Re: [RFC] Partial support for dwarf3 DW_AT_ranges

Daniel Jacobowitz
2003-01-30T00:51:54Z

On Wed, Jan 29, 2003 at 01:13:36PM -0500, Elena Zannoni wrote:
> If you have time, I'd appreciate it. I have adapted the patch to the
> current sources, but even with it, I wasn't able to make Jakub's
> example work. The example is in PR 833.
> I can send you the diffs I have, if it helps.

This is pretty similar to what you sent me, cleaned up a little to
match my reading of the standard. It works to fix my testcase for PR
gdb/961, which is a simpler case of disappearing local variables.
I'll submit that for the testsuite separately but I don't know quite
how to do it yet; the problem is not going to show up if you don't have
optimization.

This doesn't solve PR gdb/833, for the reasons outlined in my previous
message.

How does this patch look?

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer

2003-01-29 Richard Henderson <rth@redhat.com>
Elena Zannoni <ezannoni@redhat.com>
Daniel Jacobowitz <drow@mvista.com>

Fix PR gdb/961.
* dwarf2read.c (dwarf_ranges_offset, dwarf_ranges_size): New
variables.
(RANGES_SECTION): New.
(dwarf_ranges_buffer): New variable.
(struct comp_unit_head): Add member "die".
(struct dwarf2_pinfo): Add dwarf_ranges_buffer, dwarf_ranges_size.
(DWARF_RANGES_BUFFER, DWARF_RANGES_SIZE): New.
(dwarf2_has_info): Init dwarf_ranges_offset and dwarf_ranges_size.
(dwarf2_locate_sections): Likewise.
(dwarf2_build_psymtabs): Read .debug_ranges.
(dwarf2_build_psymtabs_hard): Swap dwarf_ranges out.
(psymtab_to_symtab_1): Swap dwarf_ranges in. Set cu_header.die.
(RANGES_SECTION): New.
(dwarf2_get_pc_bounds): New cu_header argument; adjust all callers.
Look for DW_AT_ranges and return the bounding box.

Index: dwarf2read.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/dwarf2read.c,v
retrieving revision 1.79
diff -u -p -r1.79 dwarf2read.c
--- dwarf2read.c 18 Jan 2003 15:55:51 -0000 1.79
+++ dwarf2read.c 30 Jan 2003 00:41:19 -0000
@@ -133,6 +133,7 @@ static file_ptr dwarf_aranges_offset;
static file_ptr dwarf_loc_offset;
static file_ptr dwarf_macinfo_offset;
static file_ptr dwarf_str_offset;
+static file_ptr dwarf_ranges_offset;
file_ptr dwarf_frame_offset;
file_ptr dwarf_eh_frame_offset;

@@ -144,6 +145,7 @@ static unsigned int dwarf_aranges_size;
static unsigned int dwarf_loc_size;
static unsigned int dwarf_macinfo_size;
static unsigned int dwarf_str_size;
+static unsigned int dwarf_ranges_size;
unsigned int dwarf_frame_size;
unsigned int dwarf_eh_frame_size;

@@ -157,6 +159,7 @@ unsigned int dwarf_eh_frame_size;
#define LOC_SECTION ".debug_loc"
#define MACINFO_SECTION ".debug_macinfo"
#define STR_SECTION ".debug_str"
+#define RANGES_SECTION ".debug_ranges"
#define FRAME_SECTION ".debug_frame"
#define EH_FRAME_SECTION ".eh_frame"

@@ -202,6 +205,10 @@ struct comp_unit_head
/* DWARF abbreviation table associated with this compilation unit */

struct abbrev_info *dwarf2_abbrevs[ABBREV_HASH_SIZE];
+
+ /* Pointer to the DIE associated with the compilation unit. */
+
+ struct die_info *die;
};

/* The line number information for a compilation unit (found in the
@@ -373,6 +380,7 @@ static char *dwarf_abbrev_buffer;
static char *dwarf_line_buffer;
static char *dwarf_str_buffer;
static char *dwarf_macinfo_buffer;
+static char *dwarf_ranges_buffer;

/* A zeroed version of a partial die for initialization purposes. */
static struct partial_die_info zeroed_partial_die;
@@ -481,6 +489,14 @@ struct dwarf2_pinfo

unsigned int dwarf_macinfo_size;

