ia64: Don't inherit all PSR bits across fork() & exec().

arch/ia64/kernel/process.c

@@ -325,6 +325,11 @@ copy_thread (int nr, unsigned long clone_flags,
 
 	/* copy parts of thread_struct: */
 	p->thread.ksp = (unsigned long) child_stack - 16;
+
+	/* stop some PSR bits from being inherited: */
+	child_ptregs->cr_ipsr =  ((child_ptregs->cr_ipsr | IA64_PSR_BITS_TO_SET)
+				  & ~IA64_PSR_BITS_TO_CLEAR);
+
 	/*
 	 * NOTE: The calling convention considers all floating point
 	 * registers in the high partition (fph) to be scratch.  Since

include/asm-ia64/kregs.h

@@ -64,6 +64,15 @@
 #define IA64_PSR_RI_BIT		41
 #define IA64_PSR_ED_BIT		43
 #define IA64_PSR_BN_BIT		44
+#define IA64_PSR_IA	(__IA64_UL(1) << IA64_PSR_IA_BIT)
+
+/* A mask of PSR bits that we generally don't want to inherit across a clone2() or an
+   execve().  Only list flags here that need to be cleared/set for BOTH clone2() and
+   execve().  */
+#define IA64_PSR_BITS_TO_CLEAR	(IA64_PSR_MFL | IA64_PSR_MFH | IA64_PSR_DB | IA64_PSR_LP | \
+				 IA64_PSR_TB  | IA64_PSR_ID  | IA64_PSR_DA | IA64_PSR_DD | \
+				 IA64_PSR_SS  | IA64_PSR_ED  | IA64_PSR_IA)
+#define IA64_PSR_BITS_TO_SET	(IA64_PSR_DFH)
 
 #define IA64_PSR_BE	(__IA64_UL(1) << IA64_PSR_BE_BIT)
 #define IA64_PSR_UP	(__IA64_UL(1) << IA64_PSR_UP_BIT)

include/asm-ia64/processor.h

@@ -270,12 +270,8 @@ struct thread_struct {
 
 #define start_thread(regs,new_ip,new_sp) do {							\
 	set_fs(USER_DS);									\
-	ia64_psr(regs)->dfh = 1;	/* disable fph */					\
-	ia64_psr(regs)->mfh = 0;	/* clear mfh */						\
-	ia64_psr(regs)->cpl = 3;	/* set user mode */					\
-	ia64_psr(regs)->ri = 0;		/* clear return slot number */				\
-	ia64_psr(regs)->is = 0;		/* IA-64 instruction set */				\
-	ia64_psr(regs)->sp = 1;		/* enforce secure perfmon */				\
+	regs->cr_ipsr = ((regs->cr_ipsr | (IA64_PSR_BITS_TO_SET | IA64_PSR_CPL | IA64_PSR_SP))	\
+			 & ~(IA64_PSR_BITS_TO_CLEAR | IA64_PSR_RI | IA64_PSR_IS));		\
 	regs->cr_iip = new_ip;									\
 	regs->ar_rsc = 0xf;		/* eager mode, privilege level 3 */			\
 	regs->ar_rnat = 0;									\