Commit 7b453719 ("kbuild: link symbol CRCs at final link, removing
CONFIG_MODULE_REL_CRCS") made modpost output CRCs in the same way
whether the EXPORT_SYMBOL() is placed in *.c or *.S.

For further cleanups, this commit applies a similar approach to the
entire data structure of EXPORT_SYMBOL().

The EXPORT_SYMBOL() compilation is split into two stages.

When a source file is compiled, EXPORT_SYMBOL() will be converted into
a dummy symbol in the .export_symbol section.

For example,

    EXPORT_SYMBOL(foo);
    EXPORT_SYMBOL_NS_GPL(bar, BAR_NAMESPACE);

will be encoded into the following assembly code:

    .section ".export_symbol","a"
    __export_symbol_foo:
            .asciz ""                      /* license */
            .asciz ""                      /* name space */
            .balign 8
            .quad foo                      /* symbol reference */
    .previous

    .section ".export_symbol","a"
    __export_symbol_bar:
            .asciz "GPL"                   /* license */
            .asciz "BAR_NAMESPACE"         /* name space */
            .balign 8
            .quad bar                      /* symbol reference */
    .previous

They are mere markers to tell modpost the name, license, and namespace
of the symbols. They will be dropped from the final vmlinux and modules
because the *(.export_symbol) will go into /DISCARD/ in the linker script.

Then, modpost extracts all the information about EXPORT_SYMBOL() from the
.export_symbol section, and generates the final C code:

    KSYMTAB_FUNC(foo, "", "");
    KSYMTAB_FUNC(bar, "_gpl", "BAR_NAMESPACE");

KSYMTAB_FUNC() (or KSYMTAB_DATA() if it is data) is expanded to struct
kernel_symbol that will be linked to the vmlinux or a module.

With this change, EXPORT_SYMBOL() works in the same way for *.c and *.S
files, providing the following benefits.

[1] Deprecate EXPORT_DATA_SYMBOL()

In the old days, EXPORT_SYMBOL() was only available in C files. To export
a symbol in *.S, EXPORT_SYMBOL() was placed in a separate *.c file.
arch/arm/kernel/armksyms.c is one example written in the classic manner.

Commit 22823ab4 ("EXPORT_SYMBOL() for asm") removed this limitation.
Since then, EXPORT_SYMBOL() can be placed close to the symbol definition
in *.S files. It was a nice improvement.

However, as that commit mentioned, you need to use EXPORT_DATA_SYMBOL()
for data objects on some architectures.

In the new approach, modpost checks symbol's type (STT_FUNC or not),
and outputs KSYMTAB_FUNC() or KSYMTAB_DATA() accordingly.

There are only two users of EXPORT_DATA_SYMBOL:

  EXPORT_DATA_SYMBOL_GPL(empty_zero_page)    (arch/ia64/kernel/head.S)
  EXPORT_DATA_SYMBOL(ia64_ivt)               (arch/ia64/kernel/ivt.S)

They are transformed as follows and output into .vmlinux.export.c

  KSYMTAB_DATA(empty_zero_page, "_gpl", "");
  KSYMTAB_DATA(ia64_ivt, "", "");

The other EXPORT_SYMBOL users in ia64 assembly are output as
KSYMTAB_FUNC().

EXPORT_DATA_SYMBOL() is now deprecated.

[2] merge <linux/export.h> and <asm-generic/export.h>

There are two similar header implementations:

  include/linux/export.h        for .c files
  include/asm-generic/export.h  for .S files

Ideally, the functionality should be consistent between them, but they
tend to diverge.

Commit 8651ec01 ("module: add support for symbol namespaces.") did
not support the namespace for *.S files.

This commit shifts the essential implementation part to C, which supports
EXPORT_SYMBOL_NS() for *.S files.

<asm/export.h> and <asm-generic/export.h> will remain as a wrapper of
<linux/export.h> for a while.

