mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-30 22:26:55 +00:00
0d025d271e
There are three usercopy warnings which are currently being silenced for
gcc 4.6 and newer:
1) "copy_from_user() buffer size is too small" compile warning/error
This is a static warning which happens when object size and copy size
are both const, and copy size > object size. I didn't see any false
positives for this one. So the function warning attribute seems to
be working fine here.
Note this scenario is always a bug and so I think it should be
changed to *always* be an error, regardless of
CONFIG_DEBUG_STRICT_USER_COPY_CHECKS.
2) "copy_from_user() buffer size is not provably correct" compile warning
This is another static warning which happens when I enable
__compiletime_object_size() for new compilers (and
CONFIG_DEBUG_STRICT_USER_COPY_CHECKS). It happens when object size
is const, but copy size is *not*. In this case there's no way to
compare the two at build time, so it gives the warning. (Note the
warning is a byproduct of the fact that gcc has no way of knowing
whether the overflow function will be called, so the call isn't dead
code and the warning attribute is activated.)
So this warning seems to only indicate "this is an unusual pattern,
maybe you should check it out" rather than "this is a bug".
I get 102(!) of these warnings with allyesconfig and the
__compiletime_object_size() gcc check removed. I don't know if there
are any real bugs hiding in there, but from looking at a small
sample, I didn't see any. According to Kees, it does sometimes find
real bugs. But the false positive rate seems high.
3) "Buffer overflow detected" runtime warning
This is a runtime warning where object size is const, and copy size >
object size.
All three warnings (both static and runtime) were completely disabled
for gcc 4.6 with the following commit:
2fb0815c9e ("gcc4: disable __compiletime_object_size for GCC 4.6+")
That commit mistakenly assumed that the false positives were caused by a
gcc bug in __compiletime_object_size(). But in fact,
__compiletime_object_size() seems to be working fine. The false
positives were instead triggered by #2 above. (Though I don't have an
explanation for why the warnings supposedly only started showing up in
gcc 4.6.)
So remove warning #2 to get rid of all the false positives, and re-enable
warnings #1 and #3 by reverting the above commit.
Furthermore, since #1 is a real bug which is detected at compile time,
upgrade it to always be an error.
Having done all that, CONFIG_DEBUG_STRICT_USER_COPY_CHECKS is no longer
needed.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
288 lines
9.7 KiB
C
288 lines
9.7 KiB
C
#ifndef __LINUX_COMPILER_H
|
|
#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
|
|
#endif
|
|
|
|
/*
|
|
* Common definitions for all gcc versions go here.
|
|
*/
|
|
#define GCC_VERSION (__GNUC__ * 10000 \
|
|
+ __GNUC_MINOR__ * 100 \
|
|
+ __GNUC_PATCHLEVEL__)
|
|
|
|
/* Optimization barrier */
|
|
|
|
/* The "volatile" is due to gcc bugs */
|
|
#define barrier() __asm__ __volatile__("": : :"memory")
|
|
/*
|
|
* This version is i.e. to prevent dead stores elimination on @ptr
|
|
* where gcc and llvm may behave differently when otherwise using
|
|
* normal barrier(): while gcc behavior gets along with a normal
|
|
* barrier(), llvm needs an explicit input variable to be assumed
|
|
* clobbered. The issue is as follows: while the inline asm might
|
|
* access any memory it wants, the compiler could have fit all of
|
|
* @ptr into memory registers instead, and since @ptr never escaped
|
|
* from that, it proofed that the inline asm wasn't touching any of
|
|
* it. This version works well with both compilers, i.e. we're telling
|
|
* the compiler that the inline asm absolutely may see the contents
|
|
* of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
|
|
*/
|
|
#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
|
|
|
|
/*
|
|
* This macro obfuscates arithmetic on a variable address so that gcc
|
|
* shouldn't recognize the original var, and make assumptions about it.
|
|
*
|
|
* This is needed because the C standard makes it undefined to do
|
|
* pointer arithmetic on "objects" outside their boundaries and the
|
|
* gcc optimizers assume this is the case. In particular they
|
|
* assume such arithmetic does not wrap.
|
|
*
|
|
* A miscompilation has been observed because of this on PPC.
|
|
* To work around it we hide the relationship of the pointer and the object
|
|
* using this macro.
|
|
*
|
|
* Versions of the ppc64 compiler before 4.1 had a bug where use of
|
|
* RELOC_HIDE could trash r30. The bug can be worked around by changing
|
|
* the inline assembly constraint from =g to =r, in this particular
|
|
* case either is valid.
