Date: Wed, 10 Jun 2020 06:39:35 -0400 From: Jeffrey Walton <noloader@...il.com> To: musl@...ts.openwall.com, Norbert Lange <nolange79@...il.com> Subject: Re: Mark stack as non-executable in asm On Wed, Jun 10, 2020 at 6:31 AM Szabolcs Nagy <nsz@...t70.net> wrote: > > * Norbert Lange <nolange79@...il.com> [2020-06-10 11:24:04 +0200]: > > I did borrow some assembler files to avoid having to link against > > (any) libc. That was for building a DSO, ultimately loaded via glibc. > > The effect was that glibc did change the protection of all stacks to > > be executable. > > > > Would you consider adding the line  > > .section .note.GNU-stack, "", %progbits > > to assembly files? > > > > I know this is not a musl bug, and I can easily add the lines myself. > > musl build system (just like other libcs i know of) > pass -noexecstack to the assembler so if you build > the asm files as part of libc the object files should > have the marking, if you build outside of libc i > think it's your responsibility to add the note > (either to the asm or via the -Wa,-noexecstack flag) > > readelf -lW libfoo.so | grep GNU_STACK > > is one way to verify that everything has the note. It may be worth mentioning, according to the Binutil folks, the stack size has to be 0. A non-0 stack size means executable stacks are in effect. In the case of non-0, I believe the loader is responsible for loss of the nx-stack. Jeff
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