Fix unsafe read during final iteration of zsymv_L_sse2.S

kernel/x86_64/zsymv_L_sse2.S

@@ -451,7 +451,6 @@
 #endif
 
 	MOVDDUP(4 * SIZE, A1, a1)
-	MOVDDUP(6 * SIZE, A2, a2)
 
 	movsd	 0 * SIZE(YY), yy1
 	movhpd	 1 * SIZE(YY), yy1
@@ -471,7 +470,9 @@
 	subq	IS, I
 	subq	$2, I
 	sarq	$2, I
-	jle	.L15
+	jle	.L14
+
+	MOVDDUP(6 * SIZE - (4 * SIZE), A2, a2)
 	ALIGN_3
 
 .L12:
@@ -632,6 +633,16 @@
 	jg	 .L12
 	ALIGN_3
 
+.L14:
+	movq     M, I
+	subq    IS, I
+	subq    $2, I
+	testq   $2, I
+	jle     .L16
+
+	MOVDDUP(6 * SIZE - (4 * SIZE), A2, a2)
+	jmp     .L15_pastcheck
+
 .L15:
 	movq	 M, I
 	subq	IS, I
@@ -639,6 +650,7 @@
 	testq	$2, I
 	jle	.L16
 
+.L15_pastcheck:
 	movapd	  xtemp1, xt1
 	mulpd	  a1,     xt1
 	mulpd	  atemp1, a1

test_zhemv.c

@@ -0,0 +1,85 @@
+//  reproduce segfault in zhemv() from zsymv_L_sse2.S
+//
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+#include <string.h>
+#include <complex.h>
+#include <sys/mman.h>
+
+#define CALL_ZHEMV zhemv_
+
+void zhemv_(char *UPLO, int *N, double *alpha, double *A, int *LDA,
+		double *X, int *INCX, double *beta, double *Y, int *INCY);
+
+int main () {
+    
+    // zhemv parameters
+    char uplo = 'L';
+    int n = 14;
+    int lda = 16;
+    int incx = 1;
+    int incy = 1;
+    double *A, *X, *Y;    
+    double alpha[] = {1, 0};
+    double beta[] = {0, 0};
+
+    // other parameters
+    int i, j;
+    double *data, *data_end, *no_access;
+    double real, imag;
+    int size;
+    size_t len;
+    int A_offset;
+
+    size = sizeof(complex double);
+    len = lda * lda * size;
+
+    // allocate memory for data
+    // use mmap address hints to set up inaccessible memory section following data
+    no_access = mmap(NULL, len, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+    data = mmap(no_access, len, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+    data_end = data + (lda * lda * 2);
+    printf("data start/end: %p/%p. Blocked region starts at %p.\n", data, data_end, no_access);
+
+    // set up pointer offsets into data
+    A_offset = (lda + 1) * 2;
+    A = data + A_offset * 2;			// A starts in the third column of data matrix
+    X = data + A_offset + 2;			// X is the second column of data matrix
+    Y = (double *)malloc(n * incy * size);	// Y is stored elsewhere
+    printf("Address of data: %p; A: %p; X: %p; Y: %p.\n", data, A, X, Y);
+
+
+    // hermitian matrix
+    srand(lda);
+    for (j=0; j<lda; j++) {
+        real = (double) rand() / RAND_MAX;
+        imag = 0;
+        data[(j*lda + j) * 2] = real;
+        data[(j*lda + j) * 2 + 1] = imag;
+        for (i=j+1; i<lda; i++) {
+            real = (double) rand() / RAND_MAX;
+            imag = (double) rand() / RAND_MAX;
+            data[(j*lda + i) * 2] = real;
+            data[(j*lda + i) * 2 + 1] = imag;
+            data[(i*lda + j) * 2] = real;
+            data[(i*lda + j) * 2 + 1] = -imag;
+        }
+    }
+
+    for (int i=0; i<incy*n*2; i++) {
+        Y[i] = 0;
+    }
+
+    CALL_ZHEMV(&uplo, &n, alpha, A, &lda, X, &incx, beta, Y, &incy);
+
+    printf("Finished call to zhemv.\n");
+
+    munmap(no_access, len);
+    munmap(data, len);
+
+}
+
+
+