They will be removed after #include <asm/export.h> directives are all
replaced with #include <linux/export.h>.

[3] Implement CONFIG_TRIM_UNUSED_KSYMS in one-pass algorithm (by a later commit)

When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses
the directory tree to determine which EXPORT_SYMBOL to trim. If an
EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the
second traverse, where some source files are recompiled with their
EXPORT_SYMBOL() tuned into a no-op.

We can do this better now; modpost can selectively emit KSYMTAB entries
that are really used by modules.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

The next commit will use it.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

ASM_NL is useful not only in *.S files but also in .c files for using
inline assembler in C code.

On ARC, however, ASM_NL is evaluated inconsistently. It is expanded to
a backquote (`) in *.S files, but a semicolon (;) in *.c files because
arch/arc/include/asm/linkage.h defines it inside #ifdef __ASSEMBLY__,
so the definition for C code falls back to the default value defined in
include/linux/linkage.h.

If ASM_NL is used in inline assembler in .c files, it will result in
wrong assembly code because a semicolon is not an instruction separator,
but the start of a comment for ARC.

Move ASM_NL (also __ALIGN and __ALIGN_STR) out of the #ifdef.

Fixes: 9df62f05 ("arch: use ASM_NL instead of ';' for assembler new line character in the macro")
Fixes: 8d92e992 ("ARC: define __ALIGN_STR and __ALIGN symbols for ARC")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

You do not need to decide the buffer size statically.

Use getline() to grow the line buffer as needed.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

getopt_long() does not modify this.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

This reverts commit cead61a6.

It exported __stack_smash_handler and __guard, while they may not be
defined by anyone.

The code *declares* __stack_smash_handler and __guard. It does not
create weak symbols. If no external library is linked, they are left
undefined, but yet exported.

If a loadable module tries to access non-existing symbols, bad things
(a page fault, NULL pointer dereference, etc.) will happen. So, the
current code is wrong and dangerous.

If the code were written as follows, it would *define* them as weak
symbols so modules would be able to get access to them.

  void (*__stack_smash_handler)(void *) __attribute__((weak));
  EXPORT_SYMBOL(__stack_smash_handler);

  long __guard __attribute__((weak));
  EXPORT_SYMBOL(__guard);

In fact, modpost forbids exporting undefined symbols. It shows an error
message if it detects such a mistake.

  ERROR: modpost: "..." [...] was exported without definition

Unfortunately, it is checked only when the code is built as modular.
The problem described above has been unnoticed for a long time because
arch/um/os-Linux/user_syms.c is always built-in.

With a planned change in Kbuild, exporting undefined symbols will always
result in a build error instead of a run-time error. It is a good thing,
but we need to fix the breakage in advance.

One fix is to define weak symbols as shown above. An alternative is to
export them conditionally as follows:

  #ifdef CONFIG_STACKPROTECTOR
  extern void __stack_smash_handler(void *);
  EXPORT_SYMBOL(__stack_smash_handler);

  external long __guard;
  EXPORT_SYMBOL(__guard);
  #endif

This is what other architectures do; EXPORT_SYMBOL(__stack_chk_guard)
is guarded by #ifdef CONFIG_STACKPROTECTOR.

However, adding the #ifdef guard is not sensible because UML cannot
enable the stack-protector in the first place! (Please note UML does
not select HAVE_STACKPROTECTOR in Kconfig.)

So, the code is already broken (and unused) in multiple ways.

Just remove.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

For W=2, we can enable more kernel-doc warnings,
such as missing return value descriptions etc.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The kernel-doc script currently reports a number of issues
only in "verbose" mode, but that's initialized from V=1
(via KBUILD_VERBOSE), so if you use KDOC_WERROR=1 then
adding V=1 might actually break the build. This is rather
unexpected.

Change kernel-doc to not change its behaviour wrt. errors
(or warnings) when verbose mode is enabled, but rather add
separate warning flags (and -Wall) for it. Allow enabling
those flags via environment/make variables in the kernel's
build system for easier user use, but to not have to parse
them in the script itself.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The > comparison should be >= to prevent an out of bounds array
access.

