kernel/linux.git/include/linux/compiler.h, branch v5.10.257

minmax: improve macro expansion and type checking

2025-10-29T13:01:16+00:00

[ Upstream commit 22f5468731491e53356ba7c028f0fdea20b18e2c ] This clarifies the rules for min()/max()/clamp() type checking and makes them a much more efficient macro expansion. In particular, we now look at the type and range of the inputs to see whether they work together, generating a mask of acceptable comparisons, and then just verifying that the inputs have a shared case: - an expression with a signed type can be used for (1) signed comparisons (2) unsigned comparisons if it is statically known to have a non-negative value - an expression with an unsigned type can be used for (3) unsigned comparison (4) signed comparisons if the type is smaller than 'int' and thus the C integer promotion rules will make it signed anyway Here rule (1) and (3) are obvious, and rule (2) is important in order to allow obvious trivial constants to be used together with unsigned values. Rule (4) is not necessarily a good idea, but matches what we used to do, and we have extant cases of this situation in the kernel. Notably with bcachefs having an expression like min(bch2_bucket_sectors_dirty(a), ca->mi.bucket_size) where bch2_bucket_sectors_dirty() returns an 's64', and 'ca->mi.bucket_size' is of type 'u16'. Technically that bcachefs comparison is clearly sensible on a C type level, because the 'u16' will go through the normal C integer promotion, and become 'int', and then we're comparing two signed values and everything looks sane. However, it's not entirely clear that a 'min(s64,u16)' operation makes a lot of conceptual sense, and it's possible that we will remove rule (4). After all, the _reason_ we have these complicated type checks is exactly that the C type promotion rules are not very intuitive. But at least for now the rule is in place for backwards compatibility. Also note that rule (2) existed before, but is hugely relaxed by this commit. It used to be true only for the simplest compile-time non-negative integer constants. The new macro model will allow cases where the compiler can trivially see that an expression is non-negative even if it isn't necessarily a constant. For example, the amdgpu driver does min_t(size_t, sizeof(fru_info->serial), pia[addr] & 0x3F)); because our old 'min()' macro would see that 'pia[addr] & 0x3F' is of type 'int' and clearly not a C constant expression, so doing a 'min()' with a 'size_t' is a signedness violation. Our new 'min()' macro still sees that 'pia[addr] & 0x3F' is of type 'int', but is smart enough to also see that it is clearly non-negative, and thus would allow that case without any complaints. Cc: Arnd Bergmann Cc: David Laight Cc: Lorenzo Stoakes Signed-off-by: Linus Torvalds Signed-off-by: Eliav Farber Signed-off-by: Greg Kroah-Hartman

overflow, tracing: Define the is_signed_type() macro once

2025-10-29T13:01:15+00:00

[ Upstream commit 92d23c6e94157739b997cacce151586a0d07bb8a ] There are two definitions of the is_signed_type() macro: one in and a second definition in . As suggested by Linus Torvalds, 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. See also: https://lore.kernel.org/all/CAHk-=whjH6p+qzwUdx5SOVVHjS3WvzJQr6mDUwhEyTf6pJWzaQ@mail.gmail.com/ https://lore.kernel.org/all/CAHk-=wjQGnVfb4jehFR0XyZikdQvCZouE96xR_nnf5kqaM5qqQ@mail.gmail.com/ Cc: Andrew Morton Cc: Arnd Bergmann Cc: Dan Williams Cc: Eric Dumazet Cc: Ingo Molnar Cc: Isabella Basso Cc: "Jason A. Donenfeld" Cc: Josh Poimboeuf Cc: Luc Van Oostenryck Cc: Masami Hiramatsu Cc: Nathan Chancellor Cc: Peter Zijlstra Cc: Rasmus Villemoes Cc: Sander Vanheule Cc: Steven Rostedt Cc: Vlastimil Babka Cc: Yury Norov Signed-off-by: Bart Van Assche Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220826162116.1050972-3-bvanassche@acm.org Signed-off-by: Eliav Farber Signed-off-by: Greg Kroah-Hartman

compiler: remove __ADDRESSABLE_ASM{_STR,}() again

2025-08-28T14:22:58+00:00

[ Upstream commit 8ea815399c3fcce1889bd951fec25b5b9a3979c1 ] __ADDRESSABLE_ASM_STR() is where the necessary stringification happens. As long as "sym" doesn't contain any odd characters, no quoting is required for its use with .quad / .long. In fact the quotation gets in the way with gas 2.25; it's only from 2.26 onwards that quoted symbols are half-way properly supported. However, assembly being different from C anyway, drop __ADDRESSABLE_ASM_STR() and its helper macro altogether. A simple .global directive will suffice to get the symbol "declared", i.e. into the symbol table. While there also stop open-coding STATIC_CALL_TRAMP() and STATIC_CALL_KEY(). Fixes: 0ef8047b737d ("x86/static-call: provide a way to do very early static-call updates") Signed-off-by: Jan Beulich Acked-by: Josh Poimboeuf Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross Message-ID: <609d2c74-de13-4fae-ab1a-1ec44afb948d@suse.com> Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

