Commit bf0cd83c authored by Paul Mackerras's avatar Paul Mackerras Committed by Juerg Haefliger

powerpc: Fix COFF zImage booting on old powermacs

BugLink: https://bugs.launchpad.net/bugs/1811647

[ Upstream commit 5564597d ]

Commit 6975a783 ("powerpc/boot: Allow building the zImage wrapper
as a relocatable ET_DYN", 2011-04-12) changed the procedure descriptor
at the start of crt0.S to have a hard-coded start address of 0x500000
rather than a reference to _zimage_start, presumably because having
a reference to a symbol introduced a relocation which is awkward to
handle in a position-independent executable.  Unfortunately, what is
at 0x500000 in the COFF image is not the first instruction, but the
procedure descriptor itself, that is, a word containing 0x500000,
which is not a valid instruction.  Hence, booting a COFF zImage
results in a "DEFAULT CATCH!, code=FFF00700" message from Open
Firmware.

This fixes the problem by (a) putting the procedure descriptor in the
data section and (b) adding a branch to _zimage_start as the first
instruction in the program.

Fixes: 6975a783 ("powerpc/boot: Allow building the zImage wrapper as a relocatable ET_DYN")
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarJuerg Haefliger <juergh@canonical.com>
Signed-off-by: default avatarStefan Bader <stefan.bader@canonical.com>
parent a50db137
...@@ -15,7 +15,7 @@ ...@@ -15,7 +15,7 @@
RELA = 7 RELA = 7
RELACOUNT = 0x6ffffff9 RELACOUNT = 0x6ffffff9
.text .data
/* A procedure descriptor used when booting this as a COFF file. /* A procedure descriptor used when booting this as a COFF file.
* When making COFF, this comes first in the link and we're * When making COFF, this comes first in the link and we're
* linked at 0x500000. * linked at 0x500000.
...@@ -23,6 +23,8 @@ RELACOUNT = 0x6ffffff9 ...@@ -23,6 +23,8 @@ RELACOUNT = 0x6ffffff9
.globl _zimage_start_opd .globl _zimage_start_opd
_zimage_start_opd: _zimage_start_opd:
.long 0x500000, 0, 0, 0 .long 0x500000, 0, 0, 0
.text
b _zimage_start
#ifdef __powerpc64__ #ifdef __powerpc64__
.balign 8 .balign 8
......
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