syscall to userland interface

[Oliver Pinter]

On 5/11/13, Alfred Perlstein <bright at mu.org> wrote:
> On 5/11/13 1:23 AM, Karl Dreger wrote:
>>
>> I am feeling rather stupid at the moment, but I can't find the assembler
>>
>> files that you are referring to. Do you mean that every syscall under
>>
>> sys/kern/*.c has a corresponding .S file in src/lib/libc/?
>
> Nope, the .S files are under the object directory:
>
>> When you build the system a whole bunch of assembler files are
>> automatically generated that define the functions you are looking for.
>>
>> Look for .S files under the object directory.
>>
>> Those assembler files have the magic to cause a system call to happen.
>>
>> example: src/lib/libc/getauid.S  (note, this file is GENERATED, it's not
>> part of src.)
>
>
>
>>
>>
>> The actual transition from user to kernelland and back probably takes
>>
>> place via the assembler routines in sys/i386/i386. Most notably
>> exception.s
>>
>> for my i386 cpu.
>>
>>
>> What my question boils down to is this: when running fork and friends
>>
>> from userland they are invoked as:
>>
>> fork();, open();, read();, close(); ...
>>
>>
>> but are defined as:
>>
>> sys_fork(), sys_open(), sys_read(), sys_close(), ...
>>
>> in their actual c definition.
>>
>> If the assembler files that you spoke about answer this discrepancy,
>>
>> then the reason why the penny hasn't dropped yet is because I haven't
>> found them.
>>
>>
> Again, they are generated as part of build.  You will NOT find them
> during a checkout.

 cd /usr/obj/*/lib/libc/
ls *.S

>
> -Alfred
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