linux-stable.git/scripts/link-vmlinux.sh, branch v6.6.144

scripts/sorttable: Zero out weak functions in mcount_loc table

2026-07-04T11:42:21+00:00

[ Upstream commit ef378c3b8233855497a414b9d67bf22592c928a4 ]

When a function is annotated as "weak" and is overridden, the code is not
removed. If it is traced, the fentry/mcount location in the weak function
will be referenced by the "__mcount_loc" section. This will then be added
to the available_filter_functions list. Since only the address of the
functions are listed, to find the name to show, a search of kallsyms is
used.

Since kallsyms will return the function by simply finding the function
that the address is after but before the next function, an address of a
weak function will show up as the function before it. This is because
kallsyms does not save names of weak functions. This has caused issues in
the past, as now the traced weak function will be listed in
available_filter_functions with the name of the function before it.

At best, this will cause the previous function's name to be listed twice.
At worse, if the previous function was marked notrace, it will now show up
as a function that can be traced. Note that it only shows up that it can
be traced but will not be if enabled, which causes confusion.

 https://lore.kernel.org/all/20220412094923.0abe90955e5db486b7bca279@kernel.org/

The commit b39181f7c6907 ("ftrace: Add FTRACE_MCOUNT_MAX_OFFSET to avoid
adding weak function") was a workaround to this by checking the function
address before printing its name. If the address was too far from the
function given by the name then instead of printing the name it would
print: __ftrace_invalid_address___

The real issue is that these invalid addresses are listed in the ftrace
table look up which available_filter_functions is derived from. A place
holder must be listed in that file because set_ftrace_filter may take a
series of indexes into that file instead of names to be able to do O(1)
lookups to enable filtering (many tools use this method).

Even if kallsyms saved the size of the function, it does not remove the
need of having these place holders. The real solution is to not add a weak
function into the ftrace table in the first place.

To solve this, the sorttable.c code that sorts the mcount regions during
the build is modified to take a "nm -S vmlinux" input, sort it, and any
function listed in the mcount_loc section that is not within a boundary of
the function list given by nm is considered a weak function and is zeroed
out.

Note, this does not mean they will remain zero when booting as KASLR
will still shift those addresses. To handle this, the entries in the
mcount_loc section will be ignored if they are zero or match the
kaslr_offset() value.

Before:

 ~# grep __ftrace_invalid_address___ /sys/kernel/tracing/available_filter_functions | wc -l
 551

After:

 ~# grep __ftrace_invalid_address___ /sys/kernel/tracing/available_filter_functions | wc -l
 0

Cc: bpf 
Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Cc: Andrew Morton 
Cc: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Masahiro Yamada 
Cc: Nathan Chancellor 
Cc: Nicolas Schier 
Cc: Zheng Yejian 
Cc: Martin  Kelly 
Cc: Christophe Leroy 
Cc: Josh Poimboeuf 
Cc: Heiko Carstens 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Vasily Gorbik 
Cc: Alexander Gordeev 
Link: https://lore.kernel.org/20250218200022.883095980@goodmis.org
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Andrey Grodzovsky 
Signed-off-by: Greg Kroah-Hartman

kbuild: fix short log for AS in link-vmlinux.sh

2024-07-11T10:49:21+00:00

[ Upstream commit 3430f65d6130ccbc86f0ff45642eeb9e2032a600 ]

In convention, short logs print the output file, not the input file.

Let's change the suffix for 'AS' since it assembles *.S into *.o.

[Before]

  LD      .tmp_vmlinux.kallsyms1
  NM      .tmp_vmlinux.kallsyms1.syms
  KSYMS   .tmp_vmlinux.kallsyms1.S
  AS      .tmp_vmlinux.kallsyms1.S
  LD      .tmp_vmlinux.kallsyms2
  NM      .tmp_vmlinux.kallsyms2.syms
  KSYMS   .tmp_vmlinux.kallsyms2.S
  AS      .tmp_vmlinux.kallsyms2.S
  LD      vmlinux

[After]

