commit 6e22494e5076e4d3c0b2c2785883162f83db499e

Author: Jan Kratochvil <jan.kratochvil@redhat.com>

Date:   Fri Jun 26 15:11:14 2015 +0200

    Do not skip prologue for asm (.S) files

    GDB tries to skip prologue for .S files according to .debug_line but it then

    places the breakpoint to a location where it is never hit.

    This is because #defines in .S files cause prologue skipping which is

    completely inappropriate, for s390x:

    glibc/sysdeps/unix/syscall-template.S

    78:/* This is a "normal" system call stub: if there is an error,

    79:   it returns -1 and sets errno.  */

    80:

    81:T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)

    82:     ret

    00000000000f4210 T __select

     Line Number Statements:

      Extended opcode 2: set Address to 0xf41c8

      Advance Line by 80 to 81

      Copy

      Advance PC by 102 to 0xf422e

      Special opcode 6: advance Address by 0 to 0xf422e and Line by 1 to 82

      Special opcode 34: advance Address by 2 to 0xf4230 and Line by 1 to 83

      Advance PC by 38 to 0xf4256

      Extended opcode 1: End of Sequence

      Compilation Unit @ offset 0x28b3e0:

     <0><28b3eb>: Abbrev Number: 1 (DW_TAG_compile_unit)

        <28b3ec>   DW_AT_stmt_list   : 0x7b439

        <28b3f0>   DW_AT_low_pc	 : 0xf41c8

        <28b3f8>   DW_AT_high_pc     : 0xf4256

        <28b400>   DW_AT_name        : ../sysdeps/unix/syscall-template.S

        <28b423>   DW_AT_comp_dir    : /usr/src/debug////////glibc-2.17-c758a686/misc

        <28b452>   DW_AT_producer    : GNU AS 2.23.52.0.1

        <28b465>   DW_AT_language    : 32769        (MIPS assembler)

    without debuginfo or with debuginfo and the fix - correct address:

    (gdb) b select

    Breakpoint 1 at 0xf4210

    It is also where .dynsym+.symtab point to:

    00000000000f4210 T __select

    00000000000f4210 W select

    with debuginfo, without the fix:

    (gdb) b select

    Breakpoint 1 at 0xf41c8: file ../sysdeps/unix/syscall-template.S, line 81.

    One part is to behave for asm files similar way like for 'locations_valid':

      /* Symtab has been compiled with both optimizations and debug info so that

         GDB may stop skipping prologues as variables locations are valid already

         at function entry points.  */

      unsigned int locations_valid : 1;

    The other part is to extend the 'locations_valid'-like functionality more.

    Both minsym_found and find_function_start_sal need to be patched, otherwise

    their addresses do not match and GDB regresses on ppc64:

    gdb/ChangeLog

    2015-06-26  Jan Kratochvil  <jan.kratochvil@redhat.com>

    	* linespec.c (minsym_found): Reset sal.PC for COMPUNIT_LOCATIONS_VALID

    	and language_asm..

    	* symtab.c (find_function_start_sal): Likewise.

    gdb/testsuite/ChangeLog

    2015-06-26  Jan Kratochvil  <jan.kratochvil@redhat.com>

    	* gdb.arch/amd64-prologue-skip.S: New file.

    	* gdb.arch/amd64-prologue-skip.exp: New file.

Index: gdb-7.6.1/gdb/linespec.c

===================================================================

--- gdb-7.6.1.orig/gdb/linespec.c

+++ gdb-7.6.1/gdb/linespec.c

@@ -3386,7 +3386,9 @@ collect_symbols (struct symbol *sym, voi

 }

 /* We've found a minimal symbol MSYMBOL in OBJFILE to associate with our

-   linespec; return the SAL in RESULT.  */

+   linespec; return the SAL in RESULT.  This function should return SALs

+   matching those from find_function_start_sal, otherwise false

+   multiple-locations breakpoints could be placed.  */

 static void

 minsym_found (struct linespec_state *self, struct objfile *objfile,

@@ -3408,7 +3410,23 @@ minsym_found (struct linespec_state *sel

     sal = find_pc_sect_line (pc, NULL, 0);

   if (self->funfirstline)

-    skip_prologue_sal (&sal;;

+    {

+      if (sal.symtab != NULL

+	  && (sal.symtab->locations_valid

+	      || sal.symtab->language == language_asm))

+	{

+	  /* If gdbarch_convert_from_func_ptr_addr does not apply then

+	     sal.SECTION, sal.LINE&co. will stay correct from above.

