Re: (interposers): How to workaround the "strong symbols" problem?

On Sun, 19 Jan 2025 16:04:33 +0000
Richard Kettlewell <invalid@invalid.invalid> wibbled:

Marcel Mueller <news.5.maazl@spamgourmet.org> writes:

Am 18.01.25 um 01:42 schrieb Kenny McCormack:

Right.  It seems to boil down to:
     You can't interpose a syscall.
I.e., so if a library function calls the syscall directly (rather
than going through the Glibc wrapper), you can't interpose it.  This
is, of course, as it should be.

>
Hmm, it may be related to optimizations. Assuming the openat call is
inlined in another compilation unit there is no option to change this
at link time.

>
Inlining and compiler optimization aren’t relevant here.
>
“System call” can mean two things:
>
1) The actual transfer to the kernel, via an instruction such as SYSCALL
  (x86) or SVC (Arm). This is what appears in strace.

On a slight tangent, does anyone know of a good reference for how to use
the ptrace() call on Linux? The man page is somewhat obtuse.