+ /* Pointer to start of dwarf ranges buffer for the objfile. */
+
+ char *dwarf_ranges_buffer;
+
+ /* Size of dwarf ranges buffer for the objfile. */
+
+ unsigned int dwarf_ranges_size;
+
};

#define PST_PRIVATE(p) ((struct dwarf2_pinfo *)(p)->read_symtab_private)
@@ -494,6 +510,8 @@ struct dwarf2_pinfo
#define DWARF_STR_SIZE(p) (PST_PRIVATE(p)->dwarf_str_size)
#define DWARF_MACINFO_BUFFER(p) (PST_PRIVATE(p)->dwarf_macinfo_buffer)
#define DWARF_MACINFO_SIZE(p) (PST_PRIVATE(p)->dwarf_macinfo_size)
+#define DWARF_RANGES_BUFFER(p) (PST_PRIVATE(p)->dwarf_ranges_buffer)
+#define DWARF_RANGES_SIZE(p) (PST_PRIVATE(p)->dwarf_ranges_size)

/* Maintain an array of referenced fundamental types for the current
compilation unit being read. For DWARF version 1, we have to construct
@@ -751,7 +769,8 @@ static void read_lexical_block_scope (st
const struct comp_unit_head *);

static int dwarf2_get_pc_bounds (struct die_info *,
- CORE_ADDR *, CORE_ADDR *, struct objfile *);
+ CORE_ADDR *, CORE_ADDR *, struct objfile *,
+ const struct comp_unit_head *);

static void dwarf2_add_field (struct field_info *, struct die_info *,
struct objfile *, const struct comp_unit_head *);
@@ -886,6 +905,8 @@ dwarf2_has_info (bfd *abfd)
dwarf_macinfo_offset = 0;
dwarf_frame_offset = 0;
dwarf_eh_frame_offset = 0;
+ dwarf_ranges_offset = 0;
+
bfd_map_over_sections (abfd, dwarf2_locate_sections, NULL);
if (dwarf_info_offset && dwarf_abbrev_offset)
{
@@ -954,6 +975,11 @@ dwarf2_locate_sections (bfd *ignore_abfd
dwarf_eh_frame_offset = sectp->filepos;
dwarf_eh_frame_size = bfd_get_section_size_before_reloc (sectp);
}
+ else if (STREQ (sectp->name, RANGES_SECTION))
+ {
+ dwarf_ranges_offset = sectp->filepos;
+ dwarf_ranges_size = bfd_get_section_size_before_reloc (sectp);
+ }
}

/* Build a partial symbol table. */
@@ -992,6 +1018,13 @@ dwarf2_build_psymtabs (struct objfile *o
else
dwarf_macinfo_buffer = NULL;

+ if (dwarf_ranges_offset)
+ dwarf_ranges_buffer = dwarf2_read_section (objfile,
+ dwarf_ranges_offset,
+ dwarf_ranges_size);
+ else
+ dwarf_ranges_buffer = NULL;
+
if (mainline
|| (objfile->global_psymbols.size == 0
&& objfile->static_psymbols.size == 0))
@@ -1207,6 +1240,8 @@ dwarf2_build_psymtabs_hard (struct objfi
DWARF_STR_SIZE (pst) = dwarf_str_size;
DWARF_MACINFO_BUFFER (pst) = dwarf_macinfo_buffer;
DWARF_MACINFO_SIZE (pst) = dwarf_macinfo_size;
+ DWARF_RANGES_BUFFER (pst) = dwarf_ranges_buffer;
+ DWARF_RANGES_SIZE (pst) = dwarf_ranges_size;
baseaddr = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));

/* Store the function that reads in the rest of the symbol table */
@@ -1543,6 +1578,8 @@ psymtab_to_symtab_1 (struct partial_symt
dwarf_str_size = DWARF_STR_SIZE (pst);
dwarf_macinfo_buffer = DWARF_MACINFO_BUFFER (pst);
dwarf_macinfo_size = DWARF_MACINFO_SIZE (pst);
+ dwarf_ranges_buffer = DWARF_RANGES_BUFFER (pst);
+ dwarf_ranges_size = DWARF_RANGES_SIZE (pst);
baseaddr = ANOFFSET (pst->section_offsets, SECT_OFF_TEXT (objfile));
cu_header_offset = offset;
info_ptr = dwarf_info_buffer + offset;
@@ -1565,9 +1602,10 @@ psymtab_to_symtab_1 (struct partial_symt
make_cleanup_free_die_list (dies);

