Merge tag 'clang-features-v5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull clang feature updates from Kees Cook:

 - Add CC_HAS_NO_PROFILE_FN_ATTR in preparation for PGO support in the
   face of the noinstr attribute, paving the way for PGO and fixing
   GCOV. (Nick Desaulniers)

 - x86_64 LTO coverage is expanded to 32-bit x86. (Nathan Chancellor)

 - Small fixes to CFI. (Mark Rutland, Nathan Chancellor)

* tag 'clang-features-v5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  qemu_fw_cfg: Make fw_cfg_rev_attr a proper kobj_attribute
  Kconfig: Introduce ARCH_WANTS_NO_INSTR and CC_HAS_NO_PROFILE_FN_ATTR
  compiler_attributes.h: cleanups for GCC 4.9+
  compiler_attributes.h: define __no_profile, add to noinstr
  x86, lto: Enable Clang LTO for 32-bit as well
  CFI: Move function_nocfi() into compiler.h
  MAINTAINERS: Add Clang CFI section

MAINTAINERS

@@ -4447,6 +4447,18 @@ F:	include/linux/compiler-clang.h
 F:	scripts/clang-tools/
 K:	\b(?i:clang|llvm)\b
 
+CLANG CONTROL FLOW INTEGRITY SUPPORT
+M:	Sami Tolvanen <samitolvanen@google.com>
+M:	Kees Cook <keescook@chromium.org>
+R:	Nathan Chancellor <nathan@kernel.org>
+R:	Nick Desaulniers <ndesaulniers@google.com>
+L:	clang-built-linux@googlegroups.com
+S:	Supported
+B:	https://github.com/ClangBuiltLinux/linux/issues
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/clang/features
+F:	include/linux/cfi.h
+F:	kernel/cfi.c
+
 CLEANCACHE API
 M:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
 L:	linux-kernel@vger.kernel.org

arch/Kconfig

@@ -285,6 +285,13 @@ config ARCH_THREAD_STACK_ALLOCATOR
 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 	bool
 
+config ARCH_WANTS_NO_INSTR
+	bool
+	help
+	  An architecture should select this if the noinstr macro is being used on
+	  functions to denote that the toolchain should avoid instrumenting such
+	  functions and is required for correctness.
+
 config ARCH_32BIT_OFF_T
 	bool
 	depends on !64BIT

arch/arm64/Kconfig

@@ -93,6 +93,7 @@ config ARM64
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
 	select ARCH_WANT_LD_ORPHAN_WARN
+	select ARCH_WANTS_NO_INSTR
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARM_AMBA
 	select ARM_ARCH_TIMER

arch/arm64/include/asm/compiler.h

@@ -23,4 +23,20 @@
 #define __builtin_return_address(val)					\
 	(void *)(ptrauth_clear_pac((unsigned long)__builtin_return_address(val)))
 
+#ifdef CONFIG_CFI_CLANG
+/*
+ * With CONFIG_CFI_CLANG, the compiler replaces function address
+ * references with the address of the function's CFI jump table
+ * entry. The function_nocfi macro always returns the address of the
+ * actual function instead.
+ */
+#define function_nocfi(x) ({						\
+	void *addr;							\
+	asm("adrp %0, " __stringify(x) "\n\t"				\
+	    "add  %0, %0, :lo12:" __stringify(x)			\
+	    : "=r" (addr));						\
+	addr;								\
+})
+#endif
+
 #endif /* __ASM_COMPILER_H */

arch/arm64/include/asm/memory.h

@@ -321,22 +321,6 @@ static inline void *phys_to_virt(phys_addr_t x)
 #define virt_to_pfn(x)		__phys_to_pfn(__virt_to_phys((unsigned long)(x)))
 #define sym_to_pfn(x)		__phys_to_pfn(__pa_symbol(x))
 
-#ifdef CONFIG_CFI_CLANG
-/*
- * With CONFIG_CFI_CLANG, the compiler replaces function address
- * references with the address of the function's CFI jump table
- * entry. The function_nocfi macro always returns the address of the
- * actual function instead.
- */
-#define function_nocfi(x) ({						\
-	void *addr;							\
-	asm("adrp %0, " __stringify(x) "\n\t"				\
-	    "add  %0, %0, :lo12:" __stringify(x)			\
-	    : "=r" (addr));						\
-	addr;								\
-})
-#endif
-
 /*
  *  virt_to_page(x)	convert a _valid_ virtual address to struct page *
  *  virt_addr_valid(x)	indicates whether a virtual address is valid

arch/s390/Kconfig

@@ -117,6 +117,7 @@ config S390
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_WANTS_DYNAMIC_TASK_STRUCT
+	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_DEFAULT_BPF_JIT
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_TABLE_SORT

