user/sven/linux.git/kernel/module/kallsyms.c, branch next/HEAD

kallsyms: delta-compress lineinfo tables for ~2.7x size reduction

2026-04-08T23:26:44Z

Replace the flat uncompressed parallel arrays (lineinfo_addrs[], lineinfo_file_ids[], lineinfo_lines[]) with a block-indexed, delta-encoded, ULEB128 varint compressed format. The sorted address array has small deltas between consecutive entries (typically 1-50 bytes), file IDs have high locality (delta often 0, same file), and line numbers change slowly. Delta-encoding followed by ULEB128 varint compression shrinks most values from 4 bytes to 1. Entries are grouped into blocks of 64. A small uncompressed block index (first addr + byte offset per block) enables O(log(N/64)) binary search, followed by sequential decode of at most 64 varints within the matching block. All decode state lives on the stack -- zero allocations, still safe for NMI/panic context. Measured on a defconfig+debug x86_64 build (3,017,154 entries, 4,822 source files, 47,144 blocks): Before (flat arrays): lineinfo_addrs[] 12,068,616 bytes (u32 x 3.0M) lineinfo_file_ids[] 6,034,308 bytes (u16 x 3.0M) lineinfo_lines[] 12,068,616 bytes (u32 x 3.0M) Total: 30,171,540 bytes (28.8 MiB, 10.0 bytes/entry) After (block-indexed delta + ULEB128): lineinfo_block_addrs[] 188,576 bytes (184 KiB) lineinfo_block_offsets[] 188,576 bytes (184 KiB) lineinfo_data[] 10,926,128 bytes (10.4 MiB) Total: 11,303,280 bytes (10.8 MiB, 3.7 bytes/entry) Savings: 18.0 MiB (2.7x reduction) Booted in QEMU and verified with SysRq-l that annotations still work: default_idle+0x9/0x10 (arch/x86/kernel/process.c:767) default_idle_call+0x6c/0xb0 (kernel/sched/idle.c:122) do_idle+0x335/0x490 (kernel/sched/idle.c:191) cpu_startup_entry+0x4e/0x60 (kernel/sched/idle.c:429) rest_init+0x1aa/0x1b0 (init/main.c:760) Assisted-by: Claude:claude-opus-4-6 Link: https://lkml.kernel.org/r/20260322131543.971079-4-sashal@kernel.org Signed-off-by: Sasha Levin Suggested-by: Juergen Gross Cc: Geert Uytterhoeven Cc: Greg Kroah-Hartman Cc: Helge Deller Cc: James Bottomley Cc: Jonathan Corbet Cc: Kees Cook Cc: Laurent Pinchart Cc: Luis Chamberalin Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Peter Zijlstra Cc: Petr Mladek Cc: Petr Pavlu Cc: Randy Dunlap Cc: Richard Weinberger Cc: Steven Rostedt Cc: Thorsten Leemhuis Signed-off-by: Andrew Morton

kallsyms: extend lineinfo to loadable modules

2026-04-08T23:26:44Z

Add CONFIG_KALLSYMS_LINEINFO_MODULES, which extends the CONFIG_KALLSYMS_LINEINFO feature to loadable kernel modules. At build time, each .ko is post-processed by scripts/gen-mod-lineinfo.sh (modeled on gen-btf.sh) which runs scripts/gen_lineinfo --module on the .ko, generates a .mod_lineinfo section containing a compact binary table of .text-relative offsets, file IDs, line numbers, and filenames, and embeds it back into the .ko via objcopy. At runtime, module_lookup_lineinfo() performs a binary search on the module's .mod_lineinfo section, and __sprint_symbol() calls it for addresses that fall within a module. The lookup is NMI/panic-safe (no locks, no allocations) — the data lives in read-only module memory and is freed automatically when the module is unloaded. The gen_lineinfo tool gains --module mode which: - Uses .text section address as base (ET_REL files have no _text symbol) - Filters entries to .text-only (excludes .init.text/.exit.text) - Handles libdw's ET_REL path-doubling quirk in make_relative() - Outputs a flat binary-format section instead of named global symbols Per-module overhead is approximately 10 bytes per DWARF line entry. Assisted-by: Claude:claude-opus-4-6 Link: https://lkml.kernel.org/r/20260322131543.971079-3-sashal@kernel.org Signed-off-by: Sasha Levin Cc: Geert Uytterhoeven Cc: Greg Kroah-Hartman Cc: Helge Deller Cc: James Bottomley Cc: Jonathan Corbet Cc: Juegren Gross Cc: Kees Cook Cc: Laurent Pinchart Cc: Luis Chamberalin Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Peter Zijlstra Cc: Petr Mladek Cc: Petr Pavlu Cc: Randy Dunlap Cc: Richard Weinberger Cc: Steven Rostedt Cc: Thorsten Leemhuis Signed-off-by: Andrew Morton

module: add helper function for reading module_buildid()

