Re: Dwarf-2 unwinding vs. manual prologue analysis

Orjan Friberg
2005-05-27T14:38:33Z

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(Back to gdb-patches@ for patch submission.)

Orjan Friberg wrote:
>
> Ah, now I see. The things that broke without any prologue scanning were
> indeed things like 'next' over library calls (PLT stubs) and things
> related to call dummys (callfuncs.exp).

Add signal trampolines to that list too.

The change below (committed) doesn't make anything better or worse; it just
clarifies the situation in which it's assumed that the new CRISv32-specific
prologue scanner will be used and what conditions are assumed to hold true.

2005-05-27 Orjan Friberg <orjanf@axis.com>

* cris-tdep.c (crisv32_scan_prologue): Add.
(cris_frame_unwind_cache, cris_skip_prologue): Call
crisv32_scan_prologue when debugging CRISv32.

--
Orjan Friberg
Axis Communications

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Index: cris-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/cris-tdep.c,v
retrieving revision 1.131
diff -u -p -r1.131 cris-tdep.c
--- cris-tdep.c 27 May 2005 13:47:59 -0000 1.131
+++ cris-tdep.c 27 May 2005 14:14:24 -0000
@@ -724,6 +724,10 @@ static CORE_ADDR cris_scan_prologue (COR
struct frame_info *next_frame,
struct cris_unwind_cache *info);

+static CORE_ADDR crisv32_scan_prologue (CORE_ADDR pc,
+ struct frame_info *next_frame,
+ struct cris_unwind_cache *info);
+
static CORE_ADDR cris_unwind_pc (struct gdbarch *gdbarch,
struct frame_info *next_frame);

@@ -795,7 +799,10 @@ cris_frame_unwind_cache (struct frame_in
info->leaf_function = 0;

/* Prologue analysis does the rest... */
- cris_scan_prologue (frame_func_unwind (next_frame), next_frame, info);
+ if (cris_version () == 32)
+ crisv32_scan_prologue (frame_func_unwind (next_frame), next_frame, info);
+ else
+ cris_scan_prologue (frame_func_unwind (next_frame), next_frame, info);

return info;
}
@@ -1375,6 +1382,42 @@ cris_scan_prologue (CORE_ADDR pc, struct
return pc;
}

+static CORE_ADDR
+crisv32_scan_prologue (CORE_ADDR pc, struct frame_info *next_frame,
+ struct cris_unwind_cache *info)
+{
+ ULONGEST this_base;
+
+ /* Unlike the CRISv10 prologue scanner (cris_scan_prologue), this is not
+ meant to be a full-fledged prologue scanner. It is only needed for
+ the cases where we end up in code always lacking DWARF-2 CFI, notably:
+
+ * PLT stubs (library calls)
+ * call dummys
+ * signal trampolines
+
+ For those cases, it is assumed that there is no actual prologue; that
+ the stack pointer is not adjusted, and (as a consequence) the return
+ address is not pushed onto the stack. */
+
+ /* We only want to know the end of the prologue when next_frame and info
+ are NULL (called from cris_skip_prologue i.e.). */
+ if (next_frame == NULL && info == NULL)
+ {
+ return pc;
+ }
+
+ /* The SP is assumed to be unaltered. */
+ frame_unwind_unsigned_register (next_frame, SP_REGNUM, &this_base);
+ info->base = this_base;
+ info->prev_sp = this_base;
+
+ /* The PC is assumed to be found in SRP. */
+ info->saved_regs[PC_REGNUM] = info->saved_regs[SRP_REGNUM];
+
+ return pc;
+}
+
/* Advance pc beyond any function entry prologue instructions at pc
to reach some "real" code. */

@@ -1397,7 +1440,11 @@ cris_skip_prologue (CORE_ADDR pc)
return sal.end;
}

- pc_after_prologue = cris_scan_prologue (pc, NULL, NULL);
+ if (cris_version () == 32)
+ pc_after_prologue = crisv32_scan_prologue (pc, NULL, NULL);
+ else
+ pc_after_prologue = cris_scan_prologue (pc, NULL, NULL);
+
return pc_after_prologue;
}