Handle __gmon_start__ as undefined weak or hidden on hppa

The attached change fixes libc/19170.  It is identical to the approach used on ia64 aside from
the hppa assembler code.

It has been build tested on trunk and with Debian 2.19.  It resolves the harfbuzz issue noted in
the PR.

Please install if okay.

Dave
--
John David Anglin	dave.anglin@bell.net
2015-10-25  Helge Deller  <deller@gmx.de>
	    John David Anglin  <danglin@gcc.gnu.org>

	PR libc/19170
	* sysdeps/hppa/crti.S (gmon_initializer): New.  Use .init_array support
	to call gmon_initializer.  Only call __gmon_start__ when symbol is
	defined.
	* sysdeps/hppa/crtn.S (__gmon_start__): Delete.

On 2015-10-25, at 3:32 PM, John David Anglin wrote:

> The attached change fixes libc/19170.  It is identical to the approach used on ia64 aside from
> the hppa assembler code.

I committed the attached change which has been used on Debian for some time.

Dave
--
John David Anglin	dave.anglin@bell.net
2017-12-02  John David Anglin  <danglin@gcc.gnu.org>

	[BZ libc/19170]
	* sysdeps/hppa/crti.S: Declare PREINIT_FUNCTION weak_extern when
	PREINIT_FUNCTION_WEAK is nonzero.
	(gmon_initializer): New function.  Put procedure label for it in
	.init_array section.
	(_init): Don't call PREINIT_FUNCTION.
	* sysdeps/hppa/crtn.S (__gmon_start__): Remove.
	* sysdeps/hppa/dl-lookupcfg.h (DL_FIXUP_MAKE_VALUE): Create null fixup
	value when map argument is null.

diff --git a/sysdeps/hppa/crti.S b/sysdeps/hppa/crti.S
index 7c1470ddf8..0f9bb7b013 100644
--- a/sysdeps/hppa/crti.S
+++ b/sysdeps/hppa/crti.S
@@ -49,6 +49,95 @@
 # define PREINIT_FUNCTION_WEAK 1
 #endif
 
+#if PREINIT_FUNCTION_WEAK
+	weak_extern (PREINIT_FUNCTION)
+#else
+	.hidden PREINIT_FUNCTION
+#endif
+
+
+/* If we have working .init_array support, we want to keep the .init
+   section empty (apart from the mandatory prologue/epilogue.  This
+   ensures that the default unwind conventions (return-pointer in b0,
+   frame state in ar.pfs, etc.)  will do the Right Thing.  To ensure
+   an empty .init section, we register gmon_initializer() via the
+   .init_array.
+
+    --davidm 02/10/29 */
+
+#if PREINIT_FUNCTION_WEAK
+/* This blob of assembly code is one simple C function:
+
+static void
+__attribute__ ((used))
+gmon_initializer (void)
+{
+  extern void weak_function __gmon_start__ (void);
+
+  if (__gmon_start__)
+    (*__gmon_start__)();
+}
+
+In a final executable, PLABEL32 relocations for function pointers are
+resolved at link time.  Typically, binutils/ld resolves __gmon_start__
+using an external shared library.  __gmon_start__ is always called if
+it is found at link time.  If __gmon_start__ is not found at runtime
+due to a library update, then the function pointer will point at a null
+function descriptor and calling it will cause a segmentation fault.
+So, we call __canonicalize_funcptr_for_compare to obtain the canonicalized
+address of __gmon_start__ and skip calling __gmon_start__ if it is zero.
+
+ */
+	.type __canonicalize_funcptr_for_compare,@function
+	.type $$dyncall,@function
+
+	.section .data.rel.ro,"aw",@progbits
+	.align 4
+.LC0:
+	.type __gmon_start__,@function
+	.word P%__gmon_start__
+
+	.text
+	.align 4
+	.type gmon_initializer,@function
+gmon_initializer:
+	.PROC
+	.CALLINFO FRAME=64,CALLS,SAVE_RP,ENTRY_GR=4
+	.ENTRY
+	stw %r2,-20(%r30)
+	stwm %r4,64(%r30)
+	stw %r3,-60(%r30)
+	addil LT'.LC0,%r19
+	ldw RT'.LC0(%r1),%r28
+	ldw 0(%r28),%r3
+	comib,= 0,%r3,1f
+	copy %r19,%r4
+	stw %r19,-32(%r30)
+	bl __canonicalize_funcptr_for_compare,%r2
+	copy %r3,%r26
+	comib,= 0,%r28,1f
+	copy %r4,%r19
+	copy %r3,%r22
+	.CALL ARGW0=GR
+	bl $$dyncall,%r31
+	copy %r31,%r2
+1:
+	ldw -84(%r30),%r2
+	ldw -60(%r30),%r3
+	bv %r0(%r2)
+	ldwm -64(%r30),%r4
+	.EXIT
+	.PROCEND
+	.size gmon_initializer, .-gmon_initializer
+
+# undef PREINIT_FUNCTION
+# define PREINIT_FUNCTION gmon_initializer
+#endif
+
+	.section .init_array, "aw"
+	.word P% PREINIT_FUNCTION
+
+
 /* _init prologue.  */
 	.section .init, "ax", %progbits
 	.align 4
@@ -58,14 +147,6 @@ _init:
 	stw	%rp,-20(%sp)
 	stwm	%r4,64(%sp)
 	stw	%r19,-32(%sp)
-#if PREINIT_FUNCTION_WEAK
-	bl	PREINIT_FUNCTION,%rp
-	copy	%r19,%r4	/* delay slot */
-#else
-	bl	PREINIT_FUNCTION,%rp
-	copy	%r19,%r4	/* delay slot */
-#endif
-	copy	%r4,%r19
 
