powerpc64: fix 64-bit process detection on embedded

* syscall.c (get_scno) [POWERPC64]: Fix 64-bit process detection
on embedded powerpc.

Upstream-Status: Backport

Signed-off-by: James Yang <james.yang@freescale.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>

diff --git a/syscall.c.orig b/syscall.c
index 7efee0e..72d9453 100644
--- a/syscall.c.orig
+++ b/syscall.c
@@ -1207,11 +1207,14 @@ get_scno(struct tcb *tcp)
 	/* Check for 64/32 bit mode. */
 	if (upeek(tcp, sizeof(unsigned long)*PT_MSR, &val) < 0)
 		return -1;
-	/* SF is bit 0 of MSR */
-	if (val < 0)
-		currpers = 0;
-	else
-		currpers = 1;
+
+	/*
+	 * Check for 64/32 bit mode.
+	 * Embedded implementations covered by Book E extension of PPC use
+	 * bit 0 (CM) of 32-bit Machine state register (MSR).
+	 * Other implementations use bit 0 (SF) of 64-bit MSR.
+	 */
+	currpers = (val & 0x8000000080000000) ? 0 : 1;
 	update_personality(tcp, currpers);
 # endif
 #elif defined(AVR32)