linux-toradex.git/include/linux/compiler.h, branch v6.6-rc5

tracing: make ftrace_likely_update() declaration visible

2023-05-17T16:36:46+00:00

This function is only used when CONFIG_TRACE_BRANCH_PROFILING is set and
DISABLE_BRANCH_PROFILING is not set, and the declaration is hidden
behind this combination of tests.

But that causes a warning when building with CONFIG_TRACING_BRANCHES,
since that sets DISABLE_BRANCH_PROFILING for the tracing code, and the
declaration is thus hidden:

  kernel/trace/trace_branch.c:205:6: error: no previous prototype for 'ftrace_likely_update' [-Werror=missing-prototypes]

Move the declaration out of the #ifdef to avoid the warning.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Linus Torvalds

overflow: Introduce overflows_type() and castable_to_type()

2022-11-02T19:39:27+00:00

Implement a robust overflows_type() macro to test if a variable or
constant value would overflow another variable or type. This can be
used as a constant expression for static_assert() (which requires a
constant expression[1][2]) when used on constant values. This must be
constructed manually, since __builtin_add_overflow() does not produce
a constant expression[3].

Additionally adds castable_to_type(), similar to __same_type(), but for
checking if a constant value would overflow if cast to a given type.

Add unit tests for overflows_type(), __same_type(), and castable_to_type()
to the existing KUnit "overflow" test:

[16:03:33] ================== overflow (21 subtests) ==================
...
[16:03:33] [PASSED] overflows_type_test
[16:03:33] [PASSED] same_type_test
[16:03:33] [PASSED] castable_to_type_test
[16:03:33] ==================== [PASSED] overflow =====================
[16:03:33] ============================================================
[16:03:33] Testing complete. Ran 21 tests: passed: 21
[16:03:33] Elapsed time: 24.022s total, 0.002s configuring, 22.598s building, 0.767s running

[1] https://en.cppreference.com/w/c/language/_Static_assert
[2] C11 standard (ISO/IEC 9899:2011): 6.7.10 Static assertions
[3] https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html
    6.56 Built-in Functions to Perform Arithmetic with Overflow Checking
    Built-in Function: bool __builtin_add_overflow (type1 a, type2 b,

Cc: Luc Van Oostenryck 
Cc: Nathan Chancellor 
Cc: Nick Desaulniers 
Cc: Tom Rix 
Cc: Daniel Latypov 
Cc: Vitor Massaru Iha 
Cc: "Gustavo A. R. Silva" 
Cc: Jani Nikula 
Cc: Mauro Carvalho Chehab 
Cc: linux-hardening@vger.kernel.org
Cc: llvm@lists.linux.dev
Co-developed-by: Gwan-gyeong Mun 
Signed-off-by: Gwan-gyeong Mun 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20221024201125.1416422-1-gwan-gyeong.mun@intel.com

treewide: Drop function_nocfi

2022-09-26T17:13:14+00:00

With -fsanitize=kcfi, we no longer need function_nocfi() as
the compiler won't change function references to point to a
jump table. Remove all implementations and uses of the macro.

Signed-off-by: Sami Tolvanen 
Reviewed-by: Kees Cook 
Tested-by: Kees Cook 
Tested-by: Nathan Chancellor 
Acked-by: Peter Zijlstra (Intel) 
Tested-by: Peter Zijlstra (Intel) 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20220908215504.3686827-14-samitolvanen@google.com

cfi: Drop __CFI_ADDRESSABLE

2022-09-26T17:13:13+00:00

The __CFI_ADDRESSABLE macro is used for init_module and cleanup_module
to ensure we have the address of the CFI jump table, and with
CONFIG_X86_KERNEL_IBT to ensure LTO won't optimize away the symbols.
As __CFI_ADDRESSABLE is no longer necessary with -fsanitize=kcfi, add
a more flexible version of the __ADDRESSABLE macro and always ensure
these symbols won't be dropped.

Signed-off-by: Sami Tolvanen 
Reviewed-by: Kees Cook 
Tested-by: Kees Cook 
Tested-by: Nathan Chancellor 
Acked-by: Peter Zijlstra (Intel) 
Tested-by: Peter Zijlstra (Intel) 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20220908215504.3686827-5-samitolvanen@google.com

tracing: Define the is_signed_type() macro once

2022-08-29T20:29:40+00:00

There are two definitions of the is_signed_type() macro: one in
 and a second definition in .

As suggested by Linus, move the definition of the is_signed_type() macro
into the  header file.  Change the definition of the
is_signed_type() macro to make sure that it does not trigger any sparse
warnings with future versions of sparse for bitwise types.

