Messages in this thread | | | Date | Wed, 9 Jun 2010 11:14:31 -0700 | From | Sukadev Bhattiprolu <> | Subject | Re: [PATCH v21 011/100] eclone (11/11): Document sys_eclone |
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Albert Cahalan [acahalan@gmail.com] wrote: | On Tue, Jun 1, 2010 at 9:38 PM, Sukadev Bhattiprolu | <sukadev@linux.vnet.ibm.com> wrote: | > | Come on, seriously, you know it's ia64 and hppa that | > | have issues. Maybe the nommu ports also have issues. | > | | > | The only portable way to specify the stack is base and offset, | > | with flags or magic values for "share" and "kernel managed". | > | > Ah, ok, we have not yet ported to IA64 and I see now where the #ifdef | > comes in. | > | > But are you saying that we should force x86 and other architectures to | > specify base and offset for eclone() even though they currently specify | > just the stack pointer to clone() ? | | Even for x86, it's an easier API. Callers would be specifying | two numbers they already have: the argument and return value | for malloc. Currently the numbers must be added together, | destroying information, except on hppa (must not add size) | and ia64 (must use what I'm proposing already).
I agree its easier and would avoid #ifdefs in the applications.
Peter, Arnd, Roland - do you have any concerns with requiring all architectures to specify the stack to eclone() as [base, offset]
To recap, currently we have
struct clone_args { u64 clone_flags_high; /* * Architectures can use child_stack for either the stack pointer or * the base of of stack. If child_stack is used as the stack pointer, * child_stack_size must be 0. Otherwise child_stack_size must be * set to size of allocated stack. */ u64 child_stack; u64 child_stack_size; u64 parent_tid_ptr; u64 child_tid_ptr; u32 nr_pids; u32 reserved0; };
sys_eclone(u32 flags_low, struct clone_args * __user cargs, int cargs_size, pid_t * __user pids)
Most architecutres would specify the stack pointer in ->child_stack and ignore the ->child_stack_size.
IA64 specifies the *stack-base* in ->child_stack and the stack size in ->child_stack_size.
Albert and Randy point out that this would require #ifdefs in the application code that intends to be portable across say IA64 and x86.
Can we instead have all architectures specify [base, size] ?
Thanks
Sukadev
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