Fixes: 52dc0595 ("modpost: handle relocations mismatch in __ex_table.")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

streamline_config.pl currently searches for CONFIG options in Kconfig
files as $(CONFIG_FOO). But some Kconfigs (e.g. thunderbolt) use
${CONFIG_FOO}. So fix up the regex to accept both.

This fixes:
$ make LSMOD=`pwd/`/lsmod localmodconfig
using config: '.config'
thunderbolt config not found!!
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

After commit feb843a4 ("kbuild: add $(CLANG_FLAGS) to
KBUILD_CPPFLAGS"), there is an error while building certain PowerPC
assembly files with clang:

  arch/powerpc/lib/copypage_power7.S: Assembler messages:
  arch/powerpc/lib/copypage_power7.S:34: Error: junk at end of line: `0b01000'
  arch/powerpc/lib/copypage_power7.S:35: Error: junk at end of line: `0b01010'
  arch/powerpc/lib/copypage_power7.S:37: Error: junk at end of line: `0b01000'
  arch/powerpc/lib/copypage_power7.S:38: Error: junk at end of line: `0b01010'
  arch/powerpc/lib/copypage_power7.S:40: Error: junk at end of line: `0b01010'
  clang: error: assembler command failed with exit code 1 (use -v to see invocation)

as-option only uses KBUILD_AFLAGS, so after removing CLANG_FLAGS from
KBUILD_AFLAGS, there is no more '--target=' or '--prefix=' flags. As a
result of those missing flags, the host target
will be tested during as-option calls and likely fail, meaning necessary
flags may not get added when building assembly files, resulting in
errors like seen above.

Add KBUILD_CPPFLAGS to as-option invocations to clear up the errors.
This should have been done in commit d5c8d6e0 ("kbuild: Update
assembler calls to use proper flags and language target"), which
switched from using the assembler target to the assembler-with-cpp
target, so flags that affect preprocessing are passed along in all
relevant tests. as-option now mirrors cc-option.

Fixes: feb843a4 ("kbuild: add $(CLANG_FLAGS) to KBUILD_CPPFLAGS")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/CA+G9fYs=koW9WardsTtora+nMgLR3raHz-LSLr58tgX4T5Mxag@mail.gmail.com/Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Similarly to "__kvm_nvhe_", filter out any local symbol that was
prefixed with "__pi_" (generated when CONFIG_RANDOMIZE_BASE=y) when
compiling System.map and in kallsyms.
Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The backslash characters escaping '$' in the command to sed (intended to
prevent it from interpreting '$' as "end-of-line") are currently being
consumed by the Shell (where they mean that sh should not evaluate what
follows '$' as a variable name). This means that

    sed -e "/ \$/d"

executes the script

    / $/d

instead of the intended

    / \$/d

So escape twice in mksysmap any '$' that actually needs to reach sed
escaped so that the backslash survives the Shell.

Fixes: c4802044 ("scripts/mksysmap: use sed with in-line comments")
Fixes: 320e7c9d ("scripts/kallsyms: move compiler-generated symbol patterns to mksysmap")
Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

"No build warning" is a strong requirement these days, so you must fix
all issues before enabling a new warning flag.

We often add a new warning to W=1 first so that the kbuild test robot
blocks new breakages.

This commit allows modpost to show extra warnings only when W=1
(or KBUILD_EXTRA_WARN=1) is given.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

gen_initramfs.sh has an internal dependency on KBUILD_BUILD_TIMESTAMP
for generating file mtimes that is not exposed to make, so changing
KBUILD_BUILD_TIMESTAMP will not trigger a rebuild of the archive.

Declare the mtime date as a new parameter to gen_initramfs.sh to encode
KBUILD_BUILD_TIMESTAMP in the shell command, thereby making make aware
of the dependency.

