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| author | Olaf Hering <olh@suse.de> | 2006-03-23 21:50:59 +0100 |
|---|---|---|
| committer | Paul Mackerras <paulus@samba.org> | 2006-03-27 14:48:32 +1100 |
| commit | 6088857b169c64e6e9672a2a66e76db3e957d5db (patch) | |
| tree | 9864cf2887f365456d6edac28a78cd939b48dc52 | |
| parent | ca3e91cb0cd53da70621f85d24a080b23751a013 (diff) | |
| download | linux-6088857b169c64e6e9672a2a66e76db3e957d5db.tar.gz linux-6088857b169c64e6e9672a2a66e76db3e957d5db.tar.bz2 linux-6088857b169c64e6e9672a2a66e76db3e957d5db.zip | |
[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>
| -rw-r--r-- | arch/powerpc/kernel/head_64.S | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S index 35084f3a841b..7e7f7d243304 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 */ |