|
|
*/
|
|
#define RELOC_HIDE(ptr, off) \
|
|
({ \
|
|
unsigned long __ptr; \
|
|
__asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
|
|
(typeof(ptr)) (__ptr + (off)); \
|
|
})
|
|
|
|
/* Make the optimizer believe the variable can be manipulated arbitrarily. */
|
|
#define OPTIMIZER_HIDE_VAR(var) \
|
|
__asm__ ("" : "=r" (var) : "0" (var))
|
|
|
|
#ifdef __CHECKER__
|
|
#define __must_be_array(a) 0
|
|
#else
|
|
/* &a[0] degrades to a pointer: a different type from an array */
|
|
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
|
|
#endif
|
|
|
|
/*
|
|
* Force always-inline if the user requests it so via the .config,
|
|
* or if gcc is too old:
|
|
*/
|
|
#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
|
|
!defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
|
|
#define inline inline __attribute__((always_inline)) notrace
|
|
#define __inline__ __inline__ __attribute__((always_inline)) notrace
|
|
#define __inline __inline __attribute__((always_inline)) notrace
|
|
#else
|
|
/* A lot of inline functions can cause havoc with function tracing */
|
|
#define inline inline notrace
|
|
#define __inline__ __inline__ notrace
|
|
#define __inline __inline notrace
|
|
#endif
|
|
|
|
#define __always_inline inline __attribute__((always_inline))
|
|
#define noinline __attribute__((noinline))
|
|
|
|
#define __deprecated __attribute__((deprecated))
|
|
#define __packed __attribute__((packed))
|
|
#define __weak __attribute__((weak))
|
|
#define __alias(symbol) __attribute__((alias(#symbol)))
|
|
|
|
/*
|
|
* it doesn't make sense on ARM (currently the only user of __naked)
|
|
* to trace naked functions because then mcount is called without
|
|
* stack and frame pointer being set up and there is no chance to
|
|
* restore the lr register to the value before mcount was called.
|
|
*
|
|
* The asm() bodies of naked functions often depend on standard calling
|
|
* conventions, therefore they must be noinline and noclone.
|
|
*
|
|
* GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
|
|
* See GCC PR44290.
|
|
*/
|
|
#define __naked __attribute__((naked)) noinline __noclone notrace
|
|
|
|
#define __noreturn __attribute__((noreturn))
|
|
|
|
/*
|
|
* From the GCC manual:
|
|
*
|
|
* Many functions have no effects except the return value and their
|
|
* return value depends only on the parameters and/or global
|
|
* variables. Such a function can be subject to common subexpression
|
|
* elimination and loop optimization just as an arithmetic operator
|
|
* would be.
|
|
* [...]
|
|
*/
|
|
#define __pure __attribute__((pure))
|
|
#define __aligned(x) __attribute__((aligned(x)))
|
|
#define __printf(a, b) __attribute__((format(printf, a, b)))
|
|
#define __scanf(a, b) __attribute__((format(scanf, a, b)))
|
|
#define __attribute_const__ __attribute__((__const__))
|
|
#define __maybe_unused __attribute__((unused))
|
|
#define __always_unused __attribute__((unused))
|
|
|
|
/* gcc version specific checks */
|
|
|
|
#if GCC_VERSION < 30200
|
|
# error Sorry, your compiler is too old - please upgrade it.
|
|
#endif
|
|
|
|
#if GCC_VERSION < 30300
|
|
# define __used __attribute__((__unused__))
|
|
#else
|
|
# define __used __attribute__((__used__))
|
|
#endif
|
|
|
|
#ifdef CONFIG_GCOV_KERNEL
|
|
# if GCC_VERSION < 30400
|
|
# error "GCOV profiling support for gcc versions below 3.4 not included"
|
|
# endif /* __GNUC_MINOR__ */
|
|
#endif /* CONFIG_GCOV_KERNEL */
|
|
|
|
#if GCC_VERSION >= 30400
|
|
#define __must_check __attribute__((warn_unused_result))
|
|
#define __malloc __attribute__((__malloc__))
|
|
#endif
|
|
|
|
#if GCC_VERSION >= 40000
|
|
|
|
/* GCC 4.1.[01] miscompiles __weak */
|
|
#ifdef __KERNEL__
|
|
# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
|
|
# error Your version of gcc miscompiles the __weak directive
|
|
# endif
|
|
#endif
|
|
|
|
#define __used __attribute__((__used__))
|
|
#define __compiler_offsetof(a, b) \
|
|
__builtin_offsetof(a, b)
|
|
|
|
#if GCC_VERSION >= 40100
|
|
# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
|
|
#endif
|
|
|
|
#if GCC_VERSION >= 40300
|
|
/* Mark functions as cold. gcc will assume any path leading to a call
|
|
* to them will be unlikely. This means a lot of manual unlikely()s
|
|
* are unnecessary now for any paths leading to the usual suspects
|
|
* like BUG(), printk(), panic() etc. [but let's keep them for now for
|
|
* older compilers]
|
|
*
|
|
* Early snapshots of gcc 4.3 don't support this and we can't detect this
|
|
* in the preprocessor, but we can live with this because they're unreleased.
