Hi Paul and Tom,
Thanks a ton for helping out.
I have almost made my setup work.
I try to install libseccomp using release tarball (libseccomp-2.3.3.tar.gz)
https://github.com/seccomp/libseccomp/releases
But even after successful installation, I run into following error at runtime:
"error while loading shared libraries: libseccomp.so.2: cannot open shared
object file: No such file or directory"
I did following to install
./configure
make
make install
Is there any build time configuration that i might be missing.
This i don't encounter when I install libseccomp from debian package using
apt-get.
On Wednesday, May 23, 2018 at 2:01:23 AM UTC+5:30, Paul Moore wrote:
> Hello,
>
> My apologies, I didn't look close enough at your original example
> code, but Tom is correct regarding SCMP_SYS (thanks Tom!).
>
> As far as seccomp_syscall_resolve_name() is concerned, no, it does not
> rewrite the syscall number for the multiplexed syscalls; if run on
> 32-bit x86 seccomp_syscall_resolve_name("socket") will return -101
> (negative syscall numbers are special pseudo-syscall numbers used by
> libseccomp when the syscall does not exist for a given ABI. If you
> want libseccomp to rewrite the syscall number to a valid syscall you
> should use seccomp_syscall_resolve_name_rewrite();
> seccomp_syscall_resolve_name_rewrite(SCMP_ARCH_X86, "socket") returns
> 102 which is the syscall number for socketcall() on 32-bit x86.
>
> On Tue, May 22, 2018 at 1:33 PM, Amit Malav <[email protected]> wrote:
> > Hi,
> > Thanks for clarifying.
> > I have changed that line of code to
> > seccomp_rule_add(ctx, SCMP_ACT_ALLOW,
> > seccomp_syscall_resolve_name(argv[iterator]), 0)
> > It seems to do the job.
> > Although on man page for seccomp_syscall_resolve_name, it is mentioned
> > "seccomp_syscall_resolve_name_rewrite() functions resolve the commonly used
> > syscall name to the syscall number used by the kernel and the rest of the
> > libseccomp API".
> > Does it mean that this method does not resolve to correct syscall number
> > for multiplexed syscall, like socketcall(2) or ipc(2) on x86 ?
> >
> > On Tuesday, May 22, 2018 at 10:56:09 PM UTC+5:30, Tom Hromatka wrote:
> >> On 05/21/2018 09:01 PM, Amit Malav wrote:
> >>
> >> > Hi Pautl.
> >> > Thanks for the swift response.
> >> > But i'm getting following error while compiling above code.
> >> >
> >> > #gcc test-seccomp.c -l seccomp -o seccomp
> >> >
> >> > In file included from test-seccomp.c:6:0:
> >> > test-seccomp.c: In function ‘main’:
> >> > test-seccomp.c:37:51: error: ‘__NR_argv’ undeclared (first use in this
> >> > function)
> >> > seccomp_rule_add(ctx, SCMP_ACT_ALLOW,
> >> > SCMP_SYS(argv[iterator]), 0);
> >> > ^
> >> > test-seccomp.c:37:51: note: each undeclared identifier is reported only
> >> > once for each function it appears in
> >> >
> >> > Am i doing something wrong here? Can this be achieved differently?
> >>
> >> I admit I didn't look through the entire thread, so my apologies
> >> up front.
> >>
> >> SCMP_SYS() is a helper macro that converts syscall names (read,
> >> write, open, mmap, etc.) into their respective numbers for that
> >> particular architecture (0, 1, 2, 9, etc. for the aforementioned
> >> list on x86_64).
> >>
> >> /**
> >> * Convert a syscall name into the associated syscall number
> >> * @param x the syscall name
> >> */
> >> #define SCMP_SYS(x) (__NR_##x)
> >>
> >> Passing argv[] into SCMP_SYS will be stringified into __NR_argv[]
> >> which is not a valid syscall number.
> >>
> >> Regards.
> >>
> >> Tom
> >
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>
>
> --
> paul moore
> www.paul-moore.com
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