commit 6e22494e5076e4d3c0b2c2785883162f83db499e Author: Jan Kratochvil 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 * 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 * 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, + ¤t_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 . */ + + .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 . + +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 .*"