Message ID | 1524928992-18156-1-git-send-email-mark@klomp.org |
---|---|
State | New |
Headers | show |
Series | DWARF: Add .debug_addr table header for dwarf_version >= 5. | expand |
> index d3d925d..51d0ca4 100644 > --- a/gcc/dwarf2out.c > +++ b/gcc/dwarf2out.c > @@ -31293,6 +31293,21 @@ dwarf2out_finish (const char *) > } > > switch_to_section (debug_addr_section); > + /* GNU DebugFission didn't have a header for .debug_addr. */ > + if (dwarf_version >= 5) That sounds LLVMish... Did you mean -gsplit-dwarf instead?
Hi Eric, On Sat, 2018-04-28 at 18:00 +0200, Eric Botcazou wrote: > > index d3d925d..51d0ca4 100644 > > --- a/gcc/dwarf2out.c > > +++ b/gcc/dwarf2out.c > > @@ -31293,6 +31293,21 @@ dwarf2out_finish (const char *) > > } > > > > switch_to_section (debug_addr_section); > > + /* GNU DebugFission didn't have a header for .debug_addr. */ > > + if (dwarf_version >= 5) > > That sounds LLVMish... Did you mean -gsplit-dwarf instead? I don't know what LLVMish does, or whether it implements the GNU DebugFission variant of split DWARF, the DWARF5 variant or something else. For GCC -gsplit-dwarf generates GNU DebugFission output (including .debug_addr) for older DWARF versions. It is described here: https://gcc.gnu.org/wiki/DebugFission This got standardized for DWARF5. But there are some differences. One particular change is that GNU DebugFission doesn't have address table headers in .debug_addr sections. But DWARF5 does. This patch fixes that. Or did you mean that you expected the code to be guarded by if (dwarf_split_debug_info)? It is, just a bit higher up in the code. Cheers, Mark
On Sat, Apr 28, 2018 at 05:23:12PM +0200, Mark Wielaard wrote: > GNU DebugFission didn't add table headers for the .debug_addr > tables, but DWARF5 does. The table header make it possible > for a DWARF consumer to parse the address tables without having > to index all .debug_info CUs first. We can keep using the > .debug_addr section label as is, because the DW_AT_addr_base > attribute points at the actual address index, which starts > right after the table header. So the label is generated at > the correct location whether the header is added first or not. > > gcc/ChangeLog > > * dwarf2out.c (dwarf2out_finish): Add .debug_addr table header for > dwarf_version >= 5. > > diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c > index d3d925d..51d0ca4 100644 > --- a/gcc/dwarf2out.c > +++ b/gcc/dwarf2out.c > @@ -31293,6 +31293,21 @@ dwarf2out_finish (const char *) > } > > switch_to_section (debug_addr_section); > + /* GNU DebugFission didn't have a header for .debug_addr. */ > + if (dwarf_version >= 5) > + { > + unsigned long addrs_length = > + addr_index_table->elements () * DWARF2_ADDR_SIZE + 4; No = at the end of line, it should be at the start of the next line, i.e. unsigned long addrs_length = addr_index_table->elements () * DWARF2_ADDR_SIZE + 4; > + > + if (DWARF_INITIAL_LENGTH_SIZE - DWARF_OFFSET_SIZE == 4) > + dw2_asm_output_data (4, 0xffffffff, > + "Escape value for 64-bit DWARF extension"); > + dw2_asm_output_data (DWARF_OFFSET_SIZE, addrs_length, > + "Length of Address Unit"); > + dw2_asm_output_data (2, 5, "DWARF addr version"); > + dw2_asm_output_data (1, DWARF2_ADDR_SIZE, "Size of Address"); > + dw2_asm_output_data (1, 0, "Size of Segment Descriptor"); > + } > ASM_OUTPUT_LABEL (asm_out_file, debug_addr_section_label); > output_addr_table (); > } Shouldn't we together with the addition of the .debug_addr section header also switch to using DW_AT_addr_base rather than DW_AT_GNU_addr_base, i.e. add DW_AT_addr_base into dwarf_AT and use dwarf_AT (DW_AT_addr_base) instead of DW_AT_GNU_addr_base? Jakub
> I don't know what LLVMish does, or whether it implements the GNU > DebugFission variant of split DWARF, the DWARF5 variant or something > else. For GCC -gsplit-dwarf generates GNU DebugFission output > (including .debug_addr) for older DWARF versions. > It is described here: https://gcc.gnu.org/wiki/DebugFission Yes, that's what I was referring to. DebugFission is the name of the Wiki page so let's use "GNU split DWARF" or -gsplit-dwarf in the comment please.