2026-01-21T03:44:22Z

Add a helper function for reading the optional "build_id" member of struct module. It is going to be used also in ftrace_mod_address_lookup(). Use "#ifdef" instead of "#if IS_ENABLED()" to match the declaration of the optional field in struct module. Link: https://lkml.kernel.org/r/20251128135920.217303-4-pmladek@suse.com Signed-off-by: Petr Mladek Reviewed-by: Daniel Gomez Reviewed-by: Petr Pavlu Cc: Aaron Tomlin Cc: Alexei Starovoitov Cc: Daniel Borkman Cc: John Fastabend Cc: Kees Cook Cc: Luis Chamberalin Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Sami Tolvanen Cc: Steven Rostedt (Google) Signed-off-by: Andrew Morton

module: Use RCU in all users of __module_address().

2025-03-10T10:54:45Z

__module_address() can be invoked within a RCU section, there is no requirement to have preemption disabled. Replace the preempt_disable() section around __module_address() with RCU. Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250108090457.512198-15-bigeasy@linutronix.de Signed-off-by: Petr Pavlu

module: Use RCU in module_kallsyms_on_each_symbol().

2025-03-10T10:54:44Z

module::kallsyms can be accessed under RCU assumption. Use rcu_dereference() to access module::kallsyms. Update callers. Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250108090457.512198-9-bigeasy@linutronix.de Signed-off-by: Petr Pavlu

module: Use RCU in __find_kallsyms_symbol_value().

2025-03-10T10:54:44Z

module: Use RCU in find_module_all().

2025-03-10T10:54:44Z

The modules list and module::kallsyms can be accessed under RCU assumption. Remove module_assert_mutex_or_preempt() from find_module_all() so it can be used under RCU protection without warnings. Update its callers to use RCU protection instead of preempt_disable(). Cc: Jiri Kosina Cc: Joe Lawrence Cc: Josh Poimboeuf Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Miroslav Benes Cc: Petr Mladek Cc: Steven Rostedt Cc: linux-trace-kernel@vger.kernel.org Cc: live-patching@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra (Intel) Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20250108090457.512198-7-bigeasy@linutronix.de Signed-off-by: Petr Pavlu

module: Use RCU in module_get_kallsym().

2025-03-10T10:54:44Z

The modules list and module::kallsyms can be accessed under RCU assumption. Iterate the modules with RCU protection, use rcu_dereference() to access the kallsyms pointer. Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250108090457.512198-6-bigeasy@linutronix.de Signed-off-by: Petr Pavlu

module: Use RCU in find_kallsyms_symbol().

2025-03-10T10:54:44Z

The modules list and module::kallsyms can be accessed under RCU assumption. Use rcu_dereference() to reference the kallsyms pointer in find_kallsyms_symbol(). Use a RCU section instead of preempt_disable in callers of find_kallsyms_symbol(). Keep the preempt-disable in module_address_lookup() due to __module_address(). Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250108090457.512198-5-bigeasy@linutronix.de Signed-off-by: Petr Pavlu

module: Use proper RCU assignment in add_kallsyms().

2025-03-10T10:54:44Z

add_kallsyms() assigns the RCU pointer module::kallsyms and setups the structures behind it which point to init-data. The module was not published yet, nothing can see the kallsyms pointer and the data behind it. Also module's init function was not yet invoked. There is no need to use rcu_dereference() here, it is just to keep checkers quiet. The whole RCU read section is also not needed. Use a local kallsyms pointer and setup the data structures. Assign that pointer to the data structure at the end via rcu_assign_pointer(). Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250108090457.512198-4-bigeasy@linutronix.de Signed-off-by: Petr Pavlu