[gdb/symtab] Trust epilogue unwind info for unknown producer (-g0 case)

For a -g0 -fasynchronous-unwind-tables exec (without .debug_info but with
.eh_frame section), start using the dwarf2 unwinder instead of the
"amd64 epilogue override" unwinder, by returning true in
compunit_epilogue_unwind_valid for cust == nullptr.

This has effect both on the amd64 and i386 targets, but only add amd64
test-case gdb.base/unwind-on-each-insn-amd64-2.exp.

diff --git a/gdb/symtab.h b/gdb/symtab.h
index cd6b5f722fd8670d157426ef2bc76039d7b64978..17d2746fd48fc2534fe98f4494b13e3cb667ca3e 100644 (file)
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -1924,9 +1924,9 @@ static inline bool
 compunit_epilogue_unwind_valid (struct compunit_symtab *cust)
 {
   /* In absence of producer information, assume epilogue unwind info is
-     invalid.  */
+     valid.  */
   if (cust == nullptr)
-    return false;
+    return true;
 
   return cust->epilogue_unwind_valid ();
 }

diff --git a/gdb/testsuite/gdb.base/unwind-on-each-insn-amd64-2.exp b/gdb/testsuite/gdb.base/unwind-on-each-insn-amd64-2.exp
new file mode 100644 (file)
index 0000000..c8a94cc
--- /dev/null
+++ b/gdb/testsuite/gdb.base/unwind-on-each-insn-amd64-2.exp
@@ -0,0 +1,52 @@
+# Copyright 2023 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/>.  */
+
+# Check that epilogue unwind info is used, even if no debug info is available.
+
+require is_x86_64_m64_target
+
+set srcfile_flags {debug}
+set srcfile2_flags {nodebug}
+
+if [info exists COMPILE] {
+    # Make sure that we use .eh_frame info, by generating it
+    # using -fasynchronous-unwind-tables.
+    if { [gdb_can_simple_compile fasynchronous-unwind-tables \
+             { void foo () { } } object -fasynchronous-unwind-tables] } {
+       lappend srcfile2_flags additional_flags=-fasynchronous-unwind-tables
+    } else {
+       unsupported "required: .eh_frame"
+       return
+    }
+    standard_testfile unwind-on-each-insn.c unwind-on-each-insn-foo.c
+    # When updating the .s file, use these flags to generate the file:
+    #lappend srcfile2_flags additional_flags=-save-temps
+    #lappend srcfile2_flags additional_flags=-dA
+    # and do the following:
+    # - copy it in place, run the test-case and verify that all tests pass.
+    # - confuse the amd64 epilogue unwinder by inserting the following
+    #   in foo:
+    #          nop
+    #     +    pushq $.L1
+    #     +    ret
+    #     +  .L1:
+    #     +    nop
+    #          popq %rbp
+    # - verify that the test-case passes.
+} else {
+    standard_testfile unwind-on-each-insn.c .s
+}
+
+source $srcdir/$subdir/unwind-on-each-insn.exp.tcl

diff --git a/gdb/testsuite/gdb.base/unwind-on-each-insn-amd64-2.s b/gdb/testsuite/gdb.base/unwind-on-each-insn-amd64-2.s
new file mode 100644 (file)
index 0000000..c141f71
--- /dev/null
+++ b/gdb/testsuite/gdb.base/unwind-on-each-insn-amd64-2.s
@@ -0,0 +1,54 @@
+       .file   "unwind-on-each-insn-foo.c"
+       .text
+       .globl  foo
+       .type   foo, @function
+foo:
+.LFB0:
+       .cfi_startproc
+# BLOCK 2 seq:0
+# PRED: ENTRY (FALLTHRU)
+       pushq   %rbp
+       .cfi_def_cfa_offset 16
+       .cfi_offset 6, -16
+       movq    %rsp, %rbp
+       .cfi_def_cfa_register 6
+       movq    %rdi, -8(%rbp)
+       nop
+        pushq    $.L1
+        ret
+.L1:
+        nop
+       popq    %rbp
+       .cfi_def_cfa 7, 8
+# SUCC: EXIT [100.0%] 
+       ret
+       .cfi_endproc
+.LFE0:
+       .size   foo, .-foo
+       .globl  bar
+       .type   bar, @function
+bar:
+.LFB1:
+       .cfi_startproc
+# BLOCK 2 seq:0
+# PRED: ENTRY (FALLTHRU)
+       pushq   %rbp
+       .cfi_def_cfa_offset 16
+       .cfi_offset 6, -16
+       movq    %rsp, %rbp
+       .cfi_def_cfa_register 6
+       subq    $8, %rsp
+       movq    %rdi, -8(%rbp)
+       movq    -8(%rbp), %rax
+       movq    %rax, %rdi
+       call    foo
+       nop
+       leave
+       .cfi_def_cfa 7, 8
+# SUCC: EXIT [100.0%] 
+       ret
+       .cfi_endproc
+.LFE1:
+       .size   bar, .-bar
+       .ident  "GCC: (SUSE Linux) 7.5.0"
+       .section        .note.GNU-stack,"",@progbits