 /* _fini prologue.  */
         .section .fini,"ax",%progbits
diff --git a/sysdeps/hppa/crtn.S b/sysdeps/hppa/crtn.S
index 42f310d217..49666b81f9 100644
--- a/sysdeps/hppa/crtn.S
+++ b/sysdeps/hppa/crtn.S
@@ -38,27 +38,6 @@
 /* crtn.S puts function epilogues in the .init and .fini sections
    corresponding to the prologues in crti.S. */
 
-/* Note that we cannot have a weak undefined __gmon_start__, because
-   that would require this to be PIC, and the linker is currently not
-   able to generate a proper procedure descriptor for _init.  Sad but
-   true.  Anyway, HPPA is one of those horrible architectures where
-   making the comparison and indirect call is quite expensive (see the
-   comment in sysdeps/generic/initfini.c). */
-        .text
-        .align 4
-        .weak   __gmon_start__
-        .type    __gmon_start__,@function
-__gmon_start__:
-	.proc
-	.callinfo
-	.entry
-        bv,n %r0(%r2)
-	.exit
-	.procend
-
-/* Here is the tail end of _init.  We put __gmon_start before this so
-   that the assembler creates the .PARISC.unwind section for us, ie.
-   with the right attributes.  */
 	.section .init, "ax", @progbits
 	ldw	-84(%sp),%rp
 	copy	%r4,%r19
diff --git a/sysdeps/hppa/dl-lookupcfg.h b/sysdeps/hppa/dl-lookupcfg.h
index 0b0ae85b5d..0b8f031823 100644
--- a/sysdeps/hppa/dl-lookupcfg.h
+++ b/sysdeps/hppa/dl-lookupcfg.h
@@ -73,7 +73,8 @@ void attribute_hidden _dl_unmap (struct link_map *map);
 
 /* Construct a fixup value from the address and linkmap */
 #define DL_FIXUP_MAKE_VALUE(map, addr) \
-   ((struct fdesc) { (addr), (map)->l_info[DT_PLTGOT]->d_un.d_ptr })
+  (map) ? ((struct fdesc) { (addr), (map)->l_info[DT_PLTGOT]->d_un.d_ptr }) \
+	: ((struct fdesc) { 0, 0 })
 
 /* Extract the code address from a fixup value */
 #define DL_FIXUP_VALUE_CODE_ADDR(value) ((value).ip)