On Tue, Sep 28, 2021 at 5:42 PM Arnd Bergmann [off-list ref] wrote:

From: Arnd Bergmann <arnd@arndb.de>

On BE32 kernels, the __opcode_to_mem_thumb32() interface is intentionally
not defined, but it is referenced whenever runtime patching is enabled
for the kernel, which may be for ftrace, jump label, kprobes or kgdb:

arch/arm/kernel/patch.c: In function '__patch_text_real':
arch/arm/kernel/patch.c:94:32: error: implicit declaration of function '__opcode_to_mem_thumb32' [-Werror=implicit-function-declaration]
   94 |                         insn = __opcode_to_mem_thumb32(insn);
      |                                ^~~~~~~~~~~~~~~~~~~~~~~

Since BE32 kernels never run Thumb2 code, we never end up using the
result of this call, so providing an extern declaration without
a definition makes it build correctly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Looks good to me!
Reviewed-by: Linus Walleij <redacted>

Yours,
Linus Walleij

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