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authorArvind Sankar <nivedita@alum.mit.edu>2019-10-07 18:00:02 -0400
committerIngo Molnar <mingo@kernel.org>2019-10-08 13:27:05 +0200
commitbec500777089b3c96c53681fc0aa6fee59711d4a (patch)
tree6e18458897b6246afc04242d3e38dcaf032e366c /include/linux/string.h
parentfbcfb8f0270bf24fe348393540b17a7f2ba577d7 (diff)
lib/string: Make memzero_explicit() inline instead of external
With the use of the barrier implied by barrier_data(), there is no need for memzero_explicit() to be extern. Making it inline saves the overhead of a function call, and allows the code to be reused in arch/*/purgatory without having to duplicate the implementation. Tested-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> Reviewed-by: Hans de Goede <hdegoede@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Borislav Petkov <bp@alien8.de> Cc: H . Peter Anvin <hpa@zytor.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephan Mueller <smueller@chronox.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-crypto@vger.kernel.org Cc: linux-s390@vger.kernel.org Fixes: 906a4bb97f5d ("crypto: sha256 - Use get/put_unaligned_be32 to get input, memzero_explicit") Link: https://lkml.kernel.org/r/20191007220000.GA408752@rani.riverdale.lan Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/string.h')
-rw-r--r--include/linux/string.h21
1 files changed, 20 insertions, 1 deletions
diff --git a/include/linux/string.h b/include/linux/string.h
index b2f9df7f0761..b6ccdc2c7f02 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -227,7 +227,26 @@ static inline bool strstarts(const char *str, const char *prefix)
}
size_t memweight(const void *ptr, size_t bytes);
-void memzero_explicit(void *s, size_t count);
+
+/**
+ * memzero_explicit - Fill a region of memory (e.g. sensitive
+ * keying data) with 0s.
+ * @s: Pointer to the start of the area.
+ * @count: The size of the area.
+ *
+ * Note: usually using memset() is just fine (!), but in cases
+ * where clearing out _local_ data at the end of a scope is
+ * necessary, memzero_explicit() should be used instead in
+ * order to prevent the compiler from optimising away zeroing.
+ *
+ * memzero_explicit() doesn't need an arch-specific version as
+ * it just invokes the one of memset() implicitly.
+ */
+static inline void memzero_explicit(void *s, size_t count)
+{
+ memset(s, 0, count);
+ barrier_data(s);
+}
/**
* kbasename - return the last part of a pathname.