Kernel 5.2RC (Release Candidate) series

[Doug S]

Good news - Linus has dubbed 5.2 "Bobtail Squid" & pushed it out of the nest.
Bad news - Today's build has failed for both AMD64 & i386.

Interesting. I am still on kernel 5.2-rc5, due to some continuing testing. I see the daily build worked until yesterday. I'll try to compile it myself shortly.

EDIT 1: Looks like a messed up kernel configuration file to me.
EDIT 2: Reported on kernel IRC channel. result: "this is a bug introduced by the compiler hardening options being turned on by default"
EDIT 3: Compiles fine for me, probably because I am using an old version of the compiler.
EDIT 4: Bug report

[IanW]

There is more bad news however.
Phoronix is reporting that anything later than 18.04LTS won't boot on the new Ryzen 3000 CPU's.
There is much discussion of what the cause may be in the comments.

[Doug S]

There is more bad news however.
Phoronix is reporting that anything later than 18.04LTS won't boot on the new Ryzen 3000 CPU's.
There is much discussion of what the cause may be in the comments.

Yes, but it is my understanding (without looking at your link) that the issue is a systemd problem. I saw a bug report just yesterday about it, with a patch. I'll see if I can find it again. Oh, it was while I was still on the kernel channel on IRC. See here.

[IanW]

Yes, but it is my understanding (without looking at your link) that the issue is a systemd problem. I saw a bug report just yesterday about it, with a patch. I'll see if I can find it again. Oh, it was while I was still on the kernel channel on IRC. See here.

Thanks.

[Doug S]

For users wanting to compile the mainline 5.2 kernel for themselves, and with the newer compiler included with 19.10 do this:

doug@serv-ee:~/temp-k-git/linux$ git diff
diff --git a/Makefile b/Makefile
index 3e4868a6498b..d8ccc47215be 100644
--- a/Makefile
+++ b/Makefile
@@ -630,8 +630,8 @@ ifdef CONFIG_FUNCTION_TRACER
   CC_FLAGS_FTRACE := -pg
 endif

-RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register
-RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register
+RETPOLINE_CFLAGS_GCC := -mindirect-branch=thunk-extern -mindirect-branch-register -fcf-protection=none
+RETPOLINE_VDSO_CFLAGS_GCC := -mindirect-branch=thunk-inline -mindirect-branch-register -fcf-protection=none
 RETPOLINE_CFLAGS_CLANG := -mretpoline-external-thunk
 RETPOLINE_VDSO_CFLAGS_CLANG := -mretpoline
 RETPOLINE_CFLAGS := $(call cc-option,$(RETPOLINE_CFLAGS_GCC),$(call cc-option,$(RETPOLINE_CFLAGS_CLANG)))

And it should then compile.
References:
https://bugs.launchpad.net/ubuntu/+s...9/+bug/1830961
https://www.spinics.net/lists/linux-.../msg22298.html
https://patchwork.kernel.org/patch/11037379/

[mrfelker]

Latest successful build for amd64 that I could find is https://kernel.ubuntu.com/~kernel-pp...ine/v5.2-rc7// This is 2 weeks old. Never seen this before.

[IanW]

A Phoronix comment says the newer kernels use the -mindirect-branch flag to deal with retpolines.
This is not compatible with Ubuntu's chosen fcf-protection flag.

See Launchpad bug #1830961

[IanW]

UPDATE - I got a 5.2.0-8 kernel yesterday through the normal update channels.

[Doug S]

Latest successful build for amd64 that I could find is https://kernel.ubuntu.com/~kernel-pp...ine/v5.2-rc7// This is 2 weeks old. Never seen this before.

You can also see people on the bug report asking for the mainline build to be fixed. However it has to wait for the fix, which has been picked up, to make it into the upstream mainline, which it hasn't yet. It'll first appear in the dailies, but not as of today. Hopefully by kernel 5.3-rc1.

[Doug S]

You can also see people on the bug report asking for the mainline build to be fixed. However it has to wait for the fix, which has been picked up, to make it into the upstream mainline, which it hasn't yet. It'll first appear in the dailies, but not as of today. Hopefully by kernel 5.3-rc1.

The patch has been merged into upstream mainline, so the Ubuntu daily for July 21st should compile properly.