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ia32 System call emulation in x86_64
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Somu Peri
Nov 10, 2009, 11:52:22 AM11/10/09
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I would really appreciate it if anyone can shed light into how are
system calls for 32 bit binaries handled in a 64 bit kernel (or
atleast give me pointers other than the source code itself). More
precisely I would like to know how and where the kernel decides to use
the 32 bit syscall table rather than 64 bit syscall table.
Thanks
S
system calls for 32 bit binaries handled in a 64 bit kernel (or
atleast give me pointers other than the source code itself). More
precisely I would like to know how and where the kernel decides to use
the 32 bit syscall table rather than 64 bit syscall table.
Thanks
S
David Schwartz
Nov 10, 2009, 12:09:14 PM11/10/09
to
The kernel doesn't decide. The process can call into either the 32-bit
syscall table or the 64-bit syscall table. Believe it or not, 64-bit
processes can call into the 32-bit syscall table if they want to.
(This can create security vulnerabilities if tracing/filtering tools
assume a 64-bit process must be making 64-bit syscalls!)
32-bit processes, of course, typically only know how to make 32-bit
syscalls. 64-bit processes, assuming they're built by typical
development tools, will call into libraries that make 64-bit syscalls.
(But nothing stops them from making a 32-bit syscall if they want to.)
DS
Somu Peri
Nov 10, 2009, 4:45:07 PM11/10/09
to
How does the process decide which table to call into? More importantly
how does it tell the kernel which table to use?
Thanks
S
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