  LD      .tmp_vmlinux.kallsyms1
  NM      .tmp_vmlinux.kallsyms1.syms
  KSYMS   .tmp_vmlinux.kallsyms1.S
  AS      .tmp_vmlinux.kallsyms1.o
  LD      .tmp_vmlinux.kallsyms2
  NM      .tmp_vmlinux.kallsyms2.syms
  KSYMS   .tmp_vmlinux.kallsyms2.S
  AS      .tmp_vmlinux.kallsyms2.o
  LD      vmlinux

Signed-off-by: Masahiro Yamada 
Signed-off-by: Sasha Levin

kbuild: Fix changing ELF file type for output of gen_btf for big endian

2024-02-23T08:25:02+00:00

commit e3a9ee963ad8ba677ca925149812c5932b49af69 upstream.

Commit 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF")
changed the ELF type of .btf.vmlinux.bin.o to ET_REL via dd, which works
fine for little endian platforms:

   00000000  7f 45 4c 46 02 01 01 00  00 00 00 00 00 00 00 00  |.ELF............|
  -00000010  03 00 b7 00 01 00 00 00  00 00 00 80 00 80 ff ff  |................|
  +00000010  01 00 b7 00 01 00 00 00  00 00 00 80 00 80 ff ff  |................|

However, for big endian platforms, it changes the wrong byte, resulting
in an invalid ELF file type, which ld.lld rejects:

   00000000  7f 45 4c 46 02 02 01 00  00 00 00 00 00 00 00 00  |.ELF............|
  -00000010  00 03 00 16 00 00 00 01  00 00 00 00 00 10 00 00  |................|
  +00000010  01 03 00 16 00 00 00 01  00 00 00 00 00 10 00 00  |................|

  Type:                              : 103

  ld.lld: error: .btf.vmlinux.bin.o: unknown file type

Fix this by updating the entire 16-bit e_type field rather than just a
single byte, so that everything works correctly for all platforms and
linkers.

   00000000  7f 45 4c 46 02 02 01 00  00 00 00 00 00 00 00 00  |.ELF............|
  -00000010  00 03 00 16 00 00 00 01  00 00 00 00 00 10 00 00  |................|
  +00000010  00 01 00 16 00 00 00 01  00 00 00 00 00 10 00 00  |................|

  Type:                              REL (Relocatable file)

While in the area, update the comment to mention that binutils 2.35+
matches LLD's behavior of rejecting an ET_EXEC input, which occurred
after the comment was added.

Cc: stable@vger.kernel.org
Fixes: 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF")
Link: https://github.com/llvm/llvm-project/pull/75643
Suggested-by: Masahiro Yamada 
Signed-off-by: Nathan Chancellor 
Reviewed-by: Fangrui Song 
Reviewed-by: Nicolas Schier 
Reviewed-by: Kees Cook 
Reviewed-by: Justin Stitt 
Signed-off-by: Masahiro Yamada 
Signed-off-by: Greg Kroah-Hartman

Merge tag 'kbuild-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2023-04-30T18:32:53+00:00

Pull Kbuild updates from Masahiro Yamada:

 - Refactor scripts/kallsyms to make it faster and easier to maintain

 - Clean up menuconfig

 - Provide Clang with hard-coded target triple instead of CROSS_COMPILE

 - Use -z pack-relative-relocs flags instead of --use-android-relr-tags
   for arm64 CONFIG_RELR

 - Add srcdeb-pkg target to build only a Debian source package

 - Add KDEB_SOURCE_COMPRESS option to specify the compression for a
   Debian source package

 - Misc cleanups and fixes

* tag 'kbuild-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: deb-pkg: specify targets in debian/rules as .PHONY
  sparc: unify sparc32/sparc64 archhelp
  kbuild: rpm-pkg: remove kernel-drm PROVIDES
  kbuild: deb-pkg: add KDEB_SOURCE_COMPRESS to specify source compression
  kbuild: add srcdeb-pkg target
  Makefile: use -z pack-relative-relocs
  kbuild: clang: do not use CROSS_COMPILE for target triple
  kconfig: menuconfig: reorder functions to remove forward declarations
  kconfig: menuconfig: remove unused M_EVENT macro
  kconfig: menuconfig: remove OLD_NCURSES macro
  kbuild: builddeb: Eliminate debian/arch use
  scripts/kallsyms: update the usage in the comment block
  scripts/kallsyms: decrease expand_symbol() / cleanup_symbol_name() calls
  scripts/kallsyms: change the output order
  scripts/kallsyms: move compiler-generated symbol patterns to mksysmap
  scripts/kallsyms: exclude symbols generated by itself dynamically
  scripts/mksysmap: use sed with in-line comments
  scripts/mksysmap: remove comments described in nm(1)
  scripts/kallsyms: remove redundant code for omitting U and N
  kallsyms: expand symbol name into comment for debugging

