Hi Michael,
On 26/06/2024 03:56, Michael Schmitz wrote:
Jean-Michel,
On 24/06/24 20:56, Jean-Michel Hautbois wrote:
When I printk the do_page_fault first debug, I get for the first call
to ls:
bash-5.2# ls
[ 14.700000] do page fault:
[ 14.700000] regs->sr=0x0, regs->pc=0x70069ee6, address=0x70069ee6,
0, (ptrval)
Page not present, read fault. Please disable obfuscation of kernel
pointer addresses by printk. Maybe also disable address space
randomization while debugging this.
Randomization is disabled, I think I don't have hash pointers... Will
heck again, thanks for the explanation.
This call works almost fine (I still have the assert failed:
folio->private != NULL issue).
And when I call it a second time, I get:
bash-5.2# ls
[ 19.820000] do page fault:
[ 19.820000] regs->sr=0x0, regs->pc=0x6011d65a, address=0x700e2004,
2, (ptrval)
Page not present, write fault.
It would be helpful if you could get a dump of /proc/1/maps before the
execve() syscall in your helloworld init replacement. That might confirm
all these addresses are legit (assuming mappings survive across
execve(), that is), and what they correspond to.
Executing mount /proc will make it impossible to then call cat
/proc/1/maps :-(. Can I enable a printk somewhere in the kernel to do
the same maybe ?
JM
The address corresponds to the defined zone ELF_ET_DYN_BASE as I set
it to 0x70000000.
regs->pc is not the same as the address. It might be unrelevant, but
any help is appreciated to understand the process behind :-).
I keep digging, and I am in the asm part which fears me a bit !
I don't see that you'd need to look at any asm code here.
Cheers,
Michael
Thanks !
JM
