With CONFIG_LTO_CLANG, the compiler/linker adds .llvm.<hash> suffix to
local symbols to avoid duplications. Existing scripts/kallsyms sorts
symbols without .llvm.<hash> suffix. However, this causes quite some
issues later on. Some users of kallsyms, such as livepatch, have to match
symbols exactly; while other users, such as kprobe, would match symbols
without the suffix.

Address this by sorting full symbols (with .llvm.<hash>) at build time, and
split kallsyms APIs to explicitly match full symbols or without suffix.
Specifically, exiting APIs will match symbols exactly. Two new APIs are
added to match symbols with suffix. Use the new APIs in tracing/kprobes.

Song Liu (3):
  kallsyms: Do not cleanup .llvm.<hash> suffix before sorting symbols
  kallsyms: Add APIs to match symbol without .llmv.<hash> suffix.
  tracing/kprobes: Use APIs that matches symbols with .llvm.<hash>
    suffix

 include/linux/kallsyms.h    | 14 +++++++
 kernel/kallsyms.c           | 83 ++++++++++++++++++++++++++-----------
 kernel/kallsyms_selftest.c  | 22 +---------
 kernel/trace/trace_kprobe.c | 10 ++++-
 scripts/kallsyms.c          | 30 +-------------
 scripts/link-vmlinux.sh     |  4 --
 6 files changed, 83 insertions(+), 80 deletions(-)

--
2.43.0

On Mon, Jul 29, 2024 at 5:54 PM Song Liu <song@kernel.org> wrote:
>
> With CONFIG_LTO_CLANG, the compiler/linker adds .llvm.<hash> suffix to
> local symbols to avoid duplications. Existing scripts/kallsyms sorts
> symbols without .llvm.<hash> suffix. However, this causes quite some
> issues later on. Some users of kallsyms, such as livepatch, have to match
> symbols exactly; while other users, such as kprobe, would match symbols
> without the suffix.
>
> Address this by sorting full symbols (with .llvm.<hash>) at build time, and
> split kallsyms APIs to explicitly match full symbols or without suffix.
> Specifically, exiting APIs will match symbols exactly. Two new APIs are
> added to match symbols with suffix. Use the new APIs in tracing/kprobes.

Forgot to mention: This is to follow up the discussions in this thread:

https://lore.kernel.org/live-patching/20240605032120.3179157-1-song@kernel.org/T/#u

Thanks,
Song