scripts/kallsyms: exclude symbols generated by itself dynamically

2023-04-17T02:03:56+00:00

Drop the symbols generated by scripts/kallsyms itself automatically
instead of maintaining the symbol list manually.

Pass the kallsyms object from the previous kallsyms step (if it exists)
as the third parameter of scripts/mksysmap, which will weed out the
generated symbols from the input to the next kallsyms step.

Signed-off-by: Masahiro Yamada

scripts/link-vmlinux.sh: fix error message presentation

2023-04-08T20:45:37+00:00

This comes out as

   Try make KALLSYMS_EXTRA_PASS=1 as a workaround

but we want quotes:

   Try "make KALLSYMS_EXTRA_PASS=1" as a workaround

Link: https://lkml.kernel.org/r/202303042034.Cjc7JTd0-lkp@intel.com
Cc: kernel test robot 
Signed-off-by: Andrew Morton

kallsyms: Correctly sequence symbols when CONFIG_LTO_CLANG=y

2022-11-13T02:47:36+00:00

LLVM appends various suffixes for local functions and variables, suffixes
observed:
 - foo.llvm.[0-9a-f]+
 - foo.[0-9a-f]+

Therefore, when CONFIG_LTO_CLANG=y, kallsyms_lookup_name() needs to
truncate the suffix of the symbol name before comparing the local function
or variable name.

Old implementation code:
-	if (strcmp(namebuf, name) == 0)
-		return kallsyms_sym_address(i);
-	if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
-		return kallsyms_sym_address(i);

The preceding process is traversed by address from low to high. That is,
for those with the same name after the suffix is removed, the one with
the smallest address is returned first. Therefore, when sorting in the
tool, if the raw names are the same, they should be sorted by address in
ascending order.

ASCII[.]   = 2e
ASCII[0-9] = 30,39
ASCII[A-Z] = 41,5a
ASCII[_]   = 5f
ASCII[a-z] = 61,7a

According to the preceding ASCII code values, the following sorting result
is strictly followed.
 ---------------------------------
|    main-key     |    sub-key    |
|---------------------------------|
|                 |  addr_lowest  |
|           |      ...      |
| . |      ...      |
|                 |  addr_highest |
|---------------------------------|
| ? |               |   //? is [_A-Za-z0-9]
 ---------------------------------

Signed-off-by: Zhen Lei 
Signed-off-by: Luis Chamberlain

kbuild: rebuild .vmlinux.export.o when its prerequisite is updated

2022-10-02T18:52:58+00:00

When include/linux/export-internal.h is updated, .vmlinux.export.o
must be rebuilt, but it does not happen because its rule is hidden
behind scripts/link-vmlinux.sh.

Move it out of the shell script, so that Make can see the dependency
between vmlinux and .vmlinux.export.o.

Move the vmlinux rule to scripts/Makefile.vmlinux.

Signed-off-by: Masahiro Yamada

kbuild: move modules.builtin(.modinfo) rules to Makefile.vmlinux_o

2022-10-02T18:52:58+00:00

Do not build modules.builtin(.modinfo) as a side-effect of vmlinux.

There are no good reason to rebuild them just because any of vmlinux's
prerequistes (vmlinux.lds, .vmlinux.export.c, etc.) has been updated.

Signed-off-by: Masahiro Yamada

kallsyms: take the input file instead of reading stdin

2022-10-02T09:06:05+00:00

This gets rid of the pipe operator connected with 'cat'.

Also use getopt_long() to parse the command line.

Signed-off-by: Masahiro Yamada