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.