It will rebuild if KBUILD_BUILD_TIMESTAMP changes or is newly set/unset.
It will _not_ rebuild if KBUILD_BUILD_TIMESTAMP is unset before and
after. This should be fine for anyone who doesn't care about setting
specific build times in the first place.
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Tested-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

When preprocessing arch/*/kernel/vmlinux.lds.S, the target triple is
not passed to $(CPP) because we add it only to KBUILD_{C,A}FLAGS.

As a result, the linker script is preprocessed with predefined macros
for the build host instead of the target.

Assuming you use an x86 build machine, compare the following:

 $ clang -dM -E -x c /dev/null
 $ clang -dM -E -x c /dev/null -target aarch64-linux-gnu

There is no actual problem presumably because our linker scripts do not
rely on such predefined macros, but it is better to define correct ones.

Move $(CLANG_FLAGS) to KBUILD_CPPFLAGS, so that all *.c, *.S, *.lds.S
will be processed with the proper target triple.

[Note]
After the patch submission, we got an actual problem that needs this
commit. (CBL issue 1859)

Link: https://github.com/ClangBuiltLinux/linux/issues/1859Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>

A future change will move CLANG_FLAGS from KBUILD_{A,C}FLAGS to
KBUILD_CPPFLAGS so that '--target' is available while preprocessing.
When that occurs, the following errors appear multiple times when
building ARCH=powerpc powernv_defconfig:

  ld.lld: error: vmlinux.a(arch/powerpc/kernel/head_64.o):(.text+0x12d4): relocation R_PPC64_ADDR16_HI out of range: -4611686018409717520 is not in [-2147483648, 2147483647]; references '__start___soft_mask_table'
  ld.lld: error: vmlinux.a(arch/powerpc/kernel/head_64.o):(.text+0x12e8): relocation R_PPC64_ADDR16_HI out of range: -4611686018409717392 is not in [-2147483648, 2147483647]; references '__stop___soft_mask_table'

Diffing the .o.cmd files reveals that -DHAVE_AS_ATHIGH=1 is not present
anymore, because as-instr only uses KBUILD_AFLAGS, which will no longer
contain '--target'.

Mirror Kconfig's as-instr and add CLANG_FLAGS explicitly to the
invocation to ensure the target information is always present.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

A future change will move CLANG_FLAGS from KBUILD_{A,C}FLAGS to
KBUILD_CPPFLAGS so that '--target' is available while preprocessing.
When that occurs, the following error appears when building the compat
PowerPC vDSO:

  clang: error: unsupported option '-mbig-endian' for target 'x86_64-pc-linux-gnu'
  make[3]: *** [.../arch/powerpc/kernel/vdso/Makefile:76: arch/powerpc/kernel/vdso/vdso32.so.dbg] Error 1

Explicitly add CLANG_FLAGS to ldflags-y, so that '--target' will always
be present.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

A future change will move CLANG_FLAGS from KBUILD_{A,C}FLAGS to
KBUILD_CPPFLAGS so that '--target' is available while preprocessing.
When that occurs, the following error appears when building ARCH=mips
with clang (tip of tree error shown):

  clang: error: unsupported option '-mabi=' for target 'x86_64-pc-linux-gnu'

Add KBUILD_CPPFLAGS in the CHECKFLAGS invocation to keep everything
working after the move.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

For ARM, modpost fails to detect some types of section mismatches.

  [test code]

    .section .init.data,"aw"
    bar:
            .long 0

    .section .data,"aw"
    .globl foo
    foo:
            .long bar - .

It is apparently a bad reference, but modpost does not report anything.

The test code above produces the following relocations.

  Relocation section '.rel.data' at offset 0xe8 contains 1 entry:
   Offset     Info    Type            Sym.Value  Sym. Name
  00000000  00000403 R_ARM_REL32       00000000   .init.data

Currently, R_ARM_REL32 is just skipped.

