6.2-rc7 fails building on Talos II: memory.c:(.text+0x2e14): undefined reference to `hash__tlb_flush'

[Erhard F.]

Just noticed a build failure on 6.2-rc7 for my Talos 2 (.config attached):

 # make
  CALL    scripts/checksyscalls.sh
  UPD     include/generated/utsversion.h
  CC      init/version-timestamp.o
  LD      .tmp_vmlinux.kallsyms1
ld: ld: DWARF error: could not find abbrev number 6
mm/memory.o: in function `unmap_page_range':
memory.c:(.text+0x2e14): undefined reference to `hash__tlb_flush'
ld: memory.c:(.text+0x2f8c): undefined reference to `hash__tlb_flush'
ld: ld: DWARF error: could not find abbrev number 3117
mm/mmu_gather.o: in function `tlb_remove_table':
mmu_gather.c:(.text+0x584): undefined reference to `hash__tlb_flush'
ld: mmu_gather.c:(.text+0x6c4): undefined reference to `hash__tlb_flush'
ld: mm/mmu_gather.o: in function `tlb_flush_mmu':
mmu_gather.c:(.text+0x80c): undefined reference to `hash__tlb_flush'
ld: mm/mmu_gather.o:mmu_gather.c:(.text+0xbe0): more undefined references to `hash__tlb_flush' follow
make[1]: *** [scripts/Makefile.vmlinux:35: vmlinux] Fehler 1
make: *** [Makefile:1264: vmlinux] Error 2

As 6.2-rc6 was good on this machine I did a quick bisect which revealed this commit:

 # git bisect bad
1665c027afb225882a5a0b014c45e84290b826c2 is the first bad commit
commit 1665c027afb225882a5a0b014c45e84290b826c2
Author: Michael Ellerman <mpe at ellerman.id.au>
Date:   Tue Jan 31 22:14:07 2023 +1100

    powerpc/64s: Reconnect tlb_flush() to hash__tlb_flush()
    
    Commit baf1ed24b27d ("powerpc/mm: Remove empty hash__ functions")
    removed some empty hash MMU flushing routines, but got a bit overeager
    and also removed the call to hash__tlb_flush() from tlb_flush().
    
    In regular use this doesn't lead to any noticable breakage, which is a
    little concerning. Presumably there are flushes happening via other
    paths such as arch_leave_lazy_mmu_mode(), and/or a bit of luck.
    
    Fix it by reinstating the call to hash__tlb_flush().
    
    Fixes: baf1ed24b27d ("powerpc/mm: Remove empty hash__ functions")
    Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
    Link: https://lore.kernel.org/r/20230131111407.806770-1-mpe@ellerman.id.au

 arch/powerpc/include/asm/book3s/64/tlbflush.h | 2 ++
 1 file changed, 2 insertions(+)


Regards,
Erhard
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