On Thu, Mar 21, 2024 at 8:48 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > On Thu, Mar 21, 2024 at 12:52:16PM -0700, Max Filippov wrote: > > On Thu, Mar 21, 2024 at 10:05 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > What's the best way to test this? (Is there a qemu setup I can use to > > > see the before/after of AT_EXECFN?) > > > > I put a readme with the steps to build such system here: > > http://jcmvbkbc.org/~dumb/tmp/202403211236/README > > it uses a prebuilt rootfs image and a 6.8 kernel branch with two > > patches on top of it: one adds a dts and a defconfig and the other > > is this fix. The rootfs boots successfully with this fix, but panics > > if this fix is removed. > > Does musl have something like the LD_SHOW_AUXV env variable. With glibc, > I usually explore auxv like so: > > $ LD_SHOW_AUXV=1 uname -a | grep EXECFN > AT_EXECFN: /usr/bin/uname I couldn't find anything like that in either musl or uClibc-ng. So I updated the above rootfs and put the following program into it as /bin/test-auxv: #include <stdio.h> #include <sys/auxv.h> int main() { unsigned long p = getauxval(AT_EXECFN); fprintf(stderr, "AT_EXECFN: 0x%lx\n", p); if (p) fprintf(stderr, "%s\n", (const char *)p); return 0; } While looking at it I also noticed that /proc/<pid>/auxv is empty on NOMMU, looks like there will be yet another fix for that. -- Thanks. -- Max