|
|
* Maketime probing would be overkill here.
|
|
*
|
|
* gcc also has a __attribute__((__hot__)) to move hot functions into
|
|
* a special section, but I don't see any sense in this right now in
|
|
* the kernel context
|
|
*/
|
|
#define __cold __attribute__((__cold__))
|
|
|
|
#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
|
|
|
|
#ifndef __CHECKER__
|
|
# define __compiletime_warning(message) __attribute__((warning(message)))
|
|
# define __compiletime_error(message) __attribute__((error(message)))
|
|
#endif /* __CHECKER__ */
|
|
#endif /* GCC_VERSION >= 40300 */
|
|
|
|
#if GCC_VERSION >= 40500
|
|
/*
|
|
* Mark a position in code as unreachable. This can be used to
|
|
* suppress control flow warnings after asm blocks that transfer
|
|
* control elsewhere.
|
|
*
|
|
* Early snapshots of gcc 4.5 don't support this and we can't detect
|
|
* this in the preprocessor, but we can live with this because they're
|
|
* unreleased. Really, we need to have autoconf for the kernel.
|
|
*/
|
|
#define unreachable() __builtin_unreachable()
|
|
|
|
/* Mark a function definition as prohibited from being cloned. */
|
|
#define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
|
|
|
|
#endif /* GCC_VERSION >= 40500 */
|
|
|
|
#if GCC_VERSION >= 40600
|
|
/*
|
|
* When used with Link Time Optimization, gcc can optimize away C functions or
|
|
* variables which are referenced only from assembly code. __visible tells the
|
|
* optimizer that something else uses this function or variable, thus preventing
|
|
* this.
|
|
*/
|
|
#define __visible __attribute__((externally_visible))
|
|
#endif
|
|
|
|
|
|
#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
|
|
/*
|
|
* __assume_aligned(n, k): Tell the optimizer that the returned
|
|
* pointer can be assumed to be k modulo n. The second argument is
|
|
* optional (default 0), so we use a variadic macro to make the
|
|
* shorthand.
|
|
*
|
|
* Beware: Do not apply this to functions which may return
|
|
* ERR_PTRs. Also, it is probably unwise to apply it to functions
|
|
* returning extra information in the low bits (but in that case the
|
|
* compiler should see some alignment anyway, when the return value is
|
|
* massaged by 'flags = ptr & 3; ptr &= ~3;').
|
|
*/
|
|
#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
|
|
#endif
|
|
|
|
/*
|
|
* GCC 'asm goto' miscompiles certain code sequences:
|
|
*
|
|
* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
|
|
*
|
|
* Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
|
|
*
|
|
* (asm goto is automatically volatile - the naming reflects this.)
|
|
*/
|
|
#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
|
|
|
|
/*
|
|
* sparse (__CHECKER__) pretends to be gcc, but can't do constant
|
|
* folding in __builtin_bswap*() (yet), so don't set these for it.
|
|
*/
|
|
#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
|
|
#if GCC_VERSION >= 40400
|
|
#define __HAVE_BUILTIN_BSWAP32__
|
|
#define __HAVE_BUILTIN_BSWAP64__
|
|
#endif
|
|
#if GCC_VERSION >= 40800
|
|
#define __HAVE_BUILTIN_BSWAP16__
|
|
#endif
|
|
#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
|
|
|
|
#if GCC_VERSION >= 50000
|
|
#define KASAN_ABI_VERSION 4
|
|
#elif GCC_VERSION >= 40902
|
|
#define KASAN_ABI_VERSION 3
|
|
#endif
|
|
|
|
#if GCC_VERSION >= 40902
|
|
/*
|
|
* Tell the compiler that address safety instrumentation (KASAN)
|
|
* should not be applied to that function.
|
|
* Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
|
|
*/
|
|
#define __no_sanitize_address __attribute__((no_sanitize_address))
|
|
#endif
|
|
|
|
#endif /* gcc version >= 40000 specific checks */
|
|
|
|
#if !defined(__noclone)
|
|
#define __noclone /* not needed */
|
|
#endif
|
|
|
|
#if !defined(__no_sanitize_address)
|
|
#define __no_sanitize_address
|
|
#endif
|
|
|
|
/*
|
|
* A trick to suppress uninitialized variable warning without generating any
|
|
* code
|
|
*/
|
|
#define uninitialized_var(x) x = x
|