On Sat, Apr 28, 2018 at 06:36:02PM +0200, Jakub Jelinek wrote: > On Sat, Apr 28, 2018 at 05:23:12PM +0200, Mark Wielaard wrote: > > switch_to_section (debug_addr_section); > > + /* GNU DebugFission didn't have a header for .debug_addr. */ > > + if (dwarf_version >= 5) > > + { > > + unsigned long addrs_length = > > + addr_index_table->elements () * DWARF2_ADDR_SIZE + 4; > > No = at the end of line, it should be at the start of the next line, i.e. > unsigned long addrs_length > = addr_index_table->elements () * DWARF2_ADDR_SIZE + 4; Oops. Fixed. > > + if (DWARF_INITIAL_LENGTH_SIZE - DWARF_OFFSET_SIZE == 4) > > + dw2_asm_output_data (4, 0xffffffff, > > + "Escape value for 64-bit DWARF extension"); > > + dw2_asm_output_data (DWARF_OFFSET_SIZE, addrs_length, > > + "Length of Address Unit"); > > + dw2_asm_output_data (2, 5, "DWARF addr version"); > > + dw2_asm_output_data (1, DWARF2_ADDR_SIZE, "Size of Address"); > > + dw2_asm_output_data (1, 0, "Size of Segment Descriptor"); > > + } > > ASM_OUTPUT_LABEL (asm_out_file, debug_addr_section_label); > > output_addr_table (); > > } > > Shouldn't we together with the addition of the .debug_addr section header > also switch to using DW_AT_addr_base rather than DW_AT_GNU_addr_base, i.e. > add DW_AT_addr_base into dwarf_AT and use dwarf_AT (DW_AT_addr_base) > instead of DW_AT_GNU_addr_base? Yes of course. I was actually checking the DWARF version of the CU, but having the correct attribute is obviously better. Updated patch: GNU DebugFission didn't add table headers for the .debug_addr tables, but DWARF5 does. The table header makes it possible for a DWARF consumer to parse the address tables without having to index all .debug_info CUs first. We can keep using the .debug_addr section label as is, because the DW_AT_[GNU_]addr_base attribute points at the actual address index, which starts right after the table header. So the label is generated at the correct location whether the header is added first or not. Add DW_AT_addr_base instead of DW_AT_GNU_addr_base to the skeleton CU DIE for DWARF5. gcc/ChangeLog * dwarf2out.c (dwarf2out_finish): Add .debug_addr table header for dwarf_version >= 5. (dwarf_AT): Handle DW_AT_addr_base. (add_top_level_skeleton_die_attrs): Use dwarf_AT for DW_AT_addr_base. diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c index d3d925d..c172387 100644 --- a/gcc/dwarf2out.c +++ b/gcc/dwarf2out.c @@ -1724,6 +1724,11 @@ dwarf_AT (enum dwarf_attribute at) return DW_AT_GNU_dwo_name; break; + case DW_AT_addr_base: + if (dwarf_version < 5) + return DW_AT_GNU_addr_base; + break; + default: break; } @@ -11106,7 +11111,7 @@ add_top_level_skeleton_die_attrs (dw_die_ref die) if (comp_dir != NULL) add_skeleton_AT_string (die, DW_AT_comp_dir, comp_dir); add_AT_pubnames (die); - add_AT_lineptr (die, DW_AT_GNU_addr_base, debug_addr_section_label); + add_AT_lineptr (die, dwarf_AT (DW_AT_addr_base), debug_addr_section_label); } /* Output skeleton debug sections that point to the dwo file. */ @@ -31293,6 +31298,21 @@ dwarf2out_finish (const char *) } switch_to_section (debug_addr_section); + /* GNU