--- /dev/null
+From foo@baz Mon Dec 14 04:48:16 PM CET 2020
+From: Arvind Sankar <nivedita@alum.mit.edu>
+Date: Fri, 13 Nov 2020 22:51:59 -0800
+Subject: compiler.h: fix barrier_data() on clang
+
+From: Arvind Sankar <nivedita@alum.mit.edu>
+
+commit 3347acc6fcd4ee71ad18a9ff9d9dac176b517329 upstream.
+
+Commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
+mutually exclusive") neglected to copy barrier_data() from
+compiler-gcc.h into compiler-clang.h.
+
+The definition in compiler-gcc.h was really to work around clang's more
+aggressive optimization, so this broke barrier_data() on clang, and
+consequently memzero_explicit() as well.
+
+For example, this results in at least the memzero_explicit() call in
+lib/crypto/sha256.c:sha256_transform() being optimized away by clang.
+
+Fix this by moving the definition of barrier_data() into compiler.h.
+
+Also move the gcc/clang definition of barrier() into compiler.h,
+__memory_barrier() is icc-specific (and barrier() is already defined
+using it in compiler-intel.h) and doesn't belong in compiler.h.
+
+[rdunlap@infradead.org: fix ALPHA builds when SMP is not enabled]
+
+Link: https://lkml.kernel.org/r/20201101231835.4589-1-rdunlap@infradead.org
+Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
+Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
+Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Tested-by: Nick Desaulniers <ndesaulniers@google.com>
+Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
+Reviewed-by: Kees Cook <keescook@chromium.org>
+Cc: <stable@vger.kernel.org>
+Link: https://lkml.kernel.org/r/20201014212631.207844-1-nivedita@alum.mit.edu
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+[nd: backport to account for missing
+ commit e506ea451254a ("compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h")
+ commit d08b9f0ca6605 ("scs: Add support for Clang's Shadow Call Stack (SCS)")]
+Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ include/linux/compiler-clang.h | 6 ------
+ include/linux/compiler-gcc.h | 19 -------------------
+ include/linux/compiler.h | 18 ++++++++++++++++--
+ 3 files changed, 16 insertions(+), 27 deletions(-)
+
+--- a/include/linux/compiler-clang.h
++++ b/include/linux/compiler-clang.h
+@@ -36,9 +36,3 @@
+ __has_builtin(__builtin_sub_overflow)
+ #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
+ #endif
+-
+-/* The following are for compatibility with GCC, from compiler-gcc.h,
+- * and may be redefined here because they should not be shared with other
+- * compilers, like ICC.
+- */
+-#define barrier() __asm__ __volatile__("" : : : "memory")
+--- a/include/linux/compiler-gcc.h
++++ b/include/linux/compiler-gcc.h
+@@ -14,25 +14,6 @@
+ # error Sorry, your compiler is too old - please upgrade it.
+ #endif
+
+-/* 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 proved 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.
+--- a/include/linux/compiler.h
++++ b/include/linux/compiler.h
+@@ -80,11 +80,25 @@ void ftrace_likely_update(struct ftrace_
+
+ /* Optimization barrier */
+ #ifndef barrier
+-# define barrier() __memory_barrier()
++/* The "volatile" is due to gcc bugs */
++# define barrier() __asm__ __volatile__("": : :"memory")
+ #endif
+
+ #ifndef barrier_data
+-# define barrier_data(ptr) barrier()
++/*
++ * 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 proved 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")
+ #endif
+
+ /* workaround for GCC PR82365 if needed */
projects / thirdparty / kernel / stable-queue.git / commitdiff