arch/x86/Kconfig

@@ -103,8 +103,8 @@ config X86
 	select ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	select ARCH_SUPPORTS_NUMA_BALANCING	if X86_64
 	select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP	if NR_CPUS <= 4096
-	select ARCH_SUPPORTS_LTO_CLANG		if X86_64
-	select ARCH_SUPPORTS_LTO_CLANG_THIN	if X86_64
+	select ARCH_SUPPORTS_LTO_CLANG
+	select ARCH_SUPPORTS_LTO_CLANG_THIN
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_MEMTEST
 	select ARCH_USE_QUEUED_RWLOCKS
@@ -113,6 +113,7 @@ config X86
 	select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 	select ARCH_WANT_DEFAULT_BPF_JIT	if X86_64
 	select ARCH_WANTS_DYNAMIC_TASK_STRUCT
+	select ARCH_WANTS_NO_INSTR
 	select ARCH_WANT_HUGE_PMD_SHARE
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANTS_THP_SWAP		if X86_64

drivers/firmware/qemu_fw_cfg.c

@@ -299,15 +299,13 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev)
 	return 0;
 }
 
-static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf)
+static ssize_t fw_cfg_showrev(struct kobject *k, struct kobj_attribute *a,
+			      char *buf)
 {
 	return sprintf(buf, "%u\n", fw_cfg_rev);
 }
 
-static const struct {
-	struct attribute attr;
-	ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf);
-} fw_cfg_rev_attr = {
+static const struct kobj_attribute fw_cfg_rev_attr = {
 	.attr = { .name = "rev", .mode = S_IRUSR },
 	.show = fw_cfg_showrev,
 };

include/linux/compiler.h

@@ -219,6 +219,16 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 	__v;								\
 })
 
+/*
+ * With CONFIG_CFI_CLANG, the compiler replaces function addresses in
+ * instrumented C code with jump table addresses. Architectures that
+ * support CFI can define this macro to return the actual function address
+ * when needed.
+ */
+#ifndef function_nocfi
+#define function_nocfi(x) (x)
+#endif
+
 #endif /* __KERNEL__ */
 
 /*

include/linux/compiler_attributes.h

@@ -27,15 +27,16 @@
  */
 #ifndef __has_attribute
 # define __has_attribute(x) __GCC4_has_attribute_##x
-# define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
+# define __GCC4_has_attribute___assume_aligned__      1
 # define __GCC4_has_attribute___copy__                0
 # define __GCC4_has_attribute___designated_init__     0
 # define __GCC4_has_attribute___externally_visible__  1
 # define __GCC4_has_attribute___no_caller_saved_registers__ 0
 # define __GCC4_has_attribute___noclone__             1
+# define __GCC4_has_attribute___no_profile_instrument_function__ 0
 # define __GCC4_has_attribute___nonstring__           0
-# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
-# define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
+# define __GCC4_has_attribute___no_sanitize_address__ 1
+# define __GCC4_has_attribute___no_sanitize_undefined__ 1
 # define __GCC4_has_attribute___fallthrough__         0
 #endif
 
@@ -238,6 +239,18 @@
 # define __nonstring
 #endif
 
+/*
+ * Optional: only supported since GCC >= 7.1, clang >= 13.0.
+ *
+ *      gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fprofile_005finstrument_005ffunction-function-attribute
+ *    clang: https://clang.llvm.org/docs/AttributeReference.html#no-profile-instrument-function
+ */
+#if __has_attribute(__no_profile_instrument_function__)
+# define __no_profile                  __attribute__((__no_profile_instrument_function__))
+#else
+# define __no_profile
+#endif
+
 /*
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn

include/linux/compiler_types.h

@@ -210,7 +210,7 @@ struct ftrace_likely_data {
 /* Section for code which can't be instrumented at all */
 #define noinstr								\
 	noinline notrace __attribute((__section__(".noinstr.text")))	\
-	__no_kcsan __no_sanitize_address
+	__no_kcsan __no_sanitize_address __no_profile
 
 #endif /* __KERNEL__ */
 

include/linux/mm.h

@@ -124,16 +124,6 @@ extern int mmap_rnd_compat_bits __read_mostly;
 #define lm_alias(x)	__va(__pa_symbol(x))
 #endif
 
-/*
- * With CONFIG_CFI_CLANG, the compiler replaces function addresses in
- * instrumented C code with jump table addresses. Architectures that
- * support CFI can define this macro to return the actual function address
- * when needed.
- */
-#ifndef function_nocfi
-#define function_nocfi(x) (x)
-#endif
-
 /*
  * To prevent common memory management code establishing
  * a zero page mapping on a read fault.

init/Kconfig

@@ -83,6 +83,9 @@ config TOOLS_SUPPORT_RELR
 config CC_HAS_ASM_INLINE
 	def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
 
+config CC_HAS_NO_PROFILE_FN_ATTR
+	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
+
 config CONSTRUCTORS
 	bool
 

kernel/gcov/Kconfig

@@ -5,6 +5,7 @@ config GCOV_KERNEL
 	bool "Enable gcov-based kernel profiling"
 	depends on DEBUG_FS
 	depends on !CC_IS_CLANG || CLANG_VERSION >= 110000
+	depends on !ARCH_WANTS_NO_INSTR || CC_HAS_NO_PROFILE_FN_ATTR
 	select CONSTRUCTORS
 	default n
 	help