[RFA] dwarf2cfi.c improvements
Elena Zannoni
ezannoni@redhat.com
Wed Jun 19 06:48:00 GMT 2002
Michal Ludvig writes:
> Elena Zannoni wrote:
>
> > Could you send me a unified diff? (don't need to send it to the list
> > just to me). I'd appreciate that.
>
> Yes. Included. It's against cvs rev 1.9.
>
Since the diff had substantial changes from the previous one, I am
copying it to the list as well.
Elena
> Index: dwarf2cfi.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2cfi.c,v
> retrieving revision 1.9
> diff -u -r1.9 dwarf2cfi.c
> --- dwarf2cfi.c 11 Jun 2002 08:45:05 -0000 1.9
> +++ dwarf2cfi.c 13 Jun 2002 18:27:18 -0000
> @@ -34,7 +34,7 @@
> Frame Descriptors. */
> struct cie_unit
> {
> - /* Offset of this unit in dwarf_frame_buffer. */
> + /* Offset of this unit in .debug_frame or .eh_frame. */
> ULONGEST offset;
>
> /* A null-terminated string that identifies the augmentation to this CIE or
> @@ -176,6 +176,14 @@
> struct objfile *objfile;
> };
>
> +enum ptr_encoding {
> + PE_absptr = DW_EH_PE_absptr,
> + PE_pcrel = DW_EH_PE_pcrel,
> + PE_textrel = DW_EH_PE_textrel,
> + PE_datarel = DW_EH_PE_datarel,
> + PE_funcrel = DW_EH_PE_funcrel
> +};
> +
> #define UNWIND_CONTEXT(fi) ((struct context *) (fi->context))
>
>
> @@ -188,8 +196,6 @@
> extern unsigned int dwarf_frame_size;
> extern file_ptr dwarf_eh_frame_offset;
> extern unsigned int dwarf_eh_frame_size;
> -
> -static char *dwarf_frame_buffer;
>
>
> extern char *dwarf2_read_section (struct objfile *objfile, file_ptr offset,
> @@ -219,6 +225,7 @@
> static CORE_ADDR read_pointer (bfd * abfd, char **p);
> static CORE_ADDR read_encoded_pointer (bfd * abfd, char **p,
> unsigned char encoding);
> +static enum ptr_encoding pointer_encoding (unsigned char encoding);
>
> static LONGEST read_initial_length (bfd * abfd, char *buf, int *bytes_read);
> static ULONGEST read_length (bfd * abfd, char *buf, int *bytes_read,
> @@ -494,6 +501,9 @@
> }
> }
>
> +/* This functions only reads appropriate amount of data from *p
> + * and returns the resulting value. Calling function must handle
> + * different encoding possibilities itself! */
> static CORE_ADDR
> read_encoded_pointer (bfd * abfd, char **p, unsigned char encoding)
> {
> @@ -537,22 +547,30 @@
> "read_encoded_pointer: unknown pointer encoding");
> }
>
> - if (ret != 0)
> - switch (encoding & 0xf0)
> - {
> - case DW_EH_PE_absptr:
> - break;
> - case DW_EH_PE_pcrel:
> - ret += (CORE_ADDR) * p;
> - break;
> - case DW_EH_PE_textrel:
> - case DW_EH_PE_datarel:
> - case DW_EH_PE_funcrel:
> - default:
> - internal_error (__FILE__, __LINE__,
> - "read_encoded_pointer: unknown pointer encoding");
> - }
> + return ret;
> +}
> +
> +enum ptr_encoding
> +pointer_encoding (unsigned char encoding)
> +{
> + int ret;
>
> + if (encoding & DW_EH_PE_indirect)
> + warning ("CFI: Unsupported pointer encoding: DW_EH_PE_indirect");
> +
> + switch (encoding & 0x70)
> + {
> + case DW_EH_PE_absptr:
> + case DW_EH_PE_pcrel:
> + case DW_EH_PE_textrel:
> + case DW_EH_PE_datarel:
> + case DW_EH_PE_funcrel:
> + ret = encoding & 0x70;
> + break;
> + default:
> + internal_error (__FILE__, __LINE__,