Handle it like R_ARM_ABS32.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

addend_arm_rel() processes R_ARM_THM_CALL, R_ARM_THM_JUMP24,
R_ARM_THM_JUMP19 in a wrong way.

Here, test code.

[test code for R_ARM_THM_JUMP24]

  .section .init.text,"ax"
  bar:
          bx      lr

  .section .text,"ax"
  .globl foo
  foo:
          b       bar

[test code for R_ARM_THM_CALL]

  .section .init.text,"ax"
  bar:
          bx      lr

  .section .text,"ax"
  .globl foo
  foo:
          push    {lr}
          bl      bar
          pop     {pc}

If you compile it with CONFIG_THUMB2_KERNEL=y, modpost will show the
symbol name, (unknown).

  WARNING: modpost: vmlinux.o: section mismatch in reference: foo (section: .text) -> (unknown) (section: .init.text)

(You need to use GNU linker instead of LLD to reproduce it.)

Fix the code to make modpost show the correct symbol name. I checked
arch/arm/kernel/module.c to learn the encoding of R_ARM_THM_CALL and
R_ARM_THM_JUMP24. The module does not support R_ARM_THM_JUMP19, but
I checked its encoding in ARM ARM.

The '+4' is the compensation for pc-relative instruction. It is
documented in "ELF for the Arm Architecture" [1].

  "If the relocation is pc-relative then compensation for the PC bias
  (the PC value is 8 bytes ahead of the executing instruction in Arm
  state and 4 bytes in Thumb state) must be encoded in the relocation
  by the object producer."

[1]: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst

Fixes: c9698e5c ("ARM: 7964/1: Detect section mismatches in thumb relocations")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

When CONFIG_THUMB2_KERNEL is enabled, modpost fails to detect some
types of section mismatches.

  [test code]

    #include <linux/init.h>

    int __initdata foo;
    int get_foo(void) { return foo; }

It is apparently a bad reference, but modpost does not report anything.

The test code above produces the following relocations.

  Relocation section '.rel.text' at offset 0x1e8 contains 2 entries:
   Offset     Info    Type            Sym.Value  Sym. Name
  00000000  0000052f R_ARM_THM_MOVW_AB 00000000   .LANCHOR0
  00000004  00000530 R_ARM_THM_MOVT_AB 00000000   .LANCHOR0

Currently, R_ARM_THM_MOVW_ABS_NC and R_ARM_THM_MOVT_ABS are just skipped.

Add code to handle them. I checked arch/arm/kernel/module.c to learn
how the offset is encoded in the instruction.

One more thing to note for Thumb instructions - the st_value is an odd
value, so you need to mask the bit 0 to get the offset. Otherwise, you
will get an off-by-one error in the nearest symbol look-up.

It is documented in "ELF for the ARM Architecture" [1]:

  In addition to the normal rules for symbol values the following rules
  shall also apply to symbols of type STT_FUNC:

   * If the symbol addresses an Arm instruction, its value is the
     address of the instruction (in a relocatable object, the offset
     of the instruction from the start of the section containing it).

   * If the symbol addresses a Thumb instruction, its value is the
     address of the instruction with bit zero set (in a relocatable
     object, the section offset with bit zero set).

   * For the purposes of relocation the value used shall be the address
     of the instruction (st_value & ~1).

[1]: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rstSigned-off-by: Masahiro Yamada <masahiroy@kernel.org>

find_fromsym() and find_tosym() are similar - both of them iterate
in the .symtab section and return the nearest symbol.

The difference between them is that find_tosym() allows a negative
distance, but the distance must be less than 20.

Factor out the common part into find_nearest_sym().
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

For ARM defconfig (i.e. multi_v7_defconfig), modpost fails to detect
some types of section mismatches.

  [test code]

    #include <linux/init.h>

    int __initdata foo;
    int get_foo(void) { return foo; }

It is apparently a bad reference, but modpost does not report anything.

The test code above produces the following relocations.

