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File ipxe.646feec4be6a8d3596e3b486747934a8cc481d78.patch of Package xen (Revision d7e2065207477c182d63b0927bfebf46)

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From: Michael Brown <mcb30@ipxe.org>
Date: Thu, 3 Jun 2021 13:34:14 +0100
Subject: 646feec4be6a8d3596e3b486747934a8cc481d78

[crypto] Add memory output constraints for big-integer inline assembly

The ARM versions of the big-integer inline assembly functions include
constraints to indicate that the output value is modified by the
assembly code.  These constraints are not present in the equivalent
code for the x86 versions.

As of GCC 11, this results in the compiler reporting that the output
values may be uninitialized.

Fix by including the relevant memory output constraints.

Reported-by: Christian Hesse <mail@eworm.de>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/arch/x86/core/x86_bigint.c     | 11 ++++++-----
 src/arch/x86/include/bits/bigint.h | 54 +++++++++++++++++++++++++++++++++++++-----------------
 2 files changed, 43 insertions(+), 22 deletions(-)

--- a/src/arch/x86/core/x86_bigint.c
+++ b/src/arch/x86/core/x86_bigint.c
@@ -66,30 +66,31 @@ void bigint_multiply_raw ( const uint32_t *multiplicand0,
 		multiplicand_element = multiplicand->element[i];
 		for ( j = 0 ; j < size ; j++ ) {
 			multiplier_element = multiplier->element[j];
 			result_elements = &result->element[ i + j ];
 			/* Perform a single multiply, and add the
 			 * resulting double-element into the result,
 			 * carrying as necessary.  The carry can
 			 * never overflow beyond the end of the
 			 * result, since:
 			 *
 			 *     a < 2^{n}, b < 2^{n} => ab < 2^{2n}
 			 */
-			__asm__ __volatile__ ( "mull %4\n\t"
-					       "addl %%eax, (%5,%2,4)\n\t"
-					       "adcl %%edx, 4(%5,%2,4)\n\t"
+			__asm__ __volatile__ ( "mull %5\n\t"
+					       "addl %%eax, (%6,%2,4)\n\t"
+					       "adcl %%edx, 4(%6,%2,4)\n\t"
 					       "\n1:\n\t"
-					       "adcl $0, 8(%5,%2,4)\n\t"
+					       "adcl $0, 8(%6,%2,4)\n\t"
 					       "inc %2\n\t"
 						       /* Does not affect CF */
 					       "jc 1b\n\t"
 					       : "=&a" ( discard_a ),
 						 "=&d" ( discard_d ),
-						 "=&r" ( index )
+						 "=&r" ( index ),
+						 "+m" ( *result )
 					       : "0" ( multiplicand_element ),
 						 "g" ( multiplier_element ),
 						 "r" ( result_elements ),
 						 "2" ( 0 ) );
 		}
 	}
 }
--- a/src/arch/x86/include/bits/bigint.h
+++ b/src/arch/x86/include/bits/bigint.h
@@ -16,130 +16,142 @@ typedef uint32_t bigint_element_t;
 
 /**
  * Initialise big integer
  *
  * @v value0		Element 0 of big integer to initialise
  * @v size		Number of elements
  * @v data		Raw data
  * @v len		Length of raw data
  */
 static inline __attribute__ (( always_inline )) void
 bigint_init_raw ( uint32_t *value0, unsigned int size,
 		  const void *data, size_t len ) {
-	long pad_len = ( sizeof ( bigint_t ( size ) ) - len );
+	bigint_t ( size ) __attribute__ (( may_alias )) *value =
+		( ( void * ) value0 );
+	long pad_len = ( sizeof ( *value ) - len );
 	void *discard_D;
 	long discard_c;
 
 	/* Copy raw data in reverse order, padding with zeros */
 	__asm__ __volatile__ ( "\n1:\n\t"
-			       "movb -1(%2,%1), %%al\n\t"
+			       "movb -1(%3,%1), %%al\n\t"
 			       "stosb\n\t"
 			       "loop 1b\n\t"
 			       "xorl %%eax, %%eax\n\t"
-			       "mov %3, %1\n\t"
+			       "mov %4, %1\n\t"
 			       "rep stosb\n\t"
-			       : "=&D" ( discard_D ), "=&c" ( discard_c )
+			       : "=&D" ( discard_D ), "=&c" ( discard_c ),
+				 "+m" ( *value )
 			       : "r" ( data ), "g" ( pad_len ), "0" ( value0 ),
 				 "1" ( len )
 			       : "eax" );
 }
 
