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Clang feature updates for v5.14-rc1

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- 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)
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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
This commit is contained in:
Linus Torvalds 2021-06-30 14:33:25 -07:00
commit 44b6ed4cfa
14 changed files with 74 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
MAINTAINERS
View File

@ -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

7
arch/Kconfig
View File

@ -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

1
arch/arm64/Kconfig
View File

@ -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

16
arch/arm64/include/asm/compiler.h
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@ -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 */

16
arch/arm64/include/asm/memory.h
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@ -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

1
arch/s390/Kconfig
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@ -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

5
arch/x86/Kconfig
View File

@ -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

8
drivers/firmware/qemu_fw_cfg.c
View File

@ -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,
};

10
include/linux/compiler.h
View File

@ -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__ */
/*

19
include/linux/compiler_attributes.h
View File

@ -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

2
include/linux/compiler_types.h
View File

@ -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__ */

10
include/linux/mm.h
View File

@ -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.

3
init/Kconfig
View File

@ -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

1
kernel/gcov/Kconfig
View File

@ -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