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GCC 4.6 is not supported anymore, so remove a reference to it,
leaving just the part about version prior GCC 5.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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Sparse supports __has_attribute() since 2018-08-31, so the comment
is not true anymore but more importantly is rather confusing.
So remove it.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull gcc plugin updates from Kees Cook:
"Primarily improvements to STACKLEAK from Alexander Popov, along with
some additional cleanups.
- Update URLs for HTTPS scheme where available (Alexander A. Klimov)
- Improve STACKLEAK code generation on x86 (Alexander Popov)"
* tag 'gcc-plugins-v5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
gcc-plugins: Replace HTTP links with HTTPS ones
gcc-plugins/stackleak: Add 'verbose' plugin parameter
gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving
ARM: vdso: Don't use gcc plugins for building vgettimeofday.c
gcc-plugins/stackleak: Don't instrument itself
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The kernel code instrumentation in stackleak gcc plugin works in two stages.
At first, stack tracking is added to GIMPLE representation of every function
(except some special cases). And later, when stack frame size info is
available, stack tracking is removed from the RTL representation of the
functions with small stack frame. There is an unwanted side-effect for these
functions: some of them do useless work with caller-saved registers.
As an example of such case, proc_sys_write without() instrumentation:
55 push %rbp
41 b8 01 00 00 00 mov $0x1,%r8d
48 89 e5 mov %rsp,%rbp
e8 11 ff ff ff callq ffffffff81284610 <proc_sys_call_handler>
5d pop %rbp
c3 retq
0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
00 00 00
proc_sys_write() with instrumentation:
55 push %rbp
48 89 e5 mov %rsp,%rbp
41 56 push %r14
41 55 push %r13
41 54 push %r12
53 push %rbx
49 89 f4 mov %rsi,%r12
48 89 fb mov %rdi,%rbx
49 89 d5 mov %rdx,%r13
49 89 ce mov %rcx,%r14
4c 89 f1 mov %r14,%rcx
4c 89 ea mov %r13,%rdx
4c 89 e6 mov %r12,%rsi
48 89 df mov %rbx,%rdi
41 b8 01 00 00 00 mov $0x1,%r8d
e8 f2 fe ff ff callq ffffffff81298e80 <proc_sys_call_handler>
5b pop %rbx
41 5c pop %r12
41 5d pop %r13
41 5e pop %r14
5d pop %rbp
c3 retq
66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
00 00
Let's improve the instrumentation to avoid this:
1. Make stackleak_track_stack() save all register that it works with.
Use no_caller_saved_registers attribute for that function. This attribute
is available for x86_64 and i386 starting from gcc-7.
2. Insert calling stackleak_track_stack() in asm:
asm volatile("call stackleak_track_stack" :: "r" (current_stack_pointer))
Here we use ASM_CALL_CONSTRAINT trick from arch/x86/include/asm/asm.h.
The input constraint is taken into account during gcc shrink-wrapping
optimization. It is needed to be sure that stackleak_track_stack() call is
inserted after the prologue of the containing function, when the stack
frame is prepared.
This work is a deep reengineering of the idea described on grsecurity blog
https://grsecurity.net/resolving_an_unfortunate_stackleak_interaction
Signed-off-by: Alexander Popov <alex.popov@linux.com>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: https://lore.kernel.org/r/20200624123330.83226-5-alex.popov@linux.com
Signed-off-by: Kees Cook <keescook@chromium.org>
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UBSAN is supported since GCC 4.9, which unfortunately did not yet have
__has_attribute(). To work around, the __GCC4_has_attribute workaround
requires defining which compiler version supports the given attribute.
In the case of no_sanitize_undefined, it is the first version that
supports UBSAN, which is GCC 4.9.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: https://lkml.kernel.org/r/20200615231529.GA119644@google.com
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Reserve the pseudo keyword 'fallthrough' for the ability to convert the
various case block /* fallthrough */ style comments to appear to be an
actual reserved word with the same gcc case block missing fallthrough
warning capability.
All switch/case blocks now should end in one of:
break;
fallthrough;
goto <label>;
return [expression];
continue;
In C mode, GCC supports the __fallthrough__ attribute since 7.1,
the same time the warning and the comment parsing were introduced.
fallthrough devolves to an empty "do {} while (0)" if the compiler
version (any version less than gcc 7) does not support the attribute.
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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From the GCC manual:
copy
copy(function)
The copy attribute applies the set of attributes with which function
has been declared to the declaration of the function to which
the attribute is applied. The attribute is designed for libraries
that define aliases or function resolvers that are expected
to specify the same set of attributes as their targets. The copy
attribute can be used with functions, variables, or types. However,
the kind of symbol to which the attribute is applied (either
function or variable) must match the kind of symbol to which
the argument refers. The copy attribute copies only syntactic and
semantic attributes but not attributes that affect a symbol’s
linkage or visibility such as alias, visibility, or weak.
