krf Syscall support: miscellaneous

We should support faulting these syscalls.

[x] vhangup
[x] sysctl
[x] prctl
[ ] arch_prctl
[x] adjtime
[x] adjtimex
[x] pivot_root
[ ] iopl
[ ] nfsservctl
[x] readahead

That list is not exhaustive; there are definitely others.

Each of the above probably belongs to one or more groups.

Jun 05 '19 04:06 woodruffw

How to decide to which groups each syscall belongs?

Oct 09 '19 20:10 layderv

How to decide to which groups each syscall belongs?

The manpages (man 2 <whatever>) should help with that. The major ones are fs (touches the filesystem), io (does any sort of I/O), net (does any sort of networking), proc (does any sort of process management), and time (deals with the system clock). Check out the other syscall specs for reference.

Oct 09 '19 20:10 woodruffw

I was going to add these as well:

< src/module/codegen/linux/arch_prctl.yml
proto: int option, unsigned long arg2
parms: option, arg2
errors:
  - EFAULT
  - EINVAL
  - EPERM
profiles:
  - fs
  - proc

< src/module/codegen/linux/iopl.yml
proto: int level
parms: level
errors:
  - ENOSYS
  - EINVAL
  - EPERM
profiles:
  - io
  - proc

With them, I cannot build:


In file included from /src/module/linux/syscalls.h:40:0,
                 from /src/module/linux/syscalls.c:1:
/src/module/linux/syscalls.gen.h:57:19: error: ‘sys_iopl’ undeclared here (not in a function); did you mean ‘sys_ipc’?
 asmlinkage typeof(sys_iopl) krf_sys_iopl;
                   ^~~~~~~~
                   sys_ipc
In file included from /src/module/linux/syscalls.h:40:0,
                 from /src/module/linux/krf.c:10:
/src/module/linux/syscalls.gen.h:57:19: error: ‘sys_iopl’ undeclared here (not in a function); did you mean ‘sys_ipc’?
 asmlinkage typeof(sys_iopl) krf_sys_iopl;
                   ^~~~~~~~
                   sys_ipc
/src/module/linux/syscalls.gen.h:178:19: error: ‘sys_arch_prctl’ undeclared here (not in a function); did you mean ‘__NR_arch_prctl’?
 asmlinkage typeof(sys_arch_prctl) krf_sys_arch_prctl;
                   ^~~~~~~~~~~~~~
                   __NR_arch_prctl
/src/module/linux/syscalls.gen.h:178:19: error: ‘sys_arch_prctl’ undeclared here (not in a function); did you mean ‘__NR_arch_prctl’?
 asmlinkage typeof(sys_arch_prctl) krf_sys_arch_prctl;
                   ^~~~~~~~~~~~~~
                   __NR_arch_prctl
scripts/Makefile.build:330: recipe for target '/src/module/linux/krf.o' failed
make[3]: *** [/src/module/linux/krf.o] Error 1
make[3]: *** Waiting for unfinished jobs....
In file included from /src/module/linux/syscalls.c:10:0:
/src/module/linux/syscalls.gen.x:473:17: error: ‘krf_sys_iopl’ redeclared as different kind of symbol
 long asmlinkage krf_sys_iopl(int level) {
                 ^~~~~~~~~~~~
In file included from /src/module/linux/syscalls.h:40:0,
                 from /src/module/linux/syscalls.c:1:
/src/module/linux/syscalls.gen.h:57:29: note: previous declaration of ‘krf_sys_iopl’ was here
 asmlinkage typeof(sys_iopl) krf_sys_iopl;
                             ^~~~~~~~~~~~
In file included from /src/module/linux/syscalls.c:10:0:
/src/module/linux/syscalls.gen.x: In function ‘krf_sys_iopl’:
/src/module/linux/syscalls.gen.x:477:12: error: called object ‘krf_sys_internal_iopl’ is not a function or function pointer
     return krf_sys_internal_iopl(level);
            ^~~~~~~~~~~~~~~~~~~~~
In file included from /src/module/linux/syscalls/internal.h:33:0,
                 from /src/module/linux/syscalls.c:2:
/src/module/linux/syscalls/internal.gen.h:57:18: note: declared here
 typeof(sys_iopl) krf_sys_internal_iopl;
                  ^~~~~~~~~~~~~~~~~~~~~
In file included from /src/module/linux/syscalls.c:10:0:
/src/module/linux/syscalls.gen.x:479:12: error: called object ‘real_iopl’ is not a function or function pointer
     return real_iopl(level);
            ^~~~~~~~~
/src/module/linux/syscalls.gen.x:474:21: note: declared here
   typeof(sys_iopl) *real_iopl = (void *)krf_sys_call_table[__NR_iopl];
                     ^~~~~~~~~
/src/module/linux/syscalls.gen.x: At top level:
/src/module/linux/syscalls.gen.x:1562:17: error: ‘krf_sys_arch_prctl’ redeclared as different kind of symbol
 long asmlinkage krf_sys_arch_prctl(int option, unsigned long arg2) {
                 ^~~~~~~~~~~~~~~~~~
In file included from /src/module/linux/syscalls.h:40:0,
                 from /src/module/linux/syscalls.c:1:
/src/module/linux/syscalls.gen.h:178:35: note: previous declaration of ‘krf_sys_arch_prctl’ was here
 asmlinkage typeof(sys_arch_prctl) krf_sys_arch_prctl;
                                   ^~~~~~~~~~~~~~~~~~
In file included from /src/module/linux/syscalls.c:10:0:
/src/module/linux/syscalls.gen.x: In function ‘krf_sys_arch_prctl’:
/src/module/linux/syscalls.gen.x:1566:12: error: called object ‘krf_sys_internal_arch_prctl’ is not a function or function pointer
     return krf_sys_internal_arch_prctl(option, arg2);
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /src/module/linux/syscalls/internal.h:33:0,
                 from /src/module/linux/syscalls.c:2:
/src/module/linux/syscalls/internal.gen.h:178:24: note: declared here
 typeof(sys_arch_prctl) krf_sys_internal_arch_prctl;
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /src/module/linux/syscalls.c:10:0:
/src/module/linux/syscalls.gen.x:1568:12: error: called object ‘real_arch_prctl’ is not a function or function pointer
     return real_arch_prctl(option, arg2);
            ^~~~~~~~~~~~~~~
/src/module/linux/syscalls.gen.x:1563:27: note: declared here
   typeof(sys_arch_prctl) *real_arch_prctl = (void *)krf_sys_call_table[__NR_arch_prctl];
                           ^~~~~~~~~~~~~~~
/src/module/linux/syscalls.gen.x: In function ‘krf_sys_iopl’:
/src/module/linux/syscalls.gen.x:481:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/src/module/linux/syscalls.gen.x: In function ‘krf_sys_arch_prctl’:
/src/module/linux/syscalls.gen.x:1570:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