DebugFission didn't have a header for .debug_addr. */ + if (dwarf_version >= 5) + { + unsigned long addrs_length + = addr_index_table->elements () * DWARF2_ADDR_SIZE + 4; + + if (DWARF_INITIAL_LENGTH_SIZE - DWARF_OFFSET_SIZE == 4) + dw2_asm_output_data (4, 0xffffffff, + "Escape value for 64-bit DWARF extension"); + dw2_asm_output_data (DWARF_OFFSET_SIZE, addrs_length, + "Length of Address Unit"); + dw2_asm_output_data (2, 5, "DWARF addr version"); + dw2_asm_output_data (1, DWARF2_ADDR_SIZE, "Size of Address"); + dw2_asm_output_data (1, 0, "Size of Segment Descriptor"); + } ASM_OUTPUT_LABEL (asm_out_file, debug_addr_section_label); output_addr_table (); }
On Sat, Apr 28, 2018 at 09:01:45PM +0200, Mark Wielaard wrote: > gcc/ChangeLog > > * dwarf2out.c (dwarf2out_finish): Add .debug_addr table header for > dwarf_version >= 5. > (dwarf_AT): Handle DW_AT_addr_base. > (add_top_level_skeleton_die_attrs): Use dwarf_AT for DW_AT_addr_base. Ok for trunk. Jakub
On Sat, Apr 28, 2018 at 08:54:00PM +0200, Eric Botcazou wrote: > > I don't know what LLVMish does, or whether it implements the GNU > > DebugFission variant of split DWARF, the DWARF5 variant or something > > else. For GCC -gsplit-dwarf generates GNU DebugFission output > > (including .debug_addr) for older DWARF versions. > > It is described here: https://gcc.gnu.org/wiki/DebugFission > > Yes, that's what I was referring to. DebugFission is the name of the Wiki > page so let's use "GNU split DWARF" or -gsplit-dwarf in the comment please. -gsplit-dwarf is not appropriate, because that includes the DWARF5 variant thereof. GNU split DWARF extension is ok. Jakub
On Sat, Apr 28, 2018 at 08:54:00PM +0200, Eric Botcazou wrote: > > For GCC -gsplit-dwarf generates GNU DebugFission output > > (including .debug_addr) for older DWARF versions. > > It is described here: https://gcc.gnu.org/wiki/DebugFission > > Yes, that's what I was referring to. DebugFission is the name of the Wiki > page so let's use "GNU split DWARF" or -gsplit-dwarf in the comment please. I expanded the comment into a little paragraph explaining the terminology used and included the URL for background information. Hope that makes things more clear. Thanks, Mark
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c index d3d925d..51d0ca4 100644 --- a/gcc/dwarf2out.c +++ b/gcc/dwarf2out.c @@ -31293,6 +31293,21 @@ dwarf2out_finish (const char *) } switch_to_section (debug_addr_section); + /* GNU DebugFission didn't have a header for .debug_addr. */ + if (dwarf_version >= 5) + { + unsigned long addrs_length = + addr_index_table->elements () * DWARF2_ADDR_SIZE + 4; + + if (DWARF_INITIAL_LENGTH_SIZE - DWARF_OFFSET_SIZE == 4) + dw2_asm_output_data (4, 0xffffffff, + "Escape value for 64-bit DWARF extension"); + dw2_asm_output_data (DWARF_OFFSET_SIZE, addrs_length, + "Length of Address Unit"); + dw2_asm_output_data (2, 5, "DWARF addr version"); + dw2_asm_output_data (1, DWARF2_ADDR_SIZE, "Size of Address"); + dw2_asm_output_data (1, 0, "Size of Segment Descriptor"); + } ASM_OUTPUT_LABEL (asm_out_file, debug_addr_section_label); output_addr_table (); }