/* Do line number decoding in read_file_scope () */
+ cu_header.die = dies;
process_die (dies, objfile, &cu_header);

- if (!dwarf2_get_pc_bounds (dies, &lowpc, &highpc, objfile))
+ if (!dwarf2_get_pc_bounds (dies, &lowpc, &highpc, objfile, &cu_header))
{
/* Some compilers don't define a DW_AT_high_pc attribute for
the compilation unit. If the DW_AT_high_pc is missing,
@@ -1582,7 +1620,8 @@ psymtab_to_symtab_1 (struct partial_symt
{
CORE_ADDR low, high;

- if (dwarf2_get_pc_bounds (child_die, &low, &high, objfile))
+ if (dwarf2_get_pc_bounds (child_die, &low, &high,
+ objfile, &cu_header))
{
highpc = max (highpc, high);
}
@@ -1711,7 +1750,7 @@ read_file_scope (struct die_info *die, s
bfd *abfd = objfile->obfd;
struct line_header *line_header = 0;

- if (!dwarf2_get_pc_bounds (die, &lowpc, &highpc, objfile))
+ if (!dwarf2_get_pc_bounds (die, &lowpc, &highpc, objfile, cu_header))
{
if (die->has_children)
{
@@ -1722,7 +1761,8 @@ read_file_scope (struct die_info *die, s
{
CORE_ADDR low, high;

- if (dwarf2_get_pc_bounds (child_die, &low, &high, objfile))
+ if (dwarf2_get_pc_bounds (child_die, &low, &high,
+ objfile, cu_header))
{
lowpc = min (lowpc, low);
highpc = max (highpc, high);
@@ -1868,7 +1908,7 @@ read_func_scope (struct die_info *die, s

/* Ignore functions with missing or empty names and functions with
missing or invalid low and high pc attributes. */
- if (name == NULL || !dwarf2_get_pc_bounds (die, &lowpc, &highpc, objfile))
+ if (name == NULL || !dwarf2_get_pc_bounds (die, &lowpc, &highpc, objfile, cu_header))
return;

lowpc += baseaddr;
@@ -1966,7 +2006,11 @@ read_lexical_block_scope (struct die_inf
struct die_info *child_die;

/* Ignore blocks with missing or invalid low and high pc attributes. */
- if (!dwarf2_get_pc_bounds (die, &lowpc, &highpc, objfile))
+ /* ??? Perhaps consider discontiguous blocks defined by DW_AT_ranges
+ as multiple lexical blocks? Handling children in a sane way would
+ be nasty. Might be easier to properly extend generic blocks to
+ describe ranges. */
+ if (!dwarf2_get_pc_bounds (die, &lowpc, &highpc, objfile, cu_header))
return;
lowpc += baseaddr;
highpc += baseaddr;
@@ -1991,27 +2035,159 @@ read_lexical_block_scope (struct die_inf
local_symbols = new->locals;
}

-/* Get low and high pc attributes from a die.
- Return 1 if the attributes are present and valid, otherwise, return 0. */
-
+/* Get low and high pc attributes from a die. Return 1 if the attributes
+ are present and valid, otherwise, return 0. Return -1 if the range is
+ discontinuous, i.e. derived from DW_AT_ranges information. */
static int
-dwarf2_get_pc_bounds (struct die_info *die, CORE_ADDR *lowpc, CORE_ADDR *highpc,
- struct objfile *objfile)
+dwarf2_get_pc_bounds (struct die_info *die, CORE_ADDR *lowpc,
+ CORE_ADDR *highpc, struct objfile *objfile,
+ const struct comp_unit_head *cu_header)
{
struct attribute *attr;
- CORE_ADDR low;
- CORE_ADDR high;
+ bfd *obfd = objfile->obfd;
+ CORE_ADDR low = 0;
+ CORE_ADDR high = 0;
+ int ret = 0;