  Relocation section '.rel.text' at offset 0x200 contains 2 entries:
   Offset     Info    Type            Sym.Value  Sym. Name
  00000000  0000062b R_ARM_MOVW_ABS_NC 00000000   .LANCHOR0
  00000004  0000062c R_ARM_MOVT_ABS    00000000   .LANCHOR0

Currently, R_ARM_MOVW_ABS_NC and R_ARM_MOVT_ABS are just skipped.

Add code to handle them. I checked arch/arm/kernel/module.c to learn
how the offset is encoded in the instruction.

The referenced symbol in relocation might be a local anchor.
If is_valid_name() returns false, let's search for a better symbol name.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

addend_arm_rel() processes R_ARM_PC24, R_ARM_CALL, R_ARM_JUMP24 in a
wrong way.

Here, test code.

[test code for R_ARM_JUMP24]

  .section .init.text,"ax"
  bar:
          bx      lr

  .section .text,"ax"
  .globl foo
  foo:
          b       bar

[test code for R_ARM_CALL]

  .section .init.text,"ax"
  bar:
          bx      lr

  .section .text,"ax"
  .globl foo
  foo:
          push    {lr}
          bl      bar
          pop     {pc}

If you compile it with ARM multi_v7_defconfig, modpost will show the
symbol name, (unknown).

  WARNING: modpost: vmlinux.o: section mismatch in reference: foo (section: .text) -> (unknown) (section: .init.text)

(You need to use GNU linker instead of LLD to reproduce it.)

Fix the code to make modpost show the correct symbol name.

I imported (with adjustment) sign_extend32() from include/linux/bitops.h.

The '+8' is the compensation for pc-relative instruction. It is
documented in "ELF for the Arm Architecture" [1].

  "If the relocation is pc-relative then compensation for the PC bias
  (the PC value is 8 bytes ahead of the executing instruction in Arm
  state and 4 bytes in Thumb state) must be encoded in the relocation
  by the object producer."

[1]: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst

Fixes: 56a974fa ("kbuild: make better section mismatch reports on arm")
Fixes: 6e2e340b ("ARM: 7324/1: modpost: Fix section warnings for ARM for many compilers")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

addend_arm_rel() processes R_ARM_ABS32 in a wrong way.

Here, test code.

  [test code 1]

    #include <linux/init.h>

    int __initdata foo;
    int get_foo(void) { return foo; }

If you compile it with ARM versatile_defconfig, modpost will show the
symbol name, (unknown).

  WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> (unknown) (section: .init.data)

(You need to use GNU linker instead of LLD to reproduce it.)

If you compile it for other architectures, modpost will show the correct
symbol name.

  WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data)

For R_ARM_ABS32, addend_arm_rel() sets r->r_addend to a wrong value.

I just mimicked the code in arch/arm/kernel/module.c.

However, there is more difficulty for ARM.

Here, test code.

  [test code 2]

    #include <linux/init.h>

    int __initdata foo;
    int get_foo(void) { return foo; }

    int __initdata bar;
    int get_bar(void) { return bar; }

With this commit applied, modpost will show the following messages
for ARM versatile_defconfig:

  WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data)
  WARNING: modpost: vmlinux.o: section mismatch in reference: get_bar (section: .text) -> foo (section: .init.data)

The reference from 'get_bar' to 'foo' seems wrong.

I have no solution for this because it is true in assembly level.

In the following output, relocation at 0x1c is no longer associated
with 'bar'. The two relocation entries point to the same symbol, and
the offset to 'bar' is encoded in the instruction 'r0, [r3, #4]'.

