kallsyms: strip LTO suffixes from static functions

kallsyms: strip LTO suffixes from static functions

Similar to:
commit 8b8e6b5d3b01 ("kallsyms: strip ThinLTO hashes from static
functions")

It's very common for compilers to modify the symbol name for static
functions as part of optimizing transformations. That makes hooking
static functions (that weren't inlined or DCE'd) with kprobes difficult.

LLVM has yet another name mangling scheme used by thin LTO.

Combine handling of the various schemes by truncating after the first
'.'.  Strip off these suffixes so that we can continue to hook such
static functions.  Clang releases prior to clang-13 would use '$'
instead of '.'

Link: https://reviews.llvm.org/rGc6e5c4654bd5045fe22a1a52779e48e2038a404c
Reported-by: KE.LI(Lieke) <[email protected]>
Suggested-by: Nathan Chancellor <[email protected]>
Suggested-by: Padmanabha Srinivasaiah <[email protected]>
Suggested-by: Sami Tolvanen <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Reviewed-by: Fangrui Song <[email protected]>
Reviewed-by: Sami Tolvanen <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]