Re: Calling syscalls from x86-64 kernel results in a crash on Opteronmachines

[Constantine Gavrilov]

Brian Gerst wrote:

> You should never use the unistd.h macros from kernel space.  Call 
> sys_foo() directly.  This may mean you have to export it.  The reason 
> it crashes is that the "syscall" opcode used by the x86-64 macros 
> (unlike the "int $0x80" for i386) causes a fault when already running 
> in kernel space.
>
> --
>                 Brian Gerst

I can see from the crash report that the fault happens. I want to 
understand why.

I can use workarounds. (Calling sys_foo() directly from module can be a 
problem -- I would have to know the "versioned"  function name or the 
address of the function within the kernel space.  Calling an entry from 
the syscall table is much easier.)

--
----------------------------------------
Constantine Gavrilov
Kernel Developer
Qlusters Software Ltd
1 Azrieli Center, Tel-Aviv
Phone: +972-3-6081977
Fax:   +972-3-6081841
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