Merge pull request #7808 from daverodgman/fix-ct-compile-warning
Fix for arm64_32 (aka ILP32) on Clang
diff --git a/ChangeLog.d/fix-ilp32.txt b/ChangeLog.d/fix-ilp32.txt
new file mode 100644
index 0000000..3f18ac5
--- /dev/null
+++ b/ChangeLog.d/fix-ilp32.txt
@@ -0,0 +1,4 @@
+Bugfix
+ * Fix a compilation failure in the constant_time module when
+ building for arm64_32 (e.g., for watchos). Reported by Paulo
+ Coutinho in #7787.
diff --git a/library/bn_mul.h b/library/bn_mul.h
index c5994f7..43dd5c2 100644
--- a/library/bn_mul.h
+++ b/library/bn_mul.h
@@ -248,27 +248,39 @@
#endif /* AMD64 */
-#if defined(__aarch64__)
+// The following assembly code assumes that a pointer will fit in a 64-bit register
+// (including ILP32 __aarch64__ ABIs such as on watchOS, hence the 2^32 - 1)
+#if defined(__aarch64__) && (UINTPTR_MAX == 0xfffffffful || UINTPTR_MAX == 0xfffffffffffffffful)
+/*
+ * There are some issues around different compilers requiring different constraint
+ * syntax for updating pointers from assembly code (see notes for
+ * MBEDTLS_ASM_AARCH64_PTR_CONSTRAINT in common.h), especially on aarch64_32 (aka ILP32).
+ *
+ * For this reason we cast the pointers to/from uintptr_t here.
+ */
#define MULADDC_X1_INIT \
- asm(
+ do { uintptr_t muladdc_d = (uintptr_t) d, muladdc_s = (uintptr_t) s; asm(
#define MULADDC_X1_CORE \
- "ldr x4, [%2], #8 \n\t" \
- "ldr x5, [%1] \n\t" \
+ "ldr x4, [%x2], #8 \n\t" \
+ "ldr x5, [%x1] \n\t" \
"mul x6, x4, %4 \n\t" \
"umulh x7, x4, %4 \n\t" \
"adds x5, x5, x6 \n\t" \
"adc x7, x7, xzr \n\t" \
"adds x5, x5, %0 \n\t" \
"adc %0, x7, xzr \n\t" \
- "str x5, [%1], #8 \n\t"
+ "str x5, [%x1], #8 \n\t"
#define MULADDC_X1_STOP \
- : "+r" (c), "+r" (d), "+r" (s), "+m" (*(uint64_t (*)[16]) d) \
+ : "+r" (c), \
+ "+r" (muladdc_d), \
+ "+r" (muladdc_s), \
+ "+m" (*(uint64_t (*)[16]) d) \
: "r" (b), "m" (*(const uint64_t (*)[16]) s) \
: "x4", "x5", "x6", "x7", "cc" \
- );
+ ); d = (mbedtls_mpi_uint *)muladdc_d; s = (mbedtls_mpi_uint *)muladdc_s; } while (0);
#endif /* Aarch64 */
diff --git a/library/common.h b/library/common.h
index b48a1fc..ba9cb75 100644
--- a/library/common.h
+++ b/library/common.h
@@ -169,6 +169,27 @@
#endif
/* *INDENT-ON* */
+/*
+ * Define the constraint used for pointer operands to asm.
+ *
+ * This is normally the usual "r", but for aarch64_32 (aka ILP32,
+ * as found in watchos), "p" is required to avoid warnings from clang.
+ *
+ * Note that clang does not recognise '+p' or '=p', and armclang
+ * does not recognise 'p' at all.
+ */
+#if defined(__aarch64__) && defined(MBEDTLS_HAVE_ASM)
+#if UINTPTR_MAX == 0xfffffffful
+/* ILP32: Specify the pointer operand slightly differently, as per #7787. */
+#define MBEDTLS_ASM_AARCH64_PTR_CONSTRAINT "p"
+#elif UINTPTR_MAX == 0xfffffffffffffffful
+/* Normal case (64-bit pointers): use "r" as the constraint for pointer operands to asm */
+#define MBEDTLS_ASM_AARCH64_PTR_CONSTRAINT "r"
+#else
+#error Unrecognised pointer size for aarch64
+#endif
+#endif
+
/* Always provide a static assert macro, so it can be used unconditionally.
* It will expand to nothing on some systems.
* Can be used outside functions (but don't add a trailing ';' in that case:
diff --git a/library/constant_time.c b/library/constant_time.c
index c823b78..2faba69 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -63,7 +63,9 @@
* only used here.
*/
#if defined(MBEDTLS_EFFICIENT_UNALIGNED_ACCESS) && defined(MBEDTLS_HAVE_ASM)
-#if defined(__arm__) || defined(__thumb__) || defined(__thumb2__) || defined(__aarch64__)
+#if ((defined(__arm__) || defined(__thumb__) || defined(__thumb2__)) && \
+ (UINTPTR_MAX == 0xfffffffful)) || defined(__aarch64__)
+/* We check pointer sizes to avoid issues with them not matching register size requirements */
#define MBEDTLS_EFFICIENT_UNALIGNED_VOLATILE_ACCESS
#endif
#endif
@@ -79,7 +81,7 @@
#if defined(__arm__) || defined(__thumb__) || defined(__thumb2__)
asm volatile ("ldr %0, [%1]" : "=r" (r) : "r" (p) :);
#elif defined(__aarch64__)
- asm volatile ("ldr %w0, [%1]" : "=r" (r) : "r" (p) :);
+ asm volatile ("ldr %w0, [%1]" : "=r" (r) : MBEDTLS_ASM_AARCH64_PTR_CONSTRAINT(p) :);
#endif
return r;
}