The deprecated attribute is also not copied.
https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
The upcoming GCC 9 release extends the -Wmissing-attributes warnings
(enabled by -Wall) to C and aliases: it warns when particular function
attributes are missing in the aliases but not in their target, e.g.:
void __cold f(void) {}
void __alias("f") g(void);
diagnoses:
warning: 'g' specifies less restrictive attribute than
its target 'f': 'cold' [-Wmissing-attributes]
Using __copy(f) we can copy the __cold attribute from f to g:
void __cold f(void) {}
void __copy(f) __alias("f") g(void);
This attribute is most useful to deal with situations where an alias
is declared but we don't know the exact attributes the target has.
For instance, in the kernel, the widely used module_init/exit macros
define the init/cleanup_module aliases, but those cannot be marked
always as __init/__exit since some modules do not have their
functions marked as such.
Suggested-by: Martin Sebor <msebor@gcc.gnu.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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This commit splits the current CONFIG_KASAN config option into two:
1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one
that exists now);
2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode.
The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have
another hardware tag-based KASAN mode, that will rely on hardware memory
tagging support in arm64.
With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to
instrument kernel files with -fsantize=kernel-hwaddress (except the ones
for which KASAN_SANITIZE := n is set).
Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both
CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes.
This commit also adds empty placeholder (for now) implementation of
tag-based KASAN specific hooks inserted by the compiler and adjusts
common hooks implementation.
While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option
is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will
enable once all the infrastracture code has been added.
Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The -ftracer optimization was disabled in __noclone as a workaround to
GCC duplicating a blob of inline assembly that happened to define a
global variable. It has been pointed out that no amount of workarounds
can guarantee the compiler won't duplicate inline assembly[1], and that
disabling the -ftracer optimization has several unintended and nasty
side effects[2][3].
Now that the offending KVM code which required the workaround has
been properly fixed and no longer uses __noclone, remove the -ftracer
optimization tweak from __noclone.
[1] https://lore.kernel.org/lkml/ri6y38lo23g.fsf@suse.cz/T/#u
[2] https://lore.kernel.org/lkml/20181218140105.ajuiglkpvstt3qxs@treble/T/#u
[3] https://patchwork.kernel.org/patch/8707981/#21817015
This reverts commit 95272c29378ee7dc15f43fa2758cb28a5913a06d.
Suggested-by: Andi Kleen <ak@linux.intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Martin Jambor <mjambor@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Explain better what "optional" attributes are, and avoid calling
them so to avoid confusion. Simply retain "Optional" as a word
to look for in the comments.
Moreover, add a couple sentences to explain a bit more the intention
and the documentation links.
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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From the GCC manual:
nonstring
The nonstring variable attribute specifies that an object or member
declaration with type array of char, signed char, or unsigned char,
or pointer to such a type is intended to store character arrays that
do not necessarily contain a terminating NUL. This is useful in detecting
uses of such arrays or pointers with functions that expect NUL-terminated
strings, and to avoid warnings when such an array or pointer is used as
an argument to a bounded string manipulation function such as strncpy.
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html
This attribute can be used for documentation purposes (i.e. replacing
comments), but it is most helpful when the following warnings are enabled:
-Wstringop-overflow
Warn for calls to string manipulation functions such as memcpy and
strcpy that are determined to overflow the destination buffer.
[...]
-Wstringop-truncation
Warn for calls to bounded string manipulation functions such as
strncat, strncpy, and stpncpy that may either truncate the copied
string or leave the destination unchanged.
[...]
In situations where a character array is intended to store a sequence
of bytes with no terminating NUL such an array may be annotated with
attribute nonstring to avoid this warning. Such arrays, however,
are not suitable arguments to functions that expect NUL-terminated
strings. To help detect accidental misuses of such arrays GCC issues
warnings unless it can prove that the use is safe.
https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # on top of v4.19-rc5, clang 7
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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Instead of using version checks per-compiler to define (or not)
each attribute, use __has_attribute to test for them, following
the cleanup started with commit 815f0ddb346c
("include/linux/compiler*.h: make compiler-*.h mutually exclusive"),
which is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
In the meantime, to support 4.6 <= gcc < 5, we implement
__has_attribute by hand.
All the attributes that can be unconditionally defined and directly
map to compiler attribute(s) (even if optional) have been moved
to a new file include/linux/compiler_attributes.h
In an effort to make the file as regular as possible, comments
stating the purpose of attributes have been removed. Instead,
links to the compiler docs have been added (i.e. to gcc and,
if available, to clang as well). In addition, they have been sorted.
Finally, if an attribute is optional (i.e. if it is guarded
by __has_attribute), the reason has been stated for future reference.
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # on top of v4.19-rc5, clang 7
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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