Date: Fri, 20 Jan 2012 22:38:45 +0100 From: Anders Gavare <gavare@gmail.com> To: freebsd-ppc@freebsd.org Subject: possible bug? OF_getprop() < sizeof() Message-ID: <1327095525.2825.10.camel@localhost.localdomain>
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If I understood things correctly, there's a possible minor bug in
ofw_machdep.c for PowerPC, in parse_ofw_memory:
/*
* Get #address-cells from root node, defaulting to 1 if it cannot
* be found.
*/
phandle = OF_finddevice("/");
if (OF_getprop(phandle, "#address-cells", &address_cells,
sizeof(address_cells)) < sizeof(address_cells))
address_cells = 1;
if (OF_getprop(phandle, "#size-cells", &size_cells,
sizeof(size_cells)) < sizeof(size_cells))
size_cells = 1;
Running the code in GXemul, it seems that the comparison between
OF_getprop's return value (-1 in case the property is not found) and the
sizeof value is done as unsigned integers.
...
<ofwcall(0x908600,&smp_no_rendevous_barrier,&ofw_rendezvous_dispatch,&smp_no_rendevous_barrier,..)>
<0xfff00000(0x908600,"D",0,0,..)>
[ of: getprop(1, "#address-cells", 0x908e7c, 4) ]
[ of: WARNING: getprop: no property '#address-cells' at handle 1 (device
'') ]
<smp_no_rendevous_barrier(0x9085e4,"D",0,0,..)>
<spinlock_exit(0x9085e4,"D",0,0,..)>
<critical_exit(0x9085e4,"D",0,0,..)>
<ofw_real_stop(-1,"D",0,0,..)>
0068bcf8: 2b830003 cmplwi cr7,r3,3
BREAKPOINT: pc = 0x68bcf8
(The instruction has not yet executed.)
GXemul> print r3
0xffffffffffffffff
GXemul> s 10
0068bcf8: 2b830003 cmplwi cr7,r3,3
0068bcfc: 419d000c bc 12,29,0x68bd08 <parse_ofw_memory+0x5c>
0068bd08: 7fc3f378 mr r3,r30
0068bd0c: 3c800090 lis r4,144
0068bd10: 3884deb8 subi r4,r4,8520
0068bd14: 38a10818 addi r5,r1,2072
0068bd18: 38c00004 li r6,4
0068bd1c: 4bfe0361 bl 0x66c07c <OF_getprop>
<OF_getprop(0x1,"#size-cells",0x908e78,4,..)>
Real machines perhaps always have #address-cells and #size-cells
properties for the / node, so this problem perhaps does not show up IRL.
However, if this pattern OF_getprop(...) < sizeof(..) is common, maybe
there are other similar bugs.
Or did I misunderstand the semantics of cmplwi?
(The binary and source code were from
ftp://ftp.freebsd.org/pub/FreeBSD/releases/powerpc/powerpc/9.0-RELEASE.)
Anders
(not subscribed to the list)
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