Link: https://lore.kernel.org/all/CAHk-=whjH6p+qzwUdx5SOVVHjS3WvzJQr6mDUwhEyTf6pJWzaQ@mail.gmail.com/
Link: https://lore.kernel.org/all/CAHk-=wjQGnVfb4jehFR0XyZikdQvCZouE96xR_nnf5kqaM5qqQ@mail.gmail.com/
Cc: Rasmus Villemoes 
Cc: Steven Rostedt 
Acked-by: Kees Cook 
Signed-off-by: Bart Van Assche 
Signed-off-by: Linus Torvalds

objtool: Add CONFIG_OBJTOOL

2022-04-22T10:32:03+00:00

Now that stack validation is an optional feature of objtool, add
CONFIG_OBJTOOL and replace most usages of CONFIG_STACK_VALIDATION with
it.

CONFIG_STACK_VALIDATION can now be considered to be frame-pointer
specific.  CONFIG_UNWINDER_ORC is already inherently valid for live
patching, so no need to "validate" it.

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Miroslav Benes 
Link: https://lkml.kernel.org/r/939bf3d85604b2a126412bf11af6e3bd3b872bcb.1650300597.git.jpoimboe@redhat.com

x86,objtool: Move the ASM_REACHABLE annotation to objtool.h

2022-03-15T09:32:45+00:00

Because we need a variant for .S files too.

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/Yi9gOW9f1GGwwUD6@hirez.programming.kicks-ass.net

x86/bug: Merge annotate_reachable() into _BUG_FLAGS() asm

2022-02-02T22:41:04+00:00

In __WARN_FLAGS(), we had two asm statements (abbreviated):

  asm volatile("ud2");
  asm volatile(".pushsection .discard.reachable");

These pair of statements are used to trigger an exception, but then help
objtool understand that for warnings, control flow will be restored
immediately afterwards.

The problem is that volatile is not a compiler barrier. GCC explicitly
documents this:

> Note that the compiler can move even volatile asm instructions
> relative to other code, including across jump instructions.

Also, no clobbers are specified to prevent instructions from subsequent
statements from being scheduled by compiler before the second asm
statement. This can lead to instructions from subsequent statements
being emitted by the compiler before the second asm statement.

Providing a scheduling model such as via -march= options enables the
compiler to better schedule instructions with known latencies to hide
latencies from data hazards compared to inline asm statements in which
latencies are not estimated.

If an instruction gets scheduled by the compiler between the two asm
statements, then objtool will think that it is not reachable, producing
a warning.

To prevent instructions from being scheduled in between the two asm
statements, merge them.

Also remove an unnecessary unreachable() asm annotation from BUG() in
favor of __builtin_unreachable(). objtool is able to track that the ud2
from BUG() terminates control flow within the function.

Link: https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Volatile
Link: https://github.com/ClangBuiltLinux/linux/issues/1483
Signed-off-by: Nick Desaulniers 
Signed-off-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20220202205557.2260694-1-ndesaulniers@google.com

compiler.h: Fix annotation macro misplacement with Clang

2021-12-21T23:09:46+00:00

When building with Clang and CONFIG_TRACE_BRANCH_PROFILING, there are a
lot of unreachable warnings, like:

  arch/x86/kernel/traps.o: warning: objtool: handle_xfd_event()+0x134: unreachable instruction

Without an input to the inline asm, 'volatile' is ignored for some
reason and Clang feels free to move the reachable() annotation away from
its intended location.

Fix that by re-adding the counter value to the inputs.

Fixes: f1069a8756b9 ("compiler.h: Avoid using inline asm operand modifiers")
Fixes: c199f64ff93c ("instrumentation.h: Avoid using inline asm operand modifiers")
Reported-by: kernel test robot 
Signed-off-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/0417e96909b97a406323409210de7bf13df0b170.1636410380.git.jpoimboe@redhat.com
Cc: Peter Zijlstra 
Cc: x86@kernel.org
Cc: Vasily Gorbik 
Cc: Miroslav Benes

compiler.h: Introduce absolute_pointer macro

2021-09-15T19:04:28+00:00

absolute_pointer() disassociates a pointer from its originating symbol
type and context. Use it to prevent compiler warnings/errors such as

  drivers/net/ethernet/i825xx/82596.c: In function 'i82596_probe':
  arch/m68k/include/asm/string.h:72:25: error:
	'__builtin_memcpy' reading 6 bytes from a region of size 0 [-Werror=stringop-overread]

Such warnings may be reported by gcc 11.x for string and memory
operations on fixed addresses.

Suggested-by: Linus Torvalds 
Signed-off-by: Guenter Roeck 
Reviewed-by: Geert Uytterhoeven 
Signed-off-by: Linus Torvalds