On Fri, Mar 30, 2018 at 12:16:02PM +0200, Ingo Molnar wrote: > > * Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> wrote: > > > A few questions remain, from important stuff to bikeshedding: > > > > 1) Is it acceptable to pass the existing struct pt_regs to the sys_*() > > kernel functions in emulate_vsyscall(), or should it use a hand-crafted > > struct pt_regs instead? > > I think so: we already have task_pt_regs() which gives access to the real return > registers on the kernel stack. > > I think as long as we constify the pointer, we should pass in the real thing. Good idea. I have updated the patchset accordingly. > > 2) Is it the right approach to generate the __sys32_ia32_*() names to > > include in the syscall table on-the-fly, or should they all be listed > > in arch/x86/entry/syscalls/syscall_32.tbl ? > > I think as a general principle all system call tables should point to the > first-hop wrapper symbol name (i.e. __sys32_ia32_*() in this case), not to the > generic symbol name - even though we could generate the former from the latter. > > The more indirection in these tables, the harder to read they become I think. > > > 3) I have chosen to name the default 64-bit syscall stub sys_*(), same as > > the "normal" syscall, and the IA32_EMULATION compat syscall stub > > compat_sys_*(), same as the "normal" compat syscall. Though this > > might cause some confusion, as the "same" function uses a different > > calling convention and different parameters on x86, it has the > > advantages that > > - the kernel *has* a function sys_*() implementing the syscall, > > so those curious in stack traces etc. will find it in plain > > sight, > > - it is easier to handle in the syscall table generation, and > > - error injection works the same. > > I don't think there should be a symbol space overlap, that will only lead to > confusion. The symbols can be _similar_, with a prefix, underscores or so, but > they shouldn't match I think. OK, I'll wait for a few more opinions on these two related issues, and update the code accordingly then. > > The whole series is available at > > > > https://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux.git syscalls-WIP > > BTW., I'd like all these bits to go through the x86 tree. > > What is the expected merge route of the generic preparatory bits? My current plan is to push the 109 patch bomb to remove in-kernel calls to syscalls directly to Linus once v4.16 is released. For this series of seven patches, I am content with them going upstream through the x86 tree (once that contains a backmerge of Linus' tree or the syscalls tree, obviously). IMO, these seven patches should be kept together, and not routed upstream through different channels. Thanks, Dominik
