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.
This gcc bug does not exist in SLES9 gcc33 toolchain, but it is present in
gcc4.0+, likely also in gcc3.4. Compiling a testcase without any -O produces
also correct code.
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)
...
simple testcase:
int f(unsigned);
void g(void)
{
unsigned a;
unsigned int b = (unsigned long)(void*)(&a);
f(b);
}
asm should look like this:
c: 38 61 00 70 addi r3,r1,112
10: 78 63 00 20 clrldi r3,r3,32
14: 48 00 00 01 bl 14 <.g+0x14>
But instead it looks like:
c: 38 61 00 70 addi r3,r1,112
10: 54 63 00 36 rlwinm r3,r3,0,0,27
14: 48 00 00 01 bl 14 <.g+0x14>
So just uninline prom_getprop to workaround this gcc bug.
c000000000409034 <.prom_getprop>:
c000000000409054: 7c bc 2b 78 mr r28,r5
c000000000409074: 7b 88 00 20 clrldi r8,r28,32
...
c00000000040b29c <.prom_init>:
c00000000040b47c: e8 82 a1 d8 ld r4,-24104(r2)
c00000000040b480: 80 61 00 74 lwz r3,116(r1)
c00000000040b484: 7f 85 e3 78 mr r5,r28
c00000000040b488: 38 c0 00 10 li r6,16
c00000000040b48c: 4b c1 c2 95 bl c000000000027720
<.prom_getprop>
...
c00000000040b4b4: 80 61 00 74 lwz r3,116(r1)
Signed-off-by: Olaf Hering <[EMAIL PROTECTED]>
arch/powerpc/kernel/prom_init.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
Index: linux-2.6.16-rc5-olh/arch/powerpc/kernel/prom_init.c
===================================================================
--- linux-2.6.16-rc5-olh.orig/arch/powerpc/kernel/prom_init.c
+++ linux-2.6.16-rc5-olh/arch/powerpc/kernel/prom_init.c
@@ -421,8 +421,8 @@ static int __init prom_next_node(phandle
return 1;
}
}
-
-static int inline prom_getprop(phandle node, const char *pname,
+/* do not mark as inline to work around gcc bug */
+static int __init prom_getprop(phandle node, const char *pname,
void *value, size_t valuelen)
{
return call_prom("getprop", 4, 1, node, ADDR(pname),
--
Summary: pointer truncation in arch/powerpc/kernel/prom_init.c
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: olh at suse dot de
GCC build triplet: powerpc64-linux
GCC host triplet: powerpc64-linux
GCC target triplet: powerpc64-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26549
