Messages in this thread | | | Date | Fri, 26 Jan 2018 18:07:22 +0000 | From | Al Viro <> | Subject | Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast path with retpolines on |
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On Fri, Jan 26, 2018 at 09:40:23AM -0800, Linus Torvalds wrote: > On Fri, Jan 26, 2018 at 7:57 AM, Andy Lutomirski <luto@kernel.org> wrote: > > > > I gave the rearrangement like this a try yesterday and it's a bit of a > > mess. Part of the problem is that there are a bunch of pieces of code > > that expect sys_xyz() to be actual callable functions. > > That's not supposed to be a mess. > > That's part of why we do that whole indirection through SYSC##xyz to > sys##_xyz: the asm-callable ones will do the full casting of > troublesome arguments (some architectures have C calling sequence > rules that have security issues, so we need to make sure that the > arguments actually follow the right rules and 'int' arguments are > properly sign-extended etc). > > So that whole indirection could be made to *also* create another > version of the syscall that instead took the arguments from ptregs. > > We already do exactly that for the tracing events: look how > FTRACE_SYSCALLS ends up creating that extra metadata. > > The ptreg version should be done the same way: don't make 'sys_xyz()' > take a struct ptregs, instead make those SYSCALL_DEFINE*() macros > create a _new_ function called 'ptregs_xyz()' and then that function > does the argument unpacking. > > Then the x86 system call table can just be switched over to call those > ptreg versions instead.
Umm... What about other architectures? Or do you want SYSCALL_DEFINE... to be per-arch? I wonder how much would that "go through pt_regs" hurt on something like sparc...
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