commit 02e17c0aa59f1146b9a566e672940ffdca75a2a2
author Gilles Peskine <gilles.peskine@arm.com> Mon Sep 20 22:23:53 2021 +0200
committer GitHub <noreply@github.com> Mon Sep 20 22:23:53 2021 +0200
tree 51cf3bd44a7547047de4c458f7c5a762bda9ef7f
parent 3c0f30484874d857a5008bb6b9626ccdbab22110
parent 184a688d516a2532413ffbf48b5140ed0674d026

Merge pull request #4941 from gilles-peskine-arm/muladdc-amd64-memory-2.x

Backport 2.x: Fix x86_64 assembly for bignum multiplication

ChangeLog.d/muladdc-amd64-memory.txt

diff --git a/ChangeLog.d/muladdc-amd64-memory.txt b/ChangeLog.d/muladdc-amd64-memory.txt
new file mode 100644
index 0000000..b834331
--- /dev/null
+++ b/ChangeLog.d/muladdc-amd64-memory.txt
@@ -0,0 +1,4 @@
+Bugfix
+   * Fix missing constraints on x86_64 assembly code for bignum multiplication
+     that broke some bignum operations with (at least) Clang 12.
+     Fixes #4116, #4786, #4917.

include/mbedtls/bn_mul.h

diff --git a/include/mbedtls/bn_mul.h b/include/mbedtls/bn_mul.h
index a0fa677..716bd3b 100644
--- a/include/mbedtls/bn_mul.h
+++ b/include/mbedtls/bn_mul.h
@@ -229,9 +229,9 @@
         "addq   $8, %%rdi\n"
 
 #define MULADDC_STOP                        \
-        : "+c" (c), "+D" (d), "+S" (s)      \
-        : "b" (b)                           \
-        : "rax", "rdx", "r8"                \
+        : "+c" (c), "+D" (d), "+S" (s), "+m" (*(uint64_t (*)[16]) d) \
+        : "b" (b), "m" (*(const uint64_t (*)[16]) s)                 \
+        : "rax", "rdx", "r8"                                         \
     );
 
 #endif /* AMD64 */