> + "read_encoded_pointer: unknown pointer encoding");
> + }
> return ret;
> }
>
> @@ -627,6 +645,10 @@
> case DW_CFA_set_loc:
> fs->pc = read_encoded_pointer (objfile->obfd, &insn_ptr,
> fs->addr_encoding);
> +
> + if (pointer_encoding (fs->addr_encoding) != PE_absptr)
> + warning ("CFI: DW_CFA_set_loc uses relative addressing");
> +
> break;
>
> case DW_CFA_advance_loc1:
> @@ -1381,38 +1403,31 @@
>
> /* Build the cie_chunks and fde_chunks tables from informations
> in .debug_frame section. */
> -void
> -dwarf2_build_frame_info (struct objfile *objfile)
> +static void
> +parse_frame_info (struct objfile *objfile, file_ptr frame_offset,
> + unsigned int frame_size, int eh_frame)
> {
> bfd *abfd = objfile->obfd;
> + asection *curr_section_ptr;
> char *start = NULL;
> char *end = NULL;
> - int from_eh = 0;
> + char *frame_buffer = NULL;
> + char *curr_section_name, *aug_data;
> + struct cie_unit *last_cie = NULL;
> + int last_dup_fde = 0, aug_len, i;
> + CORE_ADDR curr_section_vma = 0;
>
> unwind_tmp_obstack_init ();
>
> - dwarf_frame_buffer = 0;
> -
> - if (dwarf_frame_offset)
> - {
> - dwarf_frame_buffer = dwarf2_read_section (objfile,
> - dwarf_frame_offset,
> - dwarf_frame_size);
> -
> - start = dwarf_frame_buffer;
> - end = dwarf_frame_buffer + dwarf_frame_size;
> - }
> - else if (dwarf_eh_frame_offset)
> - {
> - dwarf_frame_buffer = dwarf2_read_section (objfile,
> - dwarf_eh_frame_offset,
> - dwarf_eh_frame_size);
> + frame_buffer = dwarf2_read_section (objfile, frame_offset, frame_size);
>
> - start = dwarf_frame_buffer;
> - end = dwarf_frame_buffer + dwarf_eh_frame_size;
> + start = frame_buffer;
> + end = frame_buffer + frame_size;
>
> - from_eh = 1;
> - }
> + curr_section_name = eh_frame ? ".eh_frame" : ".debug_frame";
> + curr_section_ptr = bfd_get_section_by_name (abfd, curr_section_name);
> + if (curr_section_ptr)
> + curr_section_vma = curr_section_ptr->vma;
>
> if (start)
> {
> @@ -1420,9 +1435,8 @@
> {
> unsigned long length;
> ULONGEST cie_id;
> - ULONGEST unit_offset = start - dwarf_frame_buffer;
> - int bytes_read;
> - int dwarf64;
> + ULONGEST unit_offset = start - frame_buffer;
> + int bytes_read, dwarf64, flag_pcrel;
> char *block_end;
>
> length = read_initial_length (abfd, start, &bytes_read);
> @@ -1430,10 +1444,16 @@
> dwarf64 = (bytes_read == 12);
> block_end = start + length;
>
> + if (length == 0)
> + {
> + start = block_end;
> + continue;
> + }
> +
> cie_id = read_length (abfd, start, &bytes_read, dwarf64);
> start += bytes_read;
>
> - if ((from_eh && cie_id == 0) || is_cie (cie_id, dwarf64))
> + if ((eh_frame && cie_id == 0) || is_cie (cie_id, dwarf64))
> {
> struct cie_unit *cie = cie_unit_alloc ();
> char *aug;
> @@ -1449,87 +1469,185 @@
> start++; /* version */
>
> cie->augmentation = aug = start;
> - while (*start)
> - start++;
> - start++; /* skip past NUL */
> + while (*start++); /* Skips last NULL as well */
>
> cie->code_align = read_uleb128 (abfd, &start);
> cie->data_align = read_sleb128 (abfd, &start);
> cie->ra = read_1u (abfd, &start);
>
> + /* Augmentation:
> + z Indicates that a uleb128 is present to size the
> + augmentation section.