  Disassembly of section .text:

  00000000 <get_foo>:
     0: e59f3004          ldr     r3, [pc, #4]   @ c <get_foo+0xc>
     4: e5930000          ldr     r0, [r3]
     8: e12fff1e          bx      lr
     c: 00000000          .word   0x00000000

  00000010 <get_bar>:
    10: e59f3004          ldr     r3, [pc, #4]   @ 1c <get_bar+0xc>
    14: e5930004          ldr     r0, [r3, #4]
    18: e12fff1e          bx      lr
    1c: 00000000          .word   0x00000000

  Relocation section '.rel.text' at offset 0x244 contains 2 entries:
   Offset     Info    Type            Sym.Value  Sym. Name
  0000000c  00000c02 R_ARM_ABS32       00000000   .init.data
  0000001c  00000c02 R_ARM_ABS32       00000000   .init.data

When find_elf_symbol() gets into a situation where relsym->st_name is
zero, there is no guarantee to get the symbol name as written in C.

I am keeping the current logic because it is useful in many architectures,
but the symbol name is not always correct depending on the optimization.
I left some comments in find_tosym().

Fixes: 56a974fa ("kbuild: make better section mismatch reports on arm")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Use PATTERNS() macros to remove unneeded array definitions.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

There is no distinction between TEXT_TO_ANY_EXIT and DATA_TO_ANY_EXIT.
Just merge them.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

You can merge these entries.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

This check is unneeded. Without it, sec_name() will returns the null
string "", then section_mismatch() will return immediately.

Anyway, special section indices rarely appear in these loops.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

r_offset/r_addend holds the offset address from/to which a symbol is
referenced. It is unclear unless you are familiar with ELF.

Rename them to faddr, taddr, respectively. The prefix 'f' means 'from',
't' means 'to'.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

find_tosym() takes 'sym' and stores the return value to another
variable 'to'. You can use the same variable because we want to
replace the original one when appropriate.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

secref_whitelist() does not use the argument 'mismatch'.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

This reverts commit a4d26f1a.

The variable 'fromsym' never starts with ".L" since commit 87e5b1e8
("module: Sync code of is_arm_mapping_symbol()").

In other words, Pattern 6 is now dead code.

Previously, the .LANCHOR1 hid the symbols listed in Pattern 2.

87e5b1e8 provided a better solution.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

tar is used to build the kernel with CONFIG_IKHEADERS.

GNU tar 1.28 or later is required.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

This reverts commit 700dea5a.

The reason for that commit was --sort=ORDER introduced in
tar 1.28 (2014). More than 3 years have passed since then.

Requiring GNU tar 1.28 should be fine now because we require
GCC 5.1 (2015).
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

Kernel build now uses the gtags "-C (--directory)" option, available
since GNU GLOBAL v6.6.5.  Update the documentation accordingly.
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Cc: <stable@vger.kernel.org>
Link: https://lists.gnu.org/archive/html/info-global/2020-09/msg00000.htmlSigned-off-by: Masahiro Yamada <masahiroy@kernel.org>

gtags considers any file outside of its current working directory
"outside the source tree" and refuses to index it. For O= kernel builds,
or when "make" is invoked from a directory other then the kernel source
tree, gtags ignores the entire kernel source and generates an empty
index.

Force-set gtags current working directory to the kernel source tree.

Due to commit 9da0763b ("kbuild: Use relative path when building in
a subdir of the source tree"), if the kernel build is done in a
sub-directory of the kernel source tree, the kernel Makefile will set
the kernel's $srctree to ".." for shorter compile-time and run-time
warnings. Consequently, the list of files to be indexed will be in the
"../*" form, rendering all such paths invalid once gtags switches to the
kernel source tree as its current working directory.

If gtags indexing is requested and the build directory is not the kernel
source tree, index all files in absolute-path form.

Note, indexing in absolute-path form will not affect the generated
index, as paths in gtags indices are always relative to the gtags "root
directory" anyway (as evidenced by "gtags --dump").
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

find_elf_symbol() and find_elf_symbol2() are not good names.

Rename them to find_tosym(), find_fromsym(), respectively.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

find_elf_symbol2() converts the section index to the section name,
then compares the two strings in each iteration. This is slow.

It is faster to compare the section indices (i.e. integers) directly.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>