On Tue, 25 Jan 2005, Michael Halcrow wrote:
I am not entirely clear on the function that ``[ 222 ] = sys_ni_syscall,'' at the end of the table in syscalls.h is supposed to serve.
This says that syscall number 222 is not implemented, which it isn't on i386 (not defined).
Syscalls in UML contstitutes new territory for me.
Mostly the same as syscalls in any other architecture. A big table with function pointers to each syscall, indexed by the syscall number.
As each architecture has it's own syscall table but UML sharing the syscall numbers with the host architecture things get a little confusing sometimes. And in addition the UML syscall table often lags behind a little, missing the newer syscalls.
Note that the main syscall table is defined in arch/um/kernel/sys_call_table.c, the define in the include/asm/sysdep/syscalls.h is just the part of the syscall table which is specific to a certain host architecture.
To add a new generic syscall you should
1. Add it to asm-xxx/unistd.h of each architecture, except for um which picks it up from the host architecture.
2. Add it to the syscall table of earch architecture, um included.
To add a new i386 only syscall you should
1. Add it to asm-i386/unistd.h
2. Add it to the i386 syscall table
3. Add it to um i386 specific syscall table in asm-um/sysdep-i386/syscall.h
I would assume that the __NR_* assignments in the UML environment are identical to those of the host system.
They are. UML directly includes unistd.h from the host architecture.
That means that request_key, for example, maps to identifier 288 on the i386 architecture, right?
Which should have their appropriate _NR_xxx identifiers defined. For maintenance reasons the syscall table should be built using _NR_xxx identifiers, not the absolute numbers.
Regards Henrik
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