 /**
  * Add big integers
  *
  * @v addend0		Element 0 of big integer to add
  * @v value0		Element 0 of big integer to be added to
  * @v size		Number of elements
  */
 static inline __attribute__ (( always_inline )) void
 bigint_add_raw ( const uint32_t *addend0, uint32_t *value0,
 		 unsigned int size ) {
+	bigint_t ( size ) __attribute__ (( may_alias )) *value =
+		( ( void * ) value0 );
 	long index;
 	void *discard_S;
 	long discard_c;
 
 	__asm__ __volatile__ ( "xor %0, %0\n\t" /* Zero %0 and clear CF */
 			       "\n1:\n\t"
 			       "lodsl\n\t"
-			       "adcl %%eax, (%3,%0,4)\n\t"
+			       "adcl %%eax, (%4,%0,4)\n\t"
 			       "inc %0\n\t" /* Does not affect CF */
 			       "loop 1b\n\t"
 			       : "=&r" ( index ), "=&S" ( discard_S ),
-				 "=&c" ( discard_c )
+				 "=&c" ( discard_c ), "+m" ( *value )
 			       : "r" ( value0 ), "1" ( addend0 ), "2" ( size )
 			       : "eax" );
 }
 
 /**
  * Subtract big integers
  *
  * @v subtrahend0	Element 0 of big integer to subtract
  * @v value0		Element 0 of big integer to be subtracted from
  * @v size		Number of elements
  */
 static inline __attribute__ (( always_inline )) void
 bigint_subtract_raw ( const uint32_t *subtrahend0, uint32_t *value0,
 		      unsigned int size ) {
+	bigint_t ( size ) __attribute__ (( may_alias )) *value =
+		( ( void * ) value0 );
 	long index;
 	void *discard_S;
 	long discard_c;
 
 	__asm__ __volatile__ ( "xor %0, %0\n\t" /* Zero %0 and clear CF */
 			       "\n1:\n\t"
 			       "lodsl\n\t"
-			       "sbbl %%eax, (%3,%0,4)\n\t"
+			       "sbbl %%eax, (%4,%0,4)\n\t"
 			       "inc %0\n\t" /* Does not affect CF */
 			       "loop 1b\n\t"
 			       : "=&r" ( index ), "=&S" ( discard_S ),
-				 "=&c" ( discard_c )
+				 "=&c" ( discard_c ), "+m" ( *value )
 			       : "r" ( value0 ), "1" ( subtrahend0 ),
 				 "2" ( size )
 			       : "eax" );
 }
 
 /**
  * Rotate big integer left
  *
  * @v value0		Element 0 of big integer
  * @v size		Number of elements
  */
 static inline __attribute__ (( always_inline )) void
 bigint_rol_raw ( uint32_t *value0, unsigned int size ) {
+	bigint_t ( size ) __attribute__ (( may_alias )) *value =
+		( ( void * ) value0 );
 	long index;
 	long discard_c;
 
 	__asm__ __volatile__ ( "xor %0, %0\n\t" /* Zero %0 and clear CF */
 			       "\n1:\n\t"
-			       "rcll $1, (%2,%0,4)\n\t"
+			       "rcll $1, (%3,%0,4)\n\t"
 			       "inc %0\n\t" /* Does not affect CF */
 			       "loop 1b\n\t"
-			       : "=&r" ( index ), "=&c" ( discard_c )
+			       : "=&r" ( index ), "=&c" ( discard_c ),
+				 "+m" ( *value )
 			       : "r" ( value0 ), "1" ( size ) );
 }
 
 /**
  * Rotate big integer right
  *
  * @v value0		Element 0 of big integer
  * @v size		Number of elements
  */
 static inline __attribute__ (( always_inline )) void
 bigint_ror_raw ( uint32_t *value0, unsigned int size ) {
+	bigint_t ( size ) __attribute__ (( may_alias )) *value =
+		( ( void * ) value0 );
 	long discard_c;
 
 	__asm__ __volatile__ ( "clc\n\t"
 			       "\n1:\n\t"
-			       "rcrl $1, -4(%1,%0,4)\n\t"
+			       "rcrl $1, -4(%2,%0,4)\n\t"
 			       "loop 1b\n\t"
-			       : "=&c" ( discard_c )
+			       : "=&c" ( discard_c ), "+m" ( *value )
 			       : "r" ( value0 ), "0" ( size ) );
 }
 
