Date: Mon, 26 Sep 2022 15:38:33 -0700 From: Colin Cross <ccross@...roid.com> To: Colin Cross <ccross@...roid.com>, musl@...ts.openwall.com, Ryan Prichard <rprichard@...gle.com> Subject: Re: Running musl executables without a preinstalled dynamic linker On Tue, Aug 23, 2022 at 1:18 AM Szabolcs Nagy <nsz@...t70.net> wrote: > > * Colin Cross <ccross@...roid.com> [2022-08-22 17:22:06 -0700]: > > On Sat, Aug 20, 2022 at 2:43 AM Szabolcs Nagy <nsz@...t70.net> wrote: > > > i would not use Scrt1.o though, the same toolchain should be > > > usable for normal linking and relinterp linking, just use a > > > different name like Xcrt1.o. > > > > Is there some way to get gcc/clang to use Xcrt1.o without using > > -nostdlib and passing all the crtbegin/end objects manually? > > this requires compiler changes (new cmdline flag) but then i think > the code is upstreamable. I've used relinterp.o for now, and selected instead of Scrt1.o in musl-gcc.specs and ld.musl-clang. > > > > i would make Xcrt1.o self-contained and size optimized: it only > > > runs at start up, this is a different requirement from the -O3 > > > build of normal string functions. and then there is no dependency > > > on libc internals (which may have various instrumentations that > > > does not work in Xcrt1.o). > > > > Doesn't this same logic apply to most of the code in dynlink.c? My > > main worry with a self contained implementation is that it requires > > reimplementations of various string functions that are easy to get > > wrong. The current prototype reuses the C versions of musl's string > > functions, but implements its own syscall wrappers to avoid > > interactions with musl internals like errno. > > dynlink is in libc.so so it can use code from there. > > but moving libc code into the executable has different constraints. > so you will have to make random decisions that string functions are > in but errno is out, wrt which libc internal makes sense in the exe. > > i would just keep a separate implementation (or at least compile > the code separately). string functions are easy to implement if > you dont try to optimize them imo. then you have full control over > what is going on in the exe entry code. I left the reimplementations of string functions and syscalls as suggested. Patch attached.
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