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authorOlaf Hering <olh@suse.de>2006-03-23 21:50:59 +0100
committerPaul Mackerras <paulus@samba.org>2006-03-27 14:48:32 +1100
commit6088857b169c64e6e9672a2a66e76db3e957d5db (patch)
tree9864cf2887f365456d6edac28a78cd939b48dc52 /arch/powerpc
parentca3e91cb0cd53da70621f85d24a080b23751a013 (diff)
[PATCH] correct the comment about stackpointer alignment in __boot_from_prom
The address of variable val in prom_init_stdout is passed to prom_getprop. prom_getprop casts the pointer to u32 and passes it to call_prom in the hope that OpenFirmware stores something there. But the pointer is truncated in the lower bits and the expected value is stored somewhere else. In my testing I had a stackpointer of 0x0023e6b4. val was at offset 120, wich has address 0x0023e72c. But the value passed to OF was 0x0023e728. c00000000040b710: 3b 01 00 78 addi r24,r1,120 ... c00000000040b754: 57 08 00 38 rlwinm r8,r24,0,0,28 ... c00000000040b784: 80 01 00 78 lwz r0,120(r1) ... c00000000040b798: 90 1b 00 0c stw r0,12(r27) ... The stackpointer came from 32bit code. The chain was yaboot -> zImage -> vmlinux PowerMac OpenFirmware does appearently not handle the ELF sections correctly. If yaboot was compiled in /usr/src/packages/BUILD/lilo-10.1.1/yaboot, then the stackpointer is unaligned. But the stackpointer is correct if yaboot is compiled in /tmp/yaboot. This bug triggered since 2.6.15, now prom_getprop is an inline function. gcc clears the lower bits, instead of just clearing the upper 32 bits. Signed-off-by: Olaf Hering <olh@suse.de> Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/kernel/head_64.S6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 35084f3a841..7e7f7d24330 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -1544,7 +1544,11 @@ _STATIC(__boot_from_prom)
mr r28,r6
mr r27,r7
- /* Align the stack to 16-byte boundary for broken yaboot */
+ /*
+ * Align the stack to 16-byte boundary
+ * Depending on the size and layout of the ELF sections in the initial
+ * boot binary, the stack pointer will be unalignet on PowerMac
+ */
rldicr r1,r1,0,59
/* Make sure we are running in 64 bits mode */