Fix for objtool/module breakage
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Laura Abbott
parent
3a9b20b346
commit
e582bbd727
@ -602,6 +602,9 @@ Patch666: ccm-stack.patch
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# grabbed from mailing list
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Patch667: v3-Revert-tty-serial-pl011-add-ttyAMA-for-matching-pl011-console.patch
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# reported via IRC
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Patch668: objtool-fix.patch
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# END OF PATCH DEFINITIONS
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%endif
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153
objtool-fix.patch
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153
objtool-fix.patch
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@ -0,0 +1,153 @@
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From 898d20ca04d5a13dcca5483ed5213ad92fed88d3 Mon Sep 17 00:00:00 2001
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From: Josh Poimboeuf <jpoimboe@redhat.com>
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Date: Wed, 1 Mar 2017 00:05:04 -0600
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Subject: [PATCH] objtool fixes
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On Tue, Feb 28, 2017 at 05:55:11PM -0800, Linus Torvalds wrote:
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> Guys,
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> the recent 'objtool' pull request broke things.
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>
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> I haven't bisected it, but I'm pretty sure that this part is pure garbage:
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>
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> On Mon, Feb 27, 2017 at 11:53 PM, Ingo Molnar <mingo@kernel.org> wrote:
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> >
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> > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
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> > index e79f15f108a8..ad0118fbce90 100644
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> > --- a/arch/x86/kernel/vmlinux.lds.S
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> > +++ b/arch/x86/kernel/vmlinux.lds.S
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> > @@ -346,6 +346,7 @@ SECTIONS
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> > /DISCARD/ : {
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> > *(.eh_frame)
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> > *(__func_stack_frame_non_standard)
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> > + *(__unreachable)
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> > }
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> > }
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> >
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> > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
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> > index 0444b1336268..f457b520ead6 100644
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> > --- a/include/linux/compiler-gcc.h
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> > +++ b/include/linux/compiler-gcc.h
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> > @@ -195,6 +195,17 @@
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> > #endif
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> > #endif
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> >
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> > +#ifdef CONFIG_STACK_VALIDATION
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> > +#define annotate_unreachable() ({ \
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> > + asm("%c0:\t\n" \
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> > + ".pushsection __unreachable, \"a\"\t\n" \
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> > + ".long %c0b\t\n" \
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> > + ".popsection\t\n" : : "i" (__LINE__)); \
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> > +})
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> > +#else
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> > +#define annotate_unreachable()
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> > +#endif
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>
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> and I think the above is what breaks module loading for me right now
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> on my laptop.
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>
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> I get this during bootup:
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>
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> module: overflow in relocation type 10 val ffffffffc02afc81
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> module: 'nvme' likely not compiled with -mcmodel=kernel
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>
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> (and similar errors for other modules too), but those modules very
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> much *are* compiled with all the normal kernel build flags, including
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> -mcmodel=kernel.
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>
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> Now, relocation type 10 is R_X86_64_32, so the warning is very true:
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> that address would fit in a _signed_ 32-bit value, but that's
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> supposedly a 32-bit unsigned relocation.
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>
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> Trying to figure out what the hell is going on, I do:
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>
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> objdump -r nvme.ko | grep 64_32
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>
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> and what do I find? I find
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>
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> RELOCATION RECORDS FOR [__unreachable]:
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> OFFSET TYPE VALUE
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> 0000000000000000 R_X86_64_32 .text+0x0000000000000c81
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> 0000000000000004 R_X86_64_32 .text+0x0000000000000cb5
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> 0000000000000008 R_X86_64_32 .text+0x0000000000001a18
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> 000000000000000c R_X86_64_32 .text+0x0000000000001a36
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> 0000000000000010 R_X86_64_32 .text+0x0000000000001e38
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> 0000000000000014 R_X86_64_32 .text+0x0000000000001ec2
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> 0000000000000018 R_X86_64_32 .text+0x00000000000034e2
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> 000000000000001c R_X86_64_32 .text+0x0000000000003536
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>
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> and then when I look more closely (objdump --disassemble), I see that
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> the offset 000c81 in the module refers to this:
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>
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> 0000000000000c60 <nvme_admin_init_request>:
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> ....
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> c7f: 0f 0b ud2
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> c81: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
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>
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> so it very much looks like those relocations are still around on
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> modules, and so module loading fails.
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>
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> Anyway, those annotations are completely bogus anyway, it looks. You
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> guys should use relative offsets in order to be able to specify a
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> kernel address. So doing
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>
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> .long %c0
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>
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> is garbage - either it needs to be a .quad, or it needs to be relative
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> to the text section to fit in a .long.
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>
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> Hmm? Revert or fix, but please quickly...
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Yuck, sorry about that. Patch to fix it below.
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This also highlights another (minor) issue: the '__unreachable' section
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is meant to be a compile-time-only thing. It's supposed to be discarded
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at link time, but apparently that isn't happening for modules.
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I tried excluding it from linking with the .pushsection "e" flag, but no
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luck. I'll try to figure out how to fix that shortly.
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In the meantime, here's the fix you need. It now uses X86_64_64
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relocations.
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----
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From: Josh Poimboeuf <jpoimboe@redhat.com>
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Subject: [PATCH] objtool: fix __unreachable section relocation size
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Linus reported the following commit broke module loading on his laptop:
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d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
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It showed errors like the following:
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module: overflow in relocation type 10 val ffffffffc02afc81
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module: 'nvme' likely not compiled with -mcmodel=kernel
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The problem is that the __unreachable section addresses are stored using
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the '.long' asm directive, which isn't big enough for .text section
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relative kernel addresses. Use '.quad' instead.
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Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
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Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
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Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends")
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Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
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---
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include/linux/compiler-gcc.h | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
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index 76e28c2..91a77a5 100644
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--- a/include/linux/compiler-gcc.h
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+++ b/include/linux/compiler-gcc.h
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@@ -201,7 +201,7 @@
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#define annotate_unreachable() ({ \
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asm("%c0:\t\n" \
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".pushsection __unreachable, \"a\"\t\n" \
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- ".long %c0b\t\n" \
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+ ".quad %c0b\t\n" \
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".popsection\t\n" : : "i" (__LINE__)); \
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})
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#else
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--
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2.7.4
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