Date: Fri, 19 Jun 2015 10:35:39 -0400 From: Rich Felker <dalias@...c.org> To: Ralf Baechle <ralf@...ux-mips.org> Cc: Matthias Schiffer <mschiffer@...verse-factory.net>, musl@...ts.openwall.com, linux-mips@...ux-mips.org, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: musl-libc/MIPS: detached thread exit broken since kernel commit 46e12c07b On Fri, Jun 19, 2015 at 12:06:26PM +0200, Ralf Baechle wrote: > On Thu, Jun 18, 2015 at 10:50:32PM -0400, Rich Felker wrote: > > > This is kernel ABI breakage that should be fixed -- people running old > > kernel versions with old musl binaries might suffer a regression when > > upgrading, and perhaps more importantly the failure mode is just > > really bad. But I think we can also work around it on the userspace > > side in musl by pointing the stack pointer at some rodata (or even at > > pc, e.g. copying $25 to $sp) before making the syscall. > > Just to be on the safe side, make sure it is something that's readable. Core > might me mapped execute-only, that is not readable and that is a feature > which the affected kernels do support on suitable hardware. How would that happen? Do you have ELF files with 3 PT_LOAD segments? Normally there are two and their permissions are r-x and rw-. Rich
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