user/sven/linux.git/include/linux/compiler-gcc.h, branch v4.9.109

complete e390f9a port for v4.9.106

2018-06-13T14:16:44Z

objtool ports introduced in v4.9.106 were not totally complete. Therefore they resulted in issues like: module: overflow in relocation type 10 val XXXXXXXXXXX ‘usbcore’ likely not compiled with -mcmodel=kernel module: overflow in relocation type 10 val XXXXXXXXXXX ‘scsi_mod’ likely not compiled with -mcmodel=kernel Missing part was the complete backport of commit e390f9a. Original notes by Josh Poimboeuf: The '__unreachable' and '__func_stack_frame_non_standard' sections are only used at compile time. They're discarded for vmlinux but they should also be discarded for modules. Since this is a recurring pattern, prefix the section names with ".discard.". It's a nice convention and vmlinux.lds.h already discards such sections. Also remove the 'a' (allocatable) flag from the __unreachable section since it doesn't make sense for a discarded section. Signed-off-by: Philip Müller Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends") Link: https://gitlab.manjaro.org/packages/core/linux49/issues/2 Signed-off-by: Greg Kroah-Hartman

objtool: Enclose contents of unreachable() macro in a block

2018-06-05T08:28:58Z

commit 4e4636cf981b5b629fbfb78aa9f232e015f7d521 upstream. Guenter Roeck reported a boot failure in mips64. It was bisected to the following commit: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends") The unreachable() macro was formerly only composed of a single statement. The above commit added a second statement, but neglected to enclose the statements in a block. Suggested-by: Guenter Roeck Reported-by: Guenter Roeck Signed-off-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends") Link: http://lkml.kernel.org/r/20170228042116.glmwmwiohcix7o4a@treble Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

objtool: Improve detection of BUG() and other dead ends

2018-06-05T08:28:55Z

commit d1091c7fa3d52ebce4dd3f15d04155b3469b2f90 upstream. The BUG() macro's use of __builtin_unreachable() via the unreachable() macro tells gcc that the instruction is a dead end, and that it's safe to assume the current code path will not execute past the previous instruction. On x86, the BUG() macro is implemented with the 'ud2' instruction. When objtool's branch analysis sees that instruction, it knows the current code path has come to a dead end. Peter Zijlstra has been working on a patch to change the WARN macros to use 'ud2'. That patch will break objtool's assumption that 'ud2' is always a dead end. Generally it's best for objtool to avoid making those kinds of assumptions anyway. The more ignorant it is of kernel code internals, the better. So create a more generic way for objtool to detect dead ends by adding an annotation to the unreachable() macro. The annotation stores a pointer to the end of the unreachable code path in an '__unreachable' section. Objtool can read that section to find the dead ends. Tested-by: Peter Zijlstra (Intel) Signed-off-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/41a6d33971462ebd944a1c60ad4bf5be86c17b77.1487712920.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86/retpoline: Support retpoline builds with Clang

2018-03-18T10:18:52Z

commit 87358710c1fb4f1bf96bbe2349975ff9953fc9b2 upstream. Signed-off-by: David Woodhouse Reviewed-by: Thomas Gleixner Cc: Linus Torvalds Cc: Peter Zijlstra Cc: arjan.van.de.ven@intel.com Cc: bp@alien8.de Cc: dave.hansen@intel.com Cc: jmattson@google.com Cc: karahmed@amazon.de Cc: kvm@vger.kernel.org Cc: pbonzini@redhat.com Cc: rkrcmar@redhat.com Link: http://lkml.kernel.org/r/1519037457-7643-5-git-send-email-dwmw@amazon.co.uk Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

compiler-gcc.h: Introduce __optimize function attribute

2018-02-22T14:43:53Z

commit df5d45aa08f848b79caf395211b222790534ccc7 upstream. Create a new function attribute __optimize, which allows to specify an optimization level on a per-function basis. Signed-off-by: Geert Uytterhoeven Acked-by: Ard Biesheuvel Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman

kasan: update kasan_global for gcc 7

2016-12-01T00:32:52Z

kasan_global struct is part of compiler/runtime ABI. gcc revision 241983 has added a new field to kasan_global struct. Update kernel definition of kasan_global struct to include the new field. Without this patch KASAN is broken with gcc 7. Link: http://lkml.kernel.org/r/1479219743-28682-1-git-send-email-dvyukov@google.com Signed-off-by: Dmitry Vyukov Acked-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: [4.0+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

latent_entropy: Mark functions with __latent_entropy

2016-10-10T21:51:45Z

The __latent_entropy gcc attribute can be used only on functions and variables. If it is on a function then the plugin will instrument it for gathering control-flow entropy. If the attribute is on a variable then the plugin will initialize it with random contents. The variable must be an integer, an integer array type or a structure with integer fields. These specific functions have been selected because they are init functions (to help gather boot-time entropy), are called at unpredictable times, or they have variable loops, each of which provide some level of latent entropy. Signed-off-by: Emese Revfy [kees: expanded commit message] Signed-off-by: Kees Cook

mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS

2016-08-30T17:10:21Z

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: 2fb0815c9ee6 ("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 Cc: Kees Cook Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H . Peter Anvin" Cc: Andy Lutomirski Cc: Steven Rostedt Cc: Brian Gerst Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: Byungchul Park Cc: Nilay Vaish Signed-off-by: Linus Torvalds

byteswap: don't use __builtin_bswap*() with sparse

2016-08-27T00:39:34Z

Although sparse declares __builtin_bswap*(), it can't actually do constant folding inside them (yet). As such, things like switch (protocol) { case htons(ETH_P_IP): break; } which we do all over the place cause sparse to warn that it expects a constant instead of a function call. Disable __HAVE_BUILTIN_BSWAP*__ if __CHECKER__ is defined to avoid this. Fixes: 7322dd755e7d ("byteswap: try to avoid __builtin_constant_p gcc bug") Link: http://lkml.kernel.org/r/1470914102-26389-1-git-send-email-johannes@sipsolutions.net Signed-off-by: Johannes Berg Acked-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

compiler.h: add support for malloc attribute

2016-05-20T02:12:14Z

gcc as far back as at least 3.04 documents the function attribute __malloc__. Add a shorthand for attaching that to a function declaration. This was also suggested by Andi Kleen way back in 2002 [1], but didn't get applied, perhaps because gcc at that time generated the exact same code with and without this attribute. This attribute tells the compiler that the return value (if non-NULL) can be assumed not to alias any other valid pointers at the time of the call. Please note that the documentation for a range of gcc versions (starting from around 4.7) contained a somewhat confusing and self-contradicting text: The malloc attribute is used to tell the compiler that a function may be treated as if any non-NULL pointer it returns cannot alias any other pointer valid when the function returns and *that the memory has undefined content*. [...] Standard functions with this property include malloc and *calloc*. (emphasis mine). The intended meaning has later been clarified [2]: This tells the compiler that a function is malloc-like, i.e., that the pointer P returned by the function cannot alias any other pointer valid when the function returns, and moreover no pointers to valid objects occur in any storage addressed by P. What this means is that we can apply the attribute to kmalloc and friends, and it is ok for the returned memory to have well-defined contents (__GFP_ZERO). But it is not ok to apply it to kmemdup(), nor to other functions which both allocate and possibly initialize the memory with existing pointers. So unless someone is doing something pretty perverted kstrdup() should also be a fine candidate. [1] http://thread.gmane.org/gmane.linux.kernel/57172 [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56955 Signed-off-by: Rasmus Villemoes Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds