My assumption here was that applications that are aware of the new API will always provide three parameters, while older applications will continue calling the syscall with two. I can't think of a situation/architecture where this will break anything. Thanks, Peter On Tue, Nov 17, 2020 at 10:44 AM Florian Weimer <fw@xxxxxxxxxxxxx> wrote: > > * Segher Boessenkool: > > > But this isn't variadic in the sense of "..." -- on Power that always > > passes the unspecified arguments in memory, while in this case it just > > passes in either two or three registers. I don't know any arg where > > that would not work, given the Linux system call restrictions. > > > > This is similar to the "open" system call. > > Exactly. You cannot call the open function through a non-variadic > function pointer. I've seen it cause stack corruption in practice: > > commit c7774174beffe9a8d29dd4fb38bbed43ece1cecd > Author: Andreas Schneider <asn@xxxxxxxxx> > Date: Wed Aug 2 13:21:59 2017 +0200 > > swrap: Fix prototype of open[64] to prevent segfault on ppc64le > > The calling conventions for vaarg are different on ppc64le. The patch > fixes segfaults on that platform. > > Thanks to Florian Weimer who helped debugging it! > > Signed-off-by: Andreas Schneider <asn@xxxxxxxxx> > Reviewed-by: Stefan Metzmacher <metze@xxxxxxxxx> > > <https://git.samba.org/?p=socket_wrapper.git;a=commitdiff;h=c7774174beffe> > > It is possible to implement the open function in such a way that it > does not have this problem (simply do not use the parameter save area, > using assembler if necessary), but it's another obscure step that libc > implementers would have to take.