> + L Indicates the encoding (and thus presence) of
> + an LSDA pointer in the FDE augmentation.
> + R Indicates a non-default pointer encoding for
> + FDE code pointers.
> + P Indicates the presence of an encoding + language
> + personality routine in the CIE augmentation.
> +
> + [This info comes from GCC's dwarf2out.c]
> + */
> if (*aug == 'z')
> {
> - int xtra = read_uleb128 (abfd, &start);
> - start += xtra;
> + aug_len = read_uleb128 (abfd, &start);
> + aug_data = start;
> + start += aug_len;
> ++aug;
> }
>
> + cie->data = start;
> + cie->data_length = block_end - cie->data;
> +
> while (*aug != '\0')
> {
> if (aug[0] == 'e' && aug[1] == 'h')
> {
> - start += sizeof (void *);
> - aug += 2;
> + aug_data += sizeof (void *);
> + aug++;
> }
> else if (aug[0] == 'R')
> + cie->addr_encoding = *aug_data++;
> + else if (aug[0] == 'P')
> {
> - cie->addr_encoding = *start++;
> - aug += 1;
> + CORE_ADDR pers_addr;
> + int pers_addr_enc;
> +
> + pers_addr_enc = *aug_data++;
> + /* We don't need pers_addr value and so we
> + don't care about it's encoding. */
> + pers_addr = read_encoded_pointer (abfd, &aug_data,
> + pers_addr_enc);
> }
> - else if (aug[0] == 'P')
> + else if (aug[0] == 'L' && eh_frame)
> {
> - CORE_ADDR ptr;
> - ptr = read_encoded_pointer (abfd, &start,
> - cie->addr_encoding);
> - aug += 1;
> + int lsda_addr_enc;
> +
> + /* Perhaps we should save this to CIE for later use?
> + Do we need it for something in GDB? */
> + lsda_addr_enc = *aug_data++;
> }
> else
> - warning ("%s(): unknown augmentation", __func__);
> + warning ("CFI warning: unknown augmentation \"%c\""
> + " in \"%s\" of\n"
> + "\t%s", aug[0], curr_section_name,
> + objfile->name);
> + aug++;
> }
>
> - cie->data = start;
> - cie->data_length = block_end - start;
> + last_cie = cie;
> }
> else
> {
> struct fde_unit *fde;
> struct cie_unit *cie;
> + int dup = 0;
> + CORE_ADDR init_loc;
>
> - fde_chunks_need_space ();
> - fde = fde_unit_alloc ();
> + /* We assume that debug_frame is in order
> + CIE,FDE,CIE,FDE,FDE,... and thus the CIE for this FDE
> + should be stored in last_cie pointer. If not, we'll
> + try to find it by the older way. */
> + if (last_cie)
> + cie = last_cie;
> + else
> + {
> + warning ("CFI: last_cie == NULL. "
> + "Perhaps a malformed %s section in '%s'...?\n",
> + curr_section_name, objfile->name);
> +
> + cie = cie_chunks;
> + while (cie)
> + {
> + if (cie->objfile == objfile)
> + {
> + if (eh_frame &&
> + (cie->offset ==
> + (unit_offset + bytes_read - cie_id)))
> + break;
> + if (!eh_frame && (cie->offset == cie_id))
> + break;
> + }
>
> - fde_chunks.array[fde_chunks.elems++] = fde;
> + cie = cie->next;
> + }
> + if (!cie)
> + error ("CFI: can't find CIE pointer");
> + }
>
> - fde->initial_location = read_pointer (abfd, &start)
> - + ANOFFSET (objfile->section_offsets,
> - SECT_OFF_TEXT (objfile));
> - fde->address_range = read_pointer (abfd, &start);
> + init_loc = read_encoded_pointer (abfd, &start,
> + cie->addr_encoding);
>
> - cie = cie_chunks;
> - while (cie)
> - {
> - if (cie->objfile == objfile)
> - {
> - if (from_eh
> - && (cie->offset ==
> - (unit_offset + bytes_read - cie_id)))
> + switch (pointer_encoding (cie->addr_encoding))
> + {
> + case PE_absptr:
> break;
> - if (!from_eh && (cie->offset == cie_id))
> + case PE_pcrel:
> + /* start-frame_buffer gives offset from
> + the beginning of actual section. */
> + init_loc += curr_section_vma + start - frame_buffer;