- attr = dwarf_attr (die, DW_AT_low_pc);
- if (attr)
- low = DW_ADDR (attr);
- else
- return 0;
attr = dwarf_attr (die, DW_AT_high_pc);
if (attr)
- high = DW_ADDR (attr);
+ {
+ high = DW_ADDR (attr);
+ attr = dwarf_attr (die, DW_AT_low_pc);
+ if (attr)
+ low = DW_ADDR (attr);
+ else
+ /* Found high w/o low attribute. */
+ return 0;
+
+ /* Found consecutive range of addresses. */
+ ret = 1;
+ }
else
- return 0;
+ {
+ attr = dwarf_attr (die, DW_AT_ranges);
+ if (attr != NULL)
+ {
+ unsigned int addr_size = cu_header->addr_size;
+ CORE_ADDR mask = ~(~(CORE_ADDR)1 << (addr_size * 8 - 1));
+ /* Value of the DW_AT_ranges attribute is the offset in the
+ .debug_renges section. */
+ unsigned int offset = DW_UNSND (attr);
+ /* Base address selection entry. */
+ CORE_ADDR base = 0;
+ int found_base = 0;
+ int dummy;
+ unsigned int i;
+ char *buffer;
+ CORE_ADDR marker;
+ int low_set;
+
+ /* The applicable base address is determined by (1) the closest
+ preceding base address selection entry in the range list or
+ (2) the DW_AT_low_pc of the compilation unit. */
+
+ /* ??? Was in dwarf3 draft4, and has since been removed.
+ GCC still uses it though. */
+ attr = dwarf_attr (cu_header->die, DW_AT_entry_pc);
+ if (attr)
+ {
+ base = DW_ADDR (attr);
+ found_base = 1;
+ }
+
+ if (!found_base)
+ {
+ attr = dwarf_attr (cu_header->die, DW_AT_low_pc);
+ if (attr)
+ {
+ base = DW_ADDR (attr);
+ found_base = 1;
+ }
+ }
+
+ buffer = dwarf_ranges_buffer + offset;
+
+
+ /* Read in the largest possible address. */
+ marker = read_address (obfd, buffer, cu_header, &dummy);
+ if ((marker & mask) == mask)
+ {
+ /* If we found the largest possible address, then
+ read the base address. */
+ base = read_address (obfd, buffer + addr_size,
+ cu_header, &dummy);
+ buffer += 2 * addr_size;
+ offset += 2 * addr_size;
+ found_base = 1;
+ }
+
+ low_set = 0;
+
+ while (1)
+ {
+ CORE_ADDR range_beginning, range_end;
+
+ range_beginning = read_address (obfd, buffer,
+ cu_header, &dummy);
+ buffer += addr_size;
+ range_end = read_address (obfd, buffer, cu_header, &dummy);
+ buffer += addr_size;
+ offset += 2 * addr_size;
+
+ /* An end of list marker is a pair of zero addresses. */
+ if (range_beginning == 0 && range_end == 0)
+ /* Found the end of list entry. */
+ break;
+
+ /* Each base address selection entry is a pair of 2 values.
+ The first is the largest possible address, the second is
+ the base address. Check for a base address here. */
+ if ((range_beginning & mask) == mask)
+ {
+ /* If we found the largest possible address, then
+ read the base address. */
+ base = read_address (obfd, buffer + addr_size,
+ cu_header, &dummy);
+ found_base = 1;
+ continue;
+ }
+
+ if (!found_base)
+ {
+ /* We have no valid base address for the ranges
+ data. */
+ complaint (&symfile_complaints,
+ "Invalid .debug_ranges data (no base address)");
+ return 0;
+ }
+
+ /* FIXME: This is recording everything as a low-high
+ segment of consecutive addresses. We should have a
+ data structure for discontiguous block ranges
+ instead. */
+ if (! low_set)
+ {
+ low = range_beginning;
+ high = range_end;
+ low_set = 1;
+ }
+ else
+ {
+ if (range_beginning < low)
+ low = range_beginning;
+ if (range_end > high)
+ high = range_end;
+ }
+ }
+
+ if (! low_set)
+ /* If the first entry is an end-of-list marker, the range
+ describes an empty scope, i.e. no instructions. */
+ return 0;
+
+ ret = -1;
+ }
+ }

if (high < low)
return 0;
@@ -2024,12 +2200,12 @@ dwarf2_get_pc_bounds (struct die_info *d
labels are not in the output, so the relocs get a value of 0.
If this is a discarded function, mark the pc bounds as invalid,
so that GDB will ignore it. */
- if (low == 0 && (bfd_get_file_flags (objfile->obfd) & HAS_RELOC) == 0)
+ if (low == 0 && (bfd_get_file_flags (obfd) & HAS_RELOC) == 0)
return 0;

*lowpc = low;
*highpc = high;
- return 1;
+ return ret;
}

/* Add an aggregate field to the field list. */