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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoPlainText>Hi All,<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>I'm sorry if this has come up before somewhere on the list, but:<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Is it possible to tag those opcodes in the llvm bitcode that a) require supervisor (Ring 0) priviledge, or b) cause a trap, e.g. INT or SYSCALL on x86?<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>My reasoning for asking is that the new MCJIT is able to JIT embedded asm (containing such opcodes) but for implementing a sandboxed runtime environment it would be nice to be able to intercept such instructions and force a call to a JIT-host callback allowing the host to emulate kernel calls in the JIT executeable.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>This would allow a JIT-based user-level 'virtual machine' runtime to be implemented without requiring special code layout and rules (as in Google's Native Client), just a set of standard libraries providing wrappers to OS-level syscalls all compiled as llvm bitcode.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Am I right in thinking that the opcode information for each architecture is all defined by the TableGen tables, and a modification to that and the underlying MCInstr infrastructure is all that is required?<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>This is all very blue-sky thinking at the moment, but I may be able to do some of the development required once I have the opinions of those who know the guts of llvm better than I.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Many thanks<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Rick Taylor<o:p></o:p></p><p class=MsoPlainText>Tropical Storm Software Ltd. <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>