 /**
  * Test if big integer is equal to zero
  *
  * @v value0		Element 0 of big integer
  * @v size		Number of elements
  * @ret is_zero		Big integer is equal to zero
  */
 static inline __attribute__ (( always_inline, pure )) int
 bigint_is_zero_raw ( const uint32_t *value0, unsigned int size ) {
@@ -239,80 +251,88 @@ bigint_max_set_bit_raw ( const uint32_t *value0, unsigned int size ) {
 
 /**
  * Grow big integer
  *
  * @v source0		Element 0 of source big integer
  * @v source_size	Number of elements in source big integer
  * @v dest0		Element 0 of destination big integer
  * @v dest_size		Number of elements in destination big integer
  */
 static inline __attribute__ (( always_inline )) void
 bigint_grow_raw ( const uint32_t *source0, unsigned int source_size,
 		  uint32_t *dest0, unsigned int dest_size ) {
+	bigint_t ( dest_size ) __attribute__ (( may_alias )) *dest =
+		( ( void * ) dest0 );
 	long pad_size = ( dest_size - source_size );
 	void *discard_D;
 	void *discard_S;
 	long discard_c;
 
 	__asm__ __volatile__ ( "rep movsl\n\t"
 			       "xorl %%eax, %%eax\n\t"
-			       "mov %3, %2\n\t"
+			       "mov %4, %2\n\t"
 			       "rep stosl\n\t"
 			       : "=&D" ( discard_D ), "=&S" ( discard_S ),
-				 "=&c" ( discard_c )
+				 "=&c" ( discard_c ), "+m" ( *dest )
 			       : "g" ( pad_size ), "0" ( dest0 ),
 				 "1" ( source0 ), "2" ( source_size )
 			       : "eax" );
 }
 
 /**
  * Shrink big integer
  *
  * @v source0		Element 0 of source big integer
  * @v source_size	Number of elements in source big integer
  * @v dest0		Element 0 of destination big integer
  * @v dest_size		Number of elements in destination big integer
  */
 static inline __attribute__ (( always_inline )) void
 bigint_shrink_raw ( const uint32_t *source0, unsigned int source_size __unused,
 		    uint32_t *dest0, unsigned int dest_size ) {
+	bigint_t ( dest_size ) __attribute__ (( may_alias )) *dest =
+		( ( void * ) dest0 );
 	void *discard_D;
 	void *discard_S;
 	long discard_c;
 
 	__asm__ __volatile__ ( "rep movsl\n\t"
 			       : "=&D" ( discard_D ), "=&S" ( discard_S ),
-				 "=&c" ( discard_c )
+				 "=&c" ( discard_c ), "+m" ( *dest )
 			       : "0" ( dest0 ), "1" ( source0 ),
 				 "2" ( dest_size )
 			       : "eax" );
 }
 
 /**
  * Finalise big integer
  *
  * @v value0		Element 0 of big integer to finalise
  * @v size		Number of elements
  * @v out		Output buffer
  * @v len		Length of output buffer
  */
 static inline __attribute__ (( always_inline )) void
 bigint_done_raw ( const uint32_t *value0, unsigned int size __unused,
 		  void *out, size_t len ) {
+	struct {
+		uint8_t bytes[len];
+	} __attribute__ (( may_alias )) *out_bytes = out;
 	void *discard_D;
 	long discard_c;
 
 	/* Copy raw data in reverse order */
 	__asm__ __volatile__ ( "\n1:\n\t"
-			       "movb -1(%2,%1), %%al\n\t"
+			       "movb -1(%3,%1), %%al\n\t"
 			       "stosb\n\t"
 			       "loop 1b\n\t"
-			       : "=&D" ( discard_D ), "=&c" ( discard_c )
+			       : "=&D" ( discard_D ), "=&c" ( discard_c ),
+				 "+m" ( *out_bytes )
 			       : "r" ( value0 ), "0" ( out ), "1" ( len )
 			       : "eax" );
 }
 
 extern void bigint_multiply_raw ( const uint32_t *multiplicand0,
 				  const uint32_t *multiplier0,
 				  uint32_t *value0, unsigned int size );
 
 #endif /* _BITS_BIGINT_H */

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