This patch adds code, linker script and makefile support to allow
building the zImage wrapper around the kernel as a position independent
executable. This results in an ET_DYN instead of an ET_EXEC ELF output
file, which can be loaded at any location by the firmware and will
process its own relocations to work correctly at the loaded address.
This is of interest particularly since the standard ePAPR image format
must be an ET_DYN (although this patch alone is not sufficient to
produce a fully ePAPR compliant boot image).
Note for now we don't enable building with -pie for anything.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Currently we set the start of the .text section to be 4Mb for pSeries.
In situations where the zImage is > 8Mb we'll fail to boot (due to
overlapping with OF). Move .text in a zImage from 4MB to 64MB
(well past OF).
We still will not be able to load large zImage unless we also move OF,
to that end, add a note to the zImage ELF to move OF to 32Mb. If this
is the very first kernel booted then we'll need to move OF manually by
setting real-base.
Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
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>
The "wrapper" script was using the wrong names for the initrd and
dtb (device-tree blob) sections. This fixes it, and also ensures
the symbols for the start and end of the dtb get defined correctly.
Signed-off-by: Paul Mackerras <paulus@samba.org>
This puts the knowledge of how to create various sorts of zImage
wrappers into a script called "wrapper" that could be used outside of
the kernel tree. This changes arch/powerpc/boot so it first builds
the files that the wrapper script needs, then runs it to create
whatever flavours of zImage are required.
This version does uImages as well. The zImage names are changed
slightly; zImage.pseries is the one with the PT_NOTE program header
entry added, and zImage.pmac is the one without. If the
zImage.pseries gets made, it will also get hardlinked to zImage;
otherwise, if zImage.pmac is made, it gets hardlinked to zImage.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Michael Ellerman
Tony Breeds
David Gibson
Paul Mackerras