linux-kernel - Remaining randconfig objtool warnings, linux-next-20200428

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Date:   Tue, 28 Apr 2020 16:49:15 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Remaining randconfig objtool warnings, linux-next-20200428

I noticed the number of objtool warnings in randconfig kernels have gone down
 recently, maybe it's possible to eliminate the remaining ones?

Here are the ones I ran into recently, using gcc-9.3:

==> build/x86/0x3D2B5D6D_defconfig/log <==
arch/x86/kvm/vmx/vmx.o: warning: objtool:
vmx_handle_exit_irqoff()+0x24: unreachable instruction

==> build/x86/0xE0F2ACFF_defconfig/log <==
kernel/time/posix-stubs.o: warning: objtool:
__x64_sys_timer_create()+0x23: sibling call from callable instruction
with modified stack frame

==> build/x86/0xFD7B7323_defconfig/log <==
arch/x86/entry/entry_64.o: warning: objtool: .entry.text+0x991:
unreachable instruction

==> build/x86/0x2EA4CE4F_defconfig/log <==
kernel/kcov.o: warning: objtool: write_comp_data()+0x1b: call to
check_kcov_mode() with UACCESS enabled
kernel/kcov.o: warning: objtool: __sanitizer_cov_trace_pc()+0x15: call
to check_kcov_mode() with UACCESS enabled

==> build/x86/0x500B1B82_defconfig/log <==
kernel/bpf/core.o: warning: objtool: ___bpf_prog_run()+0x1269: call
without frame pointer save/setup

==> build/x86/0x7942F24A_defconfig/log <==
samples/ftrace/ftrace-direct.o: warning: objtool: .text+0x0:
unreachable instruction
samples/ftrace/ftrace-direct-too.o: warning: objtool: .text+0x0:
unreachable instruction
samples/ftrace/ftrace-direct-modify.o: warning: objtool: .text+0x0:
unreachable instruction

I've uploaded the .config and .o files for each one to
https://drive.google.com/open?id=0B_XQwQ5KlfJAbUtrTVJaRmJIZUk
Let me know if you need any additional information.

Note that I used a modified linux-next tree (including many build
fixes) for creating
these, some of them may not actually happen with mainline or unpatched
linux-next
kernels.

        Arnd