start "$entry" "$ofile"
$object/hack-coff "$ofile"
;;
esac
diff --git a/arch/powerpc/boot/zImage.coff.lds.S b/arch/powerpc/boot/zImage.coff.lds.S
index a360905..fe87a90 100644
--- a/arch/powerpc/boot/zImage.coff.lds.S
+++ b/arch/powerpc/boot/zImage.coff.lds.S
@@ -1,5 +1,6 @@
OUTPUT_ARCH(powerpc:common)
-ENTRY(_start)
+ENTRY(_zimage_start_opd)
+EXTERN(_zimage_start_opd)
SECTIONS
{
. = (5*1024*1024);
diff --git a/arch/powerpc/boot/zImage.lds.S b/arch/powerpc/boot/zImage.lds.S
index 4be3c64..f6e380f 100644
--- a/arch/powerpc/boot/zImage.lds.S
+++ b/arch/powerpc/boot/zImage.lds.S
@@ -1,5 +1,6 @@
OUTPUT_ARCH(powerpc:common)
ENTRY(_zimage_start)
+EXTERN(_zimage_start)
SECTIONS
{
. = (4*1024*1024);