[RFA] Runtime Dwarf2 CFI engine cleanup

Michal Ludvig
2003-01-06T12:55:04Z

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Hi all,
the attached is a fix for the problem described here:
http://sources.redhat.com/ml/gdb/2002-12/msg00246.html

I've created a new function cleanup_cfi() in dwarf2cfi.c that deletes
all CIEs and FDEs of objfiles removed later by objfile_purge_solibs().
So far it works fine but I don't know how should I correctly call it.
For now I put the call directly to run_command():

static void
run_command (char *args, int from_tty)
{
[...]
clear_breakpoint_hit_counts ();

cleanup_cfi (); /* <=== HERE */

objfile_purge_solibs ();

do_run_cleanups (NULL);

reopen_exec_file ();
reread_symbols ();
[...]
}

I know it isn't the right solution because it would require linking of
dwarf2cfi.o to all targets. If I would wrap it by #ifdef X86_64 ...
#endif it still isn't perfect, because other archs will hopefully use
CFI in the future as well.

I was thinking about defining something like USE_DWARF2CFI for each
target that use it in their config/whatever file...? Is it a way to go?

I can't attach this function to run_cleanup_chain, because I need to
call cleanup_cfi() before objfile_purge_solibs() and also because
do_run_cleanups() finally destroys the contents of run_cleanup_chain and
finally because I don't know how (when/where) to attach cleanup_cfi() to
run_cleanup_chain.

Could someone please tell me what is the cleanest way to call
cleanup_cfi()? Thanks.

Michal Ludvig
--
* SuSE CR, s.r.o * mludvig@suse.cz
* (+420) 296.545.373 * http://www.suse.cz

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Index: dwarf2cfi.h
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2cfi.c,v
retrieving revision 1.16
diff -u -p -r1.16 dwarf2cfi.h
--- dwarf2cfi.h 19 Jul 2002 09:40:51 -0000 1.16
+++ dwarf2cfi.h 20 Dec 2002 15:14:21 -0000
@@ -64,6 +64,12 @@ struct cie_unit

/* Next in chain. */
struct cie_unit *next;
+
+ /* Keep or destroy this CIE on a new run? */
+ int keep;
+
+ /* How many FDEs refer to this CIE? */
+ int refs;
};

/* Frame Description Entry. */
Index: dwarf2cfi.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2cfi.c,v
retrieving revision 1.16
diff -u -p -r1.16 dwarf2cfi.c
--- dwarf2cfi.c 19 Jul 2002 09:40:51 -0000 1.16
+++ dwarf2cfi.c 20 Dec 2002 15:14:21 -0000
@@ -317,6 +326,86 @@ frame_state_alloc (void)
(struct frame_state_reg *) obstack_alloc (&unwind_tmp_obstack, regs_size);
memset (fs->regs.reg, 0, regs_size);
return fs;
+}
+
+void
+cleanup_cfi (void *name)
+{
+ struct objfile *ofp;
+ struct cie_unit *cie, *cie_prev;
+ int fde_index=0, fde_free=0;
+
+ cie = cie_chunks;
+ while (cie)
+ {
+ cie->refs = 0;
+ cie->keep = 0;
+ cie = cie->next;
+ }
+
+ /* Mark all unwanted CIEs. */
+ ALL_OBJFILES (ofp)
+ {
+ if (!(ofp->flags & OBJF_USERLOADED) && (ofp->flags & OBJF_SHARED))
+ printf ("\tRemoving %s...\n", ofp->name);
+ else
+ {
+ printf ("\tKeeping %s...\n", ofp->name);
+ cie = cie_chunks;
+ while(cie)
+ {
+ if (cie->objfile == ofp)
+ cie->keep = 1;
+ cie = cie->next;
+ }
+ }
+ }
+
+ /* Remove all FDEs pointing to unwanted CIEs. */
+ for (fde_index = 0, fde_free=0;
+ fde_index < fde_chunks.elems;
+ fde_index++, fde_free++)
+ {
+ if (!fde_chunks.array[fde_index]->cie_ptr->keep)
+ {
+ fde_free--;
+ continue;
+ }
+ else if (fde_free < fde_index)
+ fde_chunks.array[fde_free] = fde_chunks.array[fde_index];
+ fde_chunks.array[fde_free]->cie_ptr->refs++;
+ }
+ fde_chunks.elems = fde_free;
+
+ /* Remove all unwanted CIEs. */
+ cie = cie_chunks;
+ cie_prev = NULL;
+ while (cie)
+ {
+ struct cie_unit *cie_tmp;
+
+ if (! cie->keep || !cie->refs)
+ {
+ cie_tmp = cie;
+ if (cie_prev == NULL)
+ {
+ cie_chunks = cie->next;
+ cie = cie_chunks;
+ }
+ else
+ {
+ cie_prev->next = cie->next;
+ cie = cie->next;
+ }
+ /* cie_prev must remain unchanged. */
+ xfree (cie_tmp);
+ }
+ else
+ {
+ cie_prev = cie;
+ cie = cie->next;
+ }
+ }
}

static void