+++ Jessica Yu [10/08/20 11:25 +0200]:
+++ Mauro Carvalho Chehab [08/08/20 10:12 +0200]:
[snip]
Right now, what happens is:
# modprobe wlcore
modprobe: ERROR: could not insert 'wlcore': Exec format error
This seems to be failing for all modules, as doesn't show anything
probed.
Btw, IMO, it would be useful to have some pr_debug() infra in order to
explain why insmod is failing, or to have more error codes used there,
as nothing was printed at dmesg. That makes harder to debug issues
there. I ended losing a lot of time yesterday rebuilding the Kernel
and checking the FS, before deciding to add some printks inside the
Kernel ;-)
In order for modprobe to start working again, I had to apply this
dirty hack:
<hack>
diff --git a/kernel/module.c b/kernel/module.c
index 910a57640818..10d590dc48ad 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2051,11 +2051,12 @@ static int module_enforce_rwx_sections(Elf_Ehdr *hdr,
Elf_Shdr *sechdrs,
const unsigned long shf_wx = SHF_WRITE|SHF_EXECINSTR;
int i;
+#if 0
for (i = 0; i < hdr->e_shnum; i++) {
if ((sechdrs[i].sh_flags & shf_wx) == shf_wx)
return -ENOEXEC;
}
-
+#endif
return 0;
}
</hack>
[ I somehow munged the To: header in the last mail. Sorry about that,
it's fixed now. ]
All this hunk does it reject loading modules that have any sections
that have both the writable and executable flags. You're saying it's
happening for all modules on your setup - I am curious as to which
sections have both these flags - what does readelf -S tell you?
Hmm, I was not able to reproduce this with a cross-compiled kernel
using the attached config (gcc 9.3.0 with vanilla v5.8 kernel). I am
curious if the failing sections are also SHF_ALLOC - in that case, the
code is doing what it is intended to do, which is rejecting loading
any modules with writable and executable sections. If the problematic
sections are *not* SHF_ALLOC, then we might be able to work around
that by ignoring non-SHF_ALLOC sections as they are not copied to the
final module location anyway.
Jessica
