On Mon, Jul 15, 2019 at 01:16:48PM -0700, H.J. Lu wrote: > On Mon, Jul 15, 2019 at 3:35 AM Thomas Gleixner <[email protected]> wrote: > > > > On Mon, 15 Jul 2019, Thomas Gleixner wrote: > > > On Mon, 15 Jul 2019, Mike Lothian wrote: > > > > That build failure is from the current tip of Linus's tree > > > > If the fix is in, then it hasn't fixed the issue > > > > > > The reverted commit caused a build fail with gold as well. Let me stare at > > > your issue. > > > > So with gold the build fails in the reloc tool complaining about that > > relocation: > > > > Invalid absolute R_X86_64_32S relocation: __end_of_kernel_reserve > > > > The commit does: > > > > +extern char __end_of_kernel_reserve[]; > > + > > > > void __init setup_arch(char **cmdline_p) > > { > > + /* > > + * Reserve the memory occupied by the kernel between _text and > > + * __end_of_kernel_reserve symbols. Any kernel sections after the > > + * __end_of_kernel_reserve symbol must be explicitly reserved with a > > + * separate memblock_reserve() or they will be discarded. > > + */ > > memblock_reserve(__pa_symbol(_text), > > - (unsigned long)__bss_stop - (unsigned long)_text); > > + (unsigned long)__end_of_kernel_reserve - (unsigned > > long)_text); > > > > So it replaces __bss_stop with __end_of_kernel_reserve here. > > > > --- a/arch/x86/kernel/vmlinux.lds.S > > +++ b/arch/x86/kernel/vmlinux.lds.S > > @@ -368,6 +368,14 @@ SECTIONS > > __bss_stop = .; > > } > > > > + /* > > + * The memory occupied from _text to here, __end_of_kernel_reserve, > > is > > + * automatically reserved in setup_arch(). Anything after here must > > be > > + * explicitly reserved using memblock_reserve() or it will be > > discarded > > + * and treated as available memory. > > + */ > > + __end_of_kernel_reserve = .; > > > > And from the linker script __bss_stop and __end_of_kernel_reserve are > > exactly the same. From System.map (of a successful ld build): > > > > ffffffff82c00000 B __brk_base > > ffffffff82c00000 B __bss_stop > > ffffffff82c00000 B __end_bss_decrypted > > ffffffff82c00000 B __end_of_kernel_reserve > > ffffffff82c00000 B __start_bss_decrypted > > ffffffff82c00000 B __start_bss_decrypted_unused > > > > So how on earth can gold fail with that __end_of_kernel_reserve change? > > > > For some unknown reason it turns that relocation into an absolute > > one. That's clearly a gold bug^Wfeature and TBH, I'm more than concerned > > about that kind of behaviour. > > > > If we just revert that commit, then what do we achieve? We paper over the > > underlying problem, which is not really helping anything. > > > > Aside of that gold still fails to build the X32 VDSO and it does so for a > > very long time.... > > > > Until we really understand what the problem is, this stays as is. > > > > @H.J.: Any insight on that? > > > > Since building a workable kernel for different kernel configurations isn't a > requirement for gold, I don't recommend gold for kernel.
Um, it worked before this commit, and now it doesn't. "Some" companies are using gold for linking the kernel today... thanks, greg k-h
