* [PATCH AUTOSEL 4.9 02/35] powerpc: Fix COFF zImage booting on old powermacs
[not found] <20181226224142.150866-1-sashal@kernel.org>
@ 2018-12-26 22:41 ` Sasha Levin
0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2018-12-26 22:41 UTC (permalink / raw)
To: stable, linux-kernel; +Cc: linuxppc-dev, Sasha Levin
From: Paul Mackerras <paulus@ozlabs•org>
[ Upstream commit 5564597d51c8ff5b88d95c76255e18b13b760879 ]
Commit 6975a783d7b4 ("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: 6975a783d7b4 ("powerpc/boot: Allow building the zImage wrapper as a relocatable ET_DYN")
Signed-off-by: Paul Mackerras <paulus@ozlabs•org>
Signed-off-by: Michael Ellerman <mpe@ellerman•id.au>
Signed-off-by: Sasha Levin <sashal@kernel•org>
---
arch/powerpc/boot/crt0.S | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/boot/crt0.S b/arch/powerpc/boot/crt0.S
index 5c2199857aa8..a3550e8f1a77 100644
--- a/arch/powerpc/boot/crt0.S
+++ b/arch/powerpc/boot/crt0.S
@@ -15,7 +15,7 @@
RELA = 7
RELACOUNT = 0x6ffffff9
- .text
+ .data
/* A procedure descriptor used when booting this as a COFF file.
* When making COFF, this comes first in the link and we're
* linked at 0x500000.
@@ -23,6 +23,8 @@ RELACOUNT = 0x6ffffff9
.globl _zimage_start_opd
_zimage_start_opd:
.long 0x500000, 0, 0, 0
+ .text
+ b _zimage_start
#ifdef __powerpc64__
.balign 8
--
2.19.1
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