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Re: [PATCH-ping] VAX: Forced decoding of function entry masks (eg.for disassembling ROM images)
Hi Jan-Benedict,
Basically, I of course like the idea of parsing the options only
once. OTOH, this is one more location that's leaking. Maybe the
time is come to *really* implement an initializer and termination
function for the disassembler backends? But I'm not sure if it's
worth it. Disassembling used to be a slow process, and it's a rare
situation. Even on a VAX, I'd accept that it takes some time[tm]
to disassemble something. ...and with today's PCs, the overhead
of parsing the options each time /one/ opcode is being
disassembled is irrelevant.
So the pros and cons of your implementation are:
+ faster
- leaks memory
- modifies disassembler_info->disassembler_options
If somebody would implement a init/fini function for the backend, that
would turn out to only being faster with no drawbacks...
Being somewhat undecided, I'd say let's push in your version and start
a new thread about init/fini functions for the disassembler backend.
I'll push it through the compiler in the mean time.
Ok - I have pushed my version, with a few fixes to address all of the
issues you mentioned, except the memory leak. (See the attached patch).
I think that this leak is OK for now, but we should not forget it.
One day (soon I hope), I'll write the code to add the necessary hooks,
so that the leak can be removed.
Cheers
Nick
Index: opcodes/vax-dis.c
===================================================================
RCS file: /cvs/src/src/opcodes/vax-dis.c,v
retrieving revision 1.9
diff -c -3 -p -r1.9 vax-dis.c
*** opcodes/vax-dis.c 14 Mar 2005 09:35:26 -0000 1.9
--- opcodes/vax-dis.c 29 Mar 2005 16:04:47 -0000
***************
*** 17,22 ****
--- 17,24 ----
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ #include <setjmp.h>
+ #include <string.h>
#include "sysdep.h"
#include "opcode/vax.h"
#include "dis-asm.h"
*************** static char *entry_mask_bit[] =
*** 77,91 ****
/* Maximum length of an instruction. */
#define MAXLEN 25
- #include <setjmp.h>
-
struct private
{
/* Points to first byte not fetched. */
! bfd_byte *max_fetched;
! bfd_byte the_buffer[MAXLEN];
! bfd_vma insn_start;
! jmp_buf bailout;
};
/* Make sure that bytes from INFO->PRIVATE_DATA->BUFFER (inclusive)
--- 79,91 ----
/* Maximum length of an instruction. */
#define MAXLEN 25
struct private
{
/* Points to first byte not fetched. */
! bfd_byte * max_fetched;
! bfd_byte the_buffer[MAXLEN];
! bfd_vma insn_start;
! jmp_buf bailout;
};
/* Make sure that bytes from INFO->PRIVATE_DATA->BUFFER (inclusive)
*************** fetch_data (info, addr)
*** 119,124 ****
--- 119,213 ----
return 1;
}
+ /* Entry mask handling. */
+ static unsigned int entry_addr_occupied_slots = 0;
+ static unsigned int entry_addr_total_slots = 0;
+ static bfd_vma * entry_addr = NULL;
+
+ /* Parse the VAX specific disassembler options. These contain function
+ entry addresses, which can be useful to disassemble ROM images, since
+ there's no symbol table. Returns TRUE upon success, FALSE otherwise. */
+
+ static bfd_boolean
+ parse_disassembler_options (char * options)
+ {
+ const char * entry_switch = "entry:";
+
+ while ((options = strstr (options, entry_switch)))
+ {
+ options += strlen (entry_switch);
+
+ /* The greater-than part of the test below is paranoia. */
+ if (entry_addr_occupied_slots >= entry_addr_total_slots)
+ {
+ /* A guesstimate of the number of entries we will have to create. */
+ entry_addr_total_slots +=
+ strlen (options) / (strlen (entry_switch) + 5);
+
+ entry_addr = realloc (entry_addr, sizeof (bfd_vma)
+ * entry_addr_total_slots);
+ }
+
+ if (entry_addr == NULL)
+ return FALSE;
+
+ entry_addr[entry_addr_occupied_slots] = bfd_scan_vma (options, NULL, 0);
+ entry_addr_occupied_slots ++;
+ }
+
+ return TRUE;
+ }
+
+ #if 0 /* FIXME: Ideally the disassembler should have target specific
+ initialisation and termination function pointers. Then
+ parse_disassembler_options could be the init function and
+ free_entry_array (below) could be the termination routine.
+ Until then there is no way for the disassembler to tell us
+ that it has finished and that we no longer need the entry
+ array, so this routine is suppressed for now. It does mean
+ that we leak memory, but only to the extent that we do not
+ free it just before the disassembler is about to terminate
+ anyway. */
+
+ /* Free memory allocated to our entry array. */
+
+ static void
+ free_entry_array (void)
+ {
+ if (entry_addr)
+ {
+ free (entry_addr);
+ entry_addr = NULL;
+ entry_addr_occupied_slots = entry_addr_total_slots = 0;
+ }
+ }
+ #endif
+ /* Check if the given address is a known function entry. Either there must
+ be a symbol of function type at this address, or the address must be
+ a forced entry point. The later helps in disassembling ROM images, because
+ there's no symbol table at all. Forced entry points can be given by
+ supplying several -M options to objdump: -M entry:0xffbb7730. */
+
+ static bfd_boolean
+ is_function_entry (struct disassemble_info *info, bfd_vma addr)
+ {
+ unsigned int i;
+
+ /* Check if there's a BSF_FUNCTION symbol at our address. */
+ if (info->symbols
+ && info->symbols[0]
+ && (info->symbols[0]->flags & BSF_FUNCTION)
+ && addr == bfd_asymbol_value (info->symbols[0]))
+ return TRUE;
+
+ /* Check for forced function entry address. */
+ for (i = entry_addr_occupied_slots; i--;)
+ if (entry_addr[i] == addr)
+ return TRUE;
+
+ return FALSE;
+ }
+
/* Print the vax instruction at address MEMADDR in debugged memory,
on INFO->STREAM. Returns length of the instruction, in bytes. */
*************** print_insn_vax (memaddr, info)
*** 127,132 ****
--- 216,222 ----
bfd_vma memaddr;
disassemble_info *info;
{
+ static bfd_boolean parsed_disassembler_options = FALSE;
const struct vot *votp;
const char *argp;
unsigned char *arg;
*************** print_insn_vax (memaddr, info)
*** 137,142 ****
--- 227,241 ----
priv.max_fetched = priv.the_buffer;
priv.insn_start = memaddr;
+ if (! parsed_disassembler_options
+ && info->disassembler_options != NULL)
+ {
+ parse_disassembler_options (info->disassembler_options);
+
+ /* To avoid repeated parsing of these options. */
+ parsed_disassembler_options = TRUE;
+ }
+
if (setjmp (priv.bailout) != 0)
{
/* Error return. */
*************** print_insn_vax (memaddr, info)
*** 157,166 ****
}
/* Decode function entry mask. */
! if (info->symbols
! && info->symbols[0]
! && (info->symbols[0]->flags & BSF_FUNCTION)
! && memaddr == bfd_asymbol_value (info->symbols[0]))
{
int i = 0;
int register_mask = buffer[1] << 8 | buffer[0];
--- 256,262 ----
}
/* Decode function entry mask. */
! if (is_function_entry (info, memaddr))
{
int i = 0;
int register_mask = buffer[1] << 8 | buffer[0];