x86/static-call: provide a way to do very early static-call updates

2024-12-19T17:06:13+00:00

commit 0ef8047b737d7480a5d4c46d956e97c190f13050 upstream. Add static_call_update_early() for updating static-call targets in very early boot. This will be needed for support of Xen guest type specific hypercall functions. This is part of XSA-466 / CVE-2024-53241. Reported-by: Andrew Cooper Signed-off-by: Juergen Gross Co-developed-by: Peter Zijlstra Co-developed-by: Josh Poimboeuf Signed-off-by: Greg Kroah-Hartman

compiler.h: Introduce absolute_pointer macro

2021-09-30T08:11:07+00:00

[ Upstream commit f6b5f1a56987de837f8e25cd560847106b8632a8 ] 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 Signed-off-by: Sasha Levin

compiler.h: fix barrier_data() on clang

2020-11-14T19:26:03+00:00

Commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive") neglected to copy barrier_data() from compiler-gcc.h into compiler-clang.h. The definition in compiler-gcc.h was really to work around clang's more aggressive optimization, so this broke barrier_data() on clang, and consequently memzero_explicit() as well. For example, this results in at least the memzero_explicit() call in lib/crypto/sha256.c:sha256_transform() being optimized away by clang. Fix this by moving the definition of barrier_data() into compiler.h. Also move the gcc/clang definition of barrier() into compiler.h, __memory_barrier() is icc-specific (and barrier() is already defined using it in compiler-intel.h) and doesn't belong in compiler.h. [rdunlap@infradead.org: fix ALPHA builds when SMP is not enabled] Link: https://lkml.kernel.org/r/20201101231835.4589-1-rdunlap@infradead.org Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive") Signed-off-by: Arvind Sankar Signed-off-by: Randy Dunlap Signed-off-by: Andrew Morton Tested-by: Nick Desaulniers Reviewed-by: Nick Desaulniers Reviewed-by: Kees Cook Cc: Link: https://lkml.kernel.org/r/20201014212631.207844-1-nivedita@alum.mit.edu Signed-off-by: Linus Torvalds

treewide: Convert macro and uses of section(foo) to section("foo")

2020-10-25T21:51:49+00:00

Use a more generic form for __section that requires quotes to avoid complications with clang and gcc differences. Remove the quote operator # from compiler_attributes.h __section macro. Convert all unquoted __section(foo) uses to quoted __section("foo"). Also convert __attribute__((section("foo"))) uses to __section("foo") even if the __attribute__ has multiple list entry forms. Conversion done using the script at: https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl Signed-off-by: Joe Perches Reviewed-by: Nick Desaulniers Reviewed-by: Miguel Ojeda Signed-off-by: Linus Torvalds

compiler.h: avoid escaped section names

2020-10-14T01:38:26+00:00

The stringification operator, `#`, in the preprocessor escapes strings. For example, `# "foo"` becomes `"\"foo\""`. GCC and Clang differ in how they treat section names that contain \". The portable solution is to not use a string literal with the preprocessor stringification operator. In this case, since __section unconditionally uses the stringification operator, we actually want the more verbose __attribute__((__section__())). Fixes: commit e04462fb82f8 ("Compiler Attributes: remove uses of __attribute__ from compiler.h") Signed-off-by: Nick Desaulniers Signed-off-by: Andrew Morton Cc: Miguel Ojeda Cc: Luc Van Oostenryck Cc: Nathan Chancellor Cc: Arvind Sankar Link: https://bugs.llvm.org/show_bug.cgi?id=42950 Link: https://lkml.kernel.org/r/20200929194318.548707-1-ndesaulniers@google.com Signed-off-by: Linus Torvalds

compiler.h: Make __ADDRESSABLE() symbol truly unique

2020-09-01T07:58:04+00:00

The __ADDRESSABLE() macro uses the __LINE__ macro to create a temporary symbol which has a unique name. However, if the macro is used multiple times from within another macro, the line number will always be the same, resulting in duplicate symbols. Make the temporary symbols truly unique by using __UNIQUE_ID instead of __LINE__. Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Acked-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20200818135804.564436253@infradead.org

Merge tag 'core-headers-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-08-03T21:25:40+00:00

Pull header cleanup from Ingo Molnar: "Separate out the instrumentation_begin()/end() bits from compiler.h" * tag 'core-headers-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: compiler.h: Move instrumentation_begin()/end() to new header