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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 .*"