Re: kernel panic on readBytes

10 Apr 2008

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Hey Timur,
Where does the physical address in inStruct->offset come from?
getPhysicalSegment()?
The address is passed in from userspace.  I wrote a little daemon that
simply goes from 0x0 to the highest possible address (I figure that
out by getting the maximum amount of ram on the machine through a
sysctl call) and pass it to the kernel extension. The kernel then
returns a 32-bit hash value for each page. I thought that should work
ok, but is it a problem?

Timur
...
Dan

...
...
...
The problem is that kMemoryTypePhysical != kIOMemoryTypePhysical64. The
former is a 32-bit I/O physical address.  The later is a 64-bit CPU
physical
...
...
address.
Right, makes sense. I tried doing what you described and ended up with:
Unresolved kernel trap(cpu 1): 0x300 - Data access
DAR=0x6572436D00001000 PC=0x00000000000B3E40
Latest crash info for cpu 1:
 Exception state (sv=0x26c76500)
    PC=0x000B3E40; MSR=0x00009030; DAR=0x00001000; DSISR=0x00200000;
LR=0x000B26A8; R1=0x268F2A20; XCP=0x0000000C (0x300 - Data access)
    Backtrace:
0x000B2618 0x003622DC 0x26C95310 0x26C949AC 0x0037AA38 0x00377CB8
       0x00093E0C 0x0002C1B4 0x00024C88 0x000B2C4C 0x00000000
       backtrace terminated - frame not mapped or invalid: 0xBFFFE260
I hate to be the guy who posts code and asks for help, but I'm pretty
stuck at this point, as the documentation I could find on this was
scarce at best. Anyway, here is what I tried running:
IOOptionBits opt = kIOMemoryTypePhysical64 | kIODirectionOut;
struct IOPhysicalRange* range =
(IOPhysicalRange*)IOMalloc(sizeof(struct IOPhysicalRange));
range->address = inStruct->offset;
range->length = MEM_READ_CHUNK;
task_t task;
IOLog("calling withoptions\n");
IOSleep(2000);
IOMemoryDescriptor* d = IOMemoryDescriptor::withOptions(range, 1, 0, task,
opt);
IOLog("withoptions ran\n");
IOSleep(5000);
IOFree(range, sizeof(IOPhysicalRange));
if (d == NULL)
{
 IOLog("IO-Init failed on the page %u\n", inStruct->offset);
 goto End;
}
ret = d->prepare();
if (ret != kIOReturnSuccess)
{
 IOLog("IO-Prepare failed on the page %u\n", inStruct->offset);
 goto End;
}
char* buf = (char*) IOMalloc(MEM_READ_CHUNK);
int copied;
IOLog("printing: %d %d %d\n", (int)buf, MEM_READ_CHUNK, inStruct->offset);
copied = d->readBytes(0, buf, MEM_READ_CHUNK);
It prints out "calling with options" in the system log but not
"withoptions ran". Did I screw up that call as well?
Thank you,
Timur

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Timur Alperovich

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