> break;
> - }
> + default:
> + warning ("CFI: Unsupported pointer encoding\n");
> + }
>
> - cie = cie->next;
> + /* For relocatable objects we must add an offset telling
> + where the section is actually mapped in the memory. */
> + init_loc += ANOFFSET (objfile->section_offsets,
> + SECT_OFF_TEXT (objfile));
> +
> + /* If we have both .debug_frame and .eh_frame present in
> + a file, we must eliminate duplicate FDEs. For now we'll
> + run through all entries in fde_chunks and check it one
> + by one. Perhaps in the future we can implement a faster
> + searching algorithm. */
> + /* eh_frame==2 indicates, that this file has an already
> + parsed .debug_frame too. When eh_frame==1 it means, that no
> + .debug_frame is present and thus we don't need to check for
> + duplicities. eh_frame==0 means, that we parse .debug_frame
> + and don't need to care about duplicate FDEs, because
> + .debug_frame is parsed first. */
> + for (i = 0; eh_frame == 2 && i < fde_chunks.elems; i++)
> + {
> + /* We assume that FDEs in .debug_frame and .eh_frame
> + have the same order (if they are present, of course).
> + If we find a duplicate entry for one FDE and save
> + it's index to last_dup_fde it's very likely, that
> + we'll find an entry for the following FDE right after
> + the previous one. Thus in many cases we'll run this
> + loop only once. */
> + last_dup_fde = (last_dup_fde + i) % fde_chunks.elems;
> + if (fde_chunks.array[last_dup_fde]->initial_location
> + == init_loc)
> + {
> + dup = 1;
> + break;
> + }
> }
>
> - if (!cie)
> - error ("%s(): can't find CIE pointer", __func__);
> - fde->cie_ptr = cie;
> + /* Allocate a new entry only if this FDE isn't a duplicate of
> + something we have already seen. */
> + if (!dup)
> + {
> + fde_chunks_need_space ();
> + fde = fde_unit_alloc ();
> +
> + fde_chunks.array[fde_chunks.elems++] = fde;
> +
> + fde->initial_location = init_loc;
> + fde->address_range = read_encoded_pointer (abfd, &start,
> + cie->
> + addr_encoding);
> +
> + fde->cie_ptr = cie;
>
> - if (cie->augmentation[0] == 'z')
> - read_uleb128 (abfd, &start);
> + /* Here we intentionally ignore augmentation data
> + from FDE, because we don't need them. */
> + if (cie->augmentation[0] == 'z')
> + start += read_uleb128 (abfd, &start);
>
> - fde->data = start;
> - fde->data_length = block_end - start;
> + fde->data = start;
> + fde->data_length = block_end - start;
> + }
> }
> start = block_end;
> }
> @@ -1537,7 +1655,30 @@
> sizeof (struct fde_unit *), compare_fde_unit);
> }
> }
> -
> +
> +/* We must parse both .debug_frame section and .eh_frame because
> + not all frames must be present in both of these sections. */
> +void
> +dwarf2_build_frame_info (struct objfile *objfile)
> +{
> + int after_debug_frame=0;
> +
> + /* If we have .debug_frame then the parser is called with
> + eh_frame==0 for .debug_frame and eh_frame==2 for .eh_frame,
> + otherwise it's only called once for .eh_frame with argument
> + eh_frame==1 */
> +
> + if (dwarf_frame_offset)
> + {
> + parse_frame_info (objfile, dwarf_frame_offset,
> + dwarf_frame_size, 0 /* = debug_frame */);
> + after_debug_frame = 1;
> + }
> +
> + if (dwarf_eh_frame_offset)
> + parse_frame_info (objfile, dwarf_eh_frame_offset, dwarf_eh_frame_size,
> + 1 /* = eh_frame */ + after_debug_frame);
> +}
>
> /* Return the frame address. */
> CORE_ADDR
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