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SubjectRe: [RFC] Force build error on undefined symbols
Russell King wrote:
> Hi,
>
> I've checked the date, and it isn't April Fools day. I wish it was
> though.
>
> It appears that all binutils versions for ARM which are capable of
> building 2.6 kernels which have been tested so far contain a serious
> bug - it is possible to successfully link an object and still have
> various symbols undefined. Currently, these binutils have been
> tested on ARM (as cross-compilers and/or native) and found wanting:
>
> GNU assembler 2.13.90.0.18 20030206
> GNU assembler 2.14 20030612
> GNU assembler 2.14.90 20031229
> GNU ld version 2.14.90.0.7 20031029 Debian GNU/Linux
> Assembleur GNU 2.15.90.0.1 20040303
>
> So far, we have discovered two cases:
>
> 1. When building a certain file, an undefined symbolic constant
> (TI_USED_CP) ended up in the symbol table without a relocation,
> and the value the assembler decided to use was '0'. The effect
> of this is that we ended up setting bits in thread_info->flags.
>
> This appears to be a binutils "as" error.
>
> 2. When building the decompressor for ARM kernels, GCC appears to
> inexplicably emit ".global" directives for symbols not defined
> in the files being built, even though the symbols themselves are
> not actually used. I'm not sure whether this is a real bug;
> binutils on x86 appears to accept and link such objects.
>
> In both cases, the linker successfully created executable programs
> which ran. In the first case, it is a silent error; the kernel had
> been linked, and able to run, but the program is not correct.
>
> Obviously, the one true correct solution is to fix the toolchain and
> upgrade to the latest version. However, since we have potentially
> multiple binutils versions spread across more than a year affected,
> I think we need to detect such errors as well.
>
> Therefore, I propose the following patch to detect undefined symbols
> in the final image and force an error if this is the case.
>
> Comments?

How about adding --no-undefined to LDFLAGS_vmlinux instead?

--
Brian Gerst
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