Ah, excellent observation: makes complete sense, I hadn't noticed that that wasn't a numeric constant.
On Tue, Sep 15, 2015, at 19:13, Matthew Fernandez wrote: > Hi Corey, > > I didn't write this code, so someone else may wish to correct me with a more > accurate answer, but my understanding was > that this was related to how the sysenter and sysexit instructions work. The > sysexit instruction restores your > instruction pointer from edx, not directly from eip. This means edx has to > contain the userspace address we want to > return to when executing sysexit in the kernel. Instead of having the kernel > do this, the userspace stub takes care of > it instead. You'll notice just prior to the label, it is used to load the > address of the sysenter instruction into edx. > This way, provided the kernel preserves the user's edx, the syscall returns > to the correct location in userspace. > > Matt > > On 16/09/15 08:58, Corey Richardson wrote: > > For example, here: > > https://github.com/seL4/seL4/blob/master/libsel4/arch_include/x86/sel4/arch/syscalls.h#L26 > > > > What use is the label? Does it align the instruction or do other > > ABI-important things? > > > > ________________________________ > > The information in this e-mail may be confidential and subject to legal > professional privilege and/or copyright. National ICT Australia Limited > accepts no liability for any damage caused by this email or its attachments. -- /cmr _______________________________________________ Devel mailing list [email protected] https://sel4.systems/lists/listinfo/devel