+	     If gdbarch_convert_from_func_ptr_addr applies then

+	     sal.SECTION is cleared from above and sal.LINE&co. will

+	     stay correct from the last find_pc_sect_line above.  */

+	  sal.pc = SYMBOL_VALUE_ADDRESS (msymbol);

+	  sal.pc = gdbarch_convert_from_func_ptr_addr (gdbarch, sal.pc,

+						       &current_target);

+	}

+      else

+	skip_prologue_sal (&sal;;

+    }

   if (maybe_add_address (self->addr_set, objfile->pspace, sal.pc))

     add_sal_to_sals (self, result, &sal, SYMBOL_NATURAL_NAME (msymbol), 0);

Index: gdb-7.6.1/gdb/symtab.c

===================================================================

--- gdb-7.6.1.orig/gdb/symtab.c

+++ gdb-7.6.1/gdb/symtab.c

@@ -2762,7 +2762,9 @@ skip_prologue_using_lineinfo (CORE_ADDR

 /* Given a function symbol SYM, find the symtab and line for the start

    of the function.

    If the argument FUNFIRSTLINE is nonzero, we want the first line

-   of real code inside the function.  */

+   of real code inside the function.

+   This function should return SALs matching those from minsym_found,

+   otherwise false multiple-locations breakpoints could be placed.  */

 struct symtab_and_line

 find_function_start_sal (struct symbol *sym, int funfirstline)

@@ -2773,6 +2775,14 @@ find_function_start_sal (struct symbol *

   sal = find_pc_sect_line (BLOCK_START (SYMBOL_BLOCK_VALUE (sym)),

 			   SYMBOL_OBJ_SECTION (sym), 0);

+  if (funfirstline && sal.symtab != NULL

+      && (sal.symtab->locations_valid

+	  || sal.symtab->language == language_asm))

+    {

+      sal.pc = BLOCK_START (SYMBOL_BLOCK_VALUE (sym));

+      return sal;

+    }

+

   /* We always should have a line for the function start address.

      If we don't, something is odd.  Create a plain SAL refering

      just the PC and hope that skip_prologue_sal (if requested)

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/amd64-prologue-skip.S

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/amd64-prologue-skip.S

@@ -0,0 +1,28 @@

+/* This testcase is part of GDB, the GNU debugger.

+

+   Copyright 2015 Free Software Foundation, Inc.

+

+   This program is free software; you can redistribute it and/or modify

+   it under the terms of the GNU General Public License as published by

+   the Free Software Foundation; either version 3 of the License, or

+   (at your option) any later version.

+

+   This program is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+   GNU General Public License for more details.

+

+   You should have received a copy of the GNU General Public License

+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

+

+	.text

+/*0*/	hlt

+pushrbp: .globl pushrbp

+#define PUSHRBP push %rbp; mov %rsp, %rbp; nop

+/*1*/	PUSHRBP

+/*6*/	hlt

+

+/*7*/	hlt

+#define MINSYM nop; .globl minsym; minsym: nop

+/*8*/	MINSYM

+/*a*/	hlt

Index: gdb-7.6.1/gdb/testsuite/gdb.arch/amd64-prologue-skip.exp

===================================================================

--- /dev/null

+++ gdb-7.6.1/gdb/testsuite/gdb.arch/amd64-prologue-skip.exp

@@ -0,0 +1,35 @@

+# Copyright 2010-2015 Free Software Foundation, Inc.

+

+# This program is free software; you can redistribute it and/or modify

+# it under the terms of the GNU General Public License as published by

+# the Free Software Foundation; either version 3 of the License, or

+# (at your option) any later version.

+#

+# This program is distributed in the hope that it will be useful,

+# but WITHOUT ANY WARRANTY; without even the implied warranty of

+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+# GNU General Public License for more details.

+#

+# You should have received a copy of the GNU General Public License

+# along with this program.  If not, see <http://www.gnu.org/licenses/>.

+

+standard_testfile .S

+set binfile ${binfile}.o

+

+if { ![istarget x86_64-*-* ] || ![is_lp64_target] } {

+    verbose "Skipping ${testfile}."

+    return

+}

+

+if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" object {debug}] != "" } {

+    untested ${testfile}

+    return

+}

+

+clean_restart ${binfile}

+

+gdb_test "break *pushrbp" " at 0x1: file .*"

+gdb_test "break pushrbp" " at 0x1: file .*"

+

+gdb_test "break *minsym" " at 0x9: file .*"

+gdb_test "break minsym" " at 0x9: file .*"