On Sun, Aug 21, 2011 at 10:07 PM, Al Viro <v...@zeniv.linux.org.uk> wrote: > On Sun, Aug 21, 2011 at 10:01:40PM -0400, Andrew Lutomirski wrote: > >> 3. We're worried that pt_regs-using compat syscalls might want the >> regs to appear to match the actual arguments (why?) > > run strace and you'll see why. >
I'm talking about the implementations of stub32_rt_sigreturn, sys32_rt_sigreturn, stub32_sigreturn, stub32_sigaltstack, stub32_execve, stub32_fork, stub32_clone, stub32_vfork, and stub32_iopl. I don't know what this has to do with strace or user ABI at all. >> 4. ptrace expects the "registers" when SYSCALL happens to match the >> int 0x80 convention. (This is, IMO, sick.) > > That's what ptrace is *for*. It's there to let debuggers play with > the program being debugged, including taking a look at the syscall > arguments and modifying them. In a predictable way, please. > It may be necessary, but I still think it's sick. Especially in the case of inlined SYSCALL, where the registers reported to ptrace do not match any register values that ever actually existed in CPU registers. Too late to fix it, though. Which still leaves the question of how to fix it. Restarting via an int 0x80-based helper might be the only option that leaves everything fully functional. --Andy ------------------------------------------------------------------------------ uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
