linux-kernel - [PATCH v2 0/3] Fix kallsyms with CONFIG_LTO

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Message-ID: <20240802210836.2210140-1-song@kernel.org>
Date: Fri,  2 Aug 2024 14:08:32 -0700
From: Song Liu <song@...nel.org>
To: live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Cc: jpoimboe@...nel.org,
	jikos@...nel.org,
	mbenes@...e.cz,
	pmladek@...e.com,
	joe.lawrence@...hat.com,
	nathan@...nel.org,
	morbo@...gle.com,
	justinstitt@...gle.com,
	mcgrof@...nel.org,
	thunder.leizhen@...wei.com,
	kees@...nel.org,
	kernel-team@...a.com,
	song@...nel.org,
	mmaurer@...gle.com,
	samitolvanen@...gle.com,
	mhiramat@...nel.org,
	rostedt@...dmis.org
Subject: [PATCH v2 0/3] Fix kallsyms with CONFIG_LTO_CLANG

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 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.

Changes v1 => v2:
1. Update the APIs to remove all .XXX suffixes (v1 only removes .llvm.*).
2. Rename the APIs as *_without_suffix. (Masami Hiramatsu)
3. Fix another user from kprobe. (Masami Hiramatsu)
4. Add tests for the new APIs in kallsyms_selftests.

v1: https://lore.kernel.org/live-patching/20240730005433.3559731-1-song@kernel.org/T/#u

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

 include/linux/kallsyms.h    | 14 ++++++
 kernel/kallsyms.c           | 88 +++++++++++++++++++++++++------------
 kernel/kallsyms_selftest.c  | 75 ++++++++++++++++++++++---------
 kernel/kprobes.c            |  6 ++-
 kernel/trace/trace_kprobe.c | 11 ++++-
 scripts/kallsyms.c          | 31 +------------
 scripts/link-vmlinux.sh     |  4 --
 7 files changed, 145 insertions(+), 84 deletions(-)

--
2.43.0