Have you ever seen anything similar?

Oct 10 '19 21:10 layderv

Have you ever seen anything similar?

Not exactly, but some things that it could be:

We might be missing an #include for the appropriate kernel header for those symbols
You might be building on a version of the kernel that doesn't include those syscalls. In particular, iopl(2) is a 32-bit x86 thing and probably isn't implemented or exposed on 64-bit builds

Oct 10 '19 21:10 woodruffw

Have you ever seen anything similar?

Not exactly, but some things that it could be:

* We might be missing an `#include` for the appropriate kernel header for those symbols

* You might be building on a version of the kernel that doesn't include those syscalls. In particular, `iopl(2)` is a 32-bit x86 thing and probably isn't implemented or exposed on 64-bit builds

You're right. If you know of a way to build for x86, I'd go with it; otherwise I will go for a new VM and use that instead

Oct 14 '19 18:10 layderv

You're right. If you know of a way to build for x86, I'd go with it; otherwise I will go for a new VM and use that instead

Hmm, it's possible that KRF doesn't build at all with x86_32 -- it definitely makes assumptions about running on x86 in general, and I've only ever tested and used it on x86_64. I'd say it's okay to table x86_32-specific syscalls for now and focus on other ones; I'll create an issue to track general 32-bit support.

Oct 14 '19 18:10 woodruffw

To be more explicit here: we should prioritize syscalls of interest like those in gVisor:

https://github.com/google/gvisor/blob/add40fd6ad4c136bc17d1f243ec199c7bf37fa0b/pkg/sentry/syscalls/linux/linux64.go

Mar 06 '20 22:03 woodruffw