Re: [patch] gdbarch_syscall_pc_increment

[Aleksandar Ristovski <aristovski at qnx dot com>]

On 12-12-12 10:30 AM, Yao Qi wrote:
> Hi,
> I don't understand why do you add a gdbarch hook, but use it only in a
> target-specific part?  The goal of gdbarch hooks is about hiding the
> difference of ports and giving a common interface to the common part of
> GDB.  If your issue is arm specific, we don't need this new gdbarch hook
> at all.


This is generic for a given OS that happens to increment instruction 
pointer to allow user code to e.g. set errno.

I provided only arm implementation, but other target cpus would need the 
same if they implement software single stepping.

Increment is cpu specific for a given architecture.


> If I understand your problem correctly, you have to define your own
> function 'arm_neutrino_syscall_next_pc' in your file
> arm-neutrino-tdep.c, and install it on function pointer
> 'syscall_next_pc' (in 'struct gdbarch_tdep' in arm-tdep.h) in
> 'arm_neutrino_init_abi'.  Please have a look on how 'syscall_next_pc' is
> set in arm-linux-tdep.c.  Then you can compute the pc for your own os in
> 'arm_neutrino_syscall_next_pc'.  Hope it helps.


No, the destination is not a single address as we do not know the 
outcome of the syscall. It may come back with the instruction pointer of 
the next instruction after 'svc' but also 4 bytes later (4 bytes in our 
case, some other kernel may implement it differently).


Hope this clarifies,

Aleksandar