[RS6000] libgcc cfi

There are a few places in libgcc assembly where we don't emit call
frame information for functions, potentially breaking unwinding from
asynchronous signal handlers.  This patch fixes them.  Although I
patch tramp.S there is no attempt made to provide CFI for the actual
trampoline on the stack.  Doing that would require generating CFI at
run time and both registering and deregistering it, which is probably
not worth doing since it would significantly slow down the call.

	* config/rs6000/morestack.S (__stack_split_initialize),
	(__morestack_get_guard, __morestack_set_guard),
	(__morestack_make_guard): Provide CFI covering these functions.
	* config/rs6000/tramp.S (__trampoline_setup): Likewise.

From-SVN: r266503

libgcc/ChangeLog

+2018-11-27  Alan Modra  <amodra@gmail.com>
+
+	* config/rs6000/morestack.S (__stack_split_initialize),
+	(__morestack_get_guard, __morestack_set_guard),
+	(__morestack_make_guard): Provide CFI covering these functions.
+	* config/rs6000/tramp.S (__trampoline_setup): Likewise.
+
 2018-11-15  Xianmiao Qu  <xianmiao_qu@c-sky.com>
 
 	* config/csky/linux-unwind.h (sc_pt_regs): Update for kernel.

libgcc/config/rs6000/morestack.S

@@ -304,12 +304,15 @@ DW.ref.__gcc_personality_v0:
 # new thread starts.  This is called from a constructor.
 # void __stack_split_initialize (void)
 ENTRY(__stack_split_initialize)
+	.cfi_startproc
 	addi %r3,%r1,-0x4000		# We should have at least 16K.
 	std %r3,-0x7000-64(%r13)	# tcbhead_t.__private_ss
 	# void __generic_morestack_set_initial_sp (void *sp, size_t len)
 	mr %r3,%r1
 	li %r4, 0x4000
 	b __generic_morestack_set_initial_sp
+# The lack of .cfi_endproc here is deliberate.  This function and the
+# following ones can all use the default FDE.
 	SIZE (__stack_split_initialize)
 
 
@@ -335,6 +338,7 @@ ENTRY0(__morestack_make_guard)
 	sub %r3,%r3,%r4
 	addi %r3,%r3,BACKOFF
 	blr
+	.cfi_endproc
 	SIZE (__morestack_make_guard)
 
 

libgcc/config/rs6000/tramp.S

@@ -56,8 +56,10 @@ trampoline_size = .-trampoline_initial
 /* R6 = static chain */
 
 FUNC_START(__trampoline_setup)
+	.cfi_startproc
 	mflr	r0		/* save return address */
         bcl	20,31,.LCF0	/* load up __trampoline_initial into r7 */
+	.cfi_register lr,r0
 .LCF0:
         mflr	r11
         addi	r7,r11,trampoline_initial-4-.LCF0 /* trampoline address -4 */
@@ -112,6 +114,7 @@ FUNC_START(__trampoline_setup)
 	addi	r30,r30,_GLOBAL_OFFSET_TABLE_-1b@l
 #endif
 	bl	JUMP_TARGET(abort)
+	.cfi_endproc
 FUNC_END(__trampoline_setup)
 
 #endif
@@ -144,6 +147,7 @@ trampoline_size = .-trampoline_initial
 	.popsection
 
 FUNC_START(__trampoline_setup)
+	.cfi_startproc
 	addis 7,2,.LC0@toc@ha
 	ld 7,.LC0@toc@l(7)	/* trampoline address -8 */
 
@@ -180,6 +184,7 @@ FUNC_START(__trampoline_setup)
 .Labort:
 	bl	JUMP_TARGET(abort)
 	nop
+	.cfi_endproc
 FUNC_END(__trampoline_setup)
 
 #endif