Re: [PATCH/RFC] Per-architecture DWARF CFI register state initialization hooks

Mark Kettenis
2004-02-15T21:31:22Z

Thanks for the info. Based on what you wrote, I committed the
attached patch. It should now be possible to integrate the IBM S/390
and zSeries stuff.

Mark

Index: ChangeLog
from Mark Kettenis <kettenis@gnu.org>

* dwarf2-frame.h (dwarf2_frame_set_init_reg): New prototype.
* dwarf2-frame.c (dwarf2_frame_data): New variable.
(struct dwarf2_frame_ops): New.
(dwarf2_frame_default_init_reg): New function, based on
dwarf2_frame_init_reg.
(dwarf2_frame_init, dwarf2_frame_set_init_reg): New function.
(dwarf2_frame_init_reg): Call architecture-specific function.
(dwarf2_frame_objfile_data): Renamed from dwarf2_frame_data.
(dwarf2_frame_find_fde, add_fde): Use dwarf2_frame_objfile_data
instead of dwarf2_frame_data.
(_initialize_dwarf2_frame): Initailize new dwarf2_frame_data.
Initialize dwarf2_frame_objfile instead of old dwarf2_frame_data.

Index: dwarf2-frame.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2-frame.c,v
retrieving revision 1.29
diff -u -p -r1.29 dwarf2-frame.c
--- dwarf2-frame.c 7 Feb 2004 18:29:53 -0000 1.29
+++ dwarf2-frame.c 15 Feb 2004 21:27:19 -0000
@@ -454,53 +454,107 @@ execute_cfa_program (unsigned char *insn
dwarf2_frame_state_free_regs (fs->regs.prev);
fs->regs.prev = NULL;
}
+\f

-struct dwarf2_frame_cache
-{
- /* DWARF Call Frame Address. */
- CORE_ADDR cfa;
+/* Architecture-specific operations. */

- /* Saved registers, indexed by GDB register number, not by DWARF
- register number. */
- struct dwarf2_frame_state_reg *reg;
+/* Per-architecture data key. */
+static struct gdbarch_data *dwarf2_frame_data;
+
+struct dwarf2_frame_ops
+{
+ /* Pre-initialize the register state REG for register REGNUM. */
+ void (*init_reg) (struct gdbarch *, int, struct dwarf2_frame_state_reg *);
};

-/* Initialize the register state REG. If we have a register that acts
- as a program counter, mark it as a destination for the return
- address. If we have a register that serves as the stack pointer,
- arrange for it to be filled with the call frame address (CFA). The
- other registers are marked as unspecified.
-
- We copy the return address to the program counter, since many parts
- in GDB assume that it is possible to get the return address by
- unwind the program counter register. However, on ISA's with a
- dedicated return address register, the CFI usually only contains
- information to unwind that return address register.
-
- The reason we're treating the stack pointer special here is because
- in many cases GCC doesn't emit CFI for the stack pointer and
- implicitly assumes that it is equal to the CFA. This makes some
- sense since the DWARF specification (version 3, draft 8, p. 102)
- says that:
-
- "Typically, the CFA is defined to be the value of the stack pointer
- at the call site in the previous frame (which may be different from
- its value on entry to the current frame)."
-
- However, this isn't true for all platforms supported by GCC
- (e.g. IBM S/390 and zSeries). For those targets we should override
- the defaults given here. */
+/* Default architecture-specific register state initialization
+ function. */

static void
-dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
- struct dwarf2_frame_state_reg *reg)
+dwarf2_frame_default_init_reg (struct gdbarch *gdbarch, int regnum,
+ struct dwarf2_frame_state_reg *reg)
{
+ /* If we have a register that acts as a program counter, mark it as
+ a destination for the return address. If we have a register that
+ serves as the stack pointer, arrange for it to be filled with the
+ call frame address (CFA). The other registers are marked as
+ unspecified.
+
+ We copy the return address to the program counter, since many
+ parts in GDB assume that it is possible to get the return address
+ by unwinding the program counter register. However, on ISA's
+ with a dedicated return address register, the CFI usually only
+ contains information to unwind that return address register.
+
+ The reason we're treating the stack pointer special here is
+ because in many cases GCC doesn't emit CFI for the stack pointer
+ and implicitly assumes that it is equal to the CFA. This makes
+ some sense since the DWARF specification (version 3, draft 8,
+ p. 102) says that:
+
+ "Typically, the CFA is defined to be the value of the stack
+ pointer at the call site in the previous frame (which may be
+ different from its value on entry to the current frame)."
+
+ However, this isn't true for all platforms supported by GCC
+ (e.g. IBM S/390 and zSeries). Those architectures should provide
+ their own architecture-specific initialization function. */
+
if (regnum == PC_REGNUM)
reg->how = DWARF2_FRAME_REG_RA;
else if (regnum == SP_REGNUM)
reg->how = DWARF2_FRAME_REG_CFA;
}

+/* Return a default for the architecture-specific operations. */
+
+static void *
+dwarf2_frame_init (struct gdbarch *gdbarch)
+{
+ struct dwarf2_frame_ops *ops;
+
+ ops = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct dwarf2_frame_ops);
+ ops->init_reg = dwarf2_frame_default_init_reg;
+ return ops;
+}
+
+/* Set the architecture-specific register state initialization
+ function for GDBARCH to INIT_REG. */
+
+void
+dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
+ void (*init_reg) (struct gdbarch *, int,
+ struct dwarf2_frame_state_reg *))
+{
+ struct dwarf2_frame_ops *ops;
+
+ ops = gdbarch_data (gdbarch, dwarf2_frame_data);
+ ops->init_reg = init_reg;
+}
+
+/* Pre-initialize the register state REG for register REGNUM. */
+
+static void
+dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
+ struct dwarf2_frame_state_reg *reg)
+{
+ struct dwarf2_frame_ops *ops;
+
+ ops = gdbarch_data (gdbarch, dwarf2_frame_data);
+ ops->init_reg (gdbarch, regnum, reg);
+}
+\f
+
+struct dwarf2_frame_cache
+{
+ /* DWARF Call Frame Address. */
+ CORE_ADDR cfa;
+
+ /* Saved registers, indexed by GDB register number, not by DWARF
+ register number. */
+ struct dwarf2_frame_state_reg *reg;
+};
+
static struct dwarf2_frame_cache *
dwarf2_frame_cache (struct frame_info *next_frame, void **this_cache)
{
@@ -851,7 +905,7 @@ struct comp_unit
bfd_vma tbase;
};

-const struct objfile_data *dwarf2_frame_data;
+const struct objfile_data *dwarf2_frame_objfile_data;

static unsigned int
read_1_byte (bfd *bfd, char *buf)
@@ -1111,7 +1165,7 @@ dwarf2_frame_find_fde (CORE_ADDR *pc)
struct dwarf2_fde *fde;
CORE_ADDR offset;

- fde = objfile_data (objfile, dwarf2_frame_data);
+ fde = objfile_data (objfile, dwarf2_frame_objfile_data);
if (fde == NULL)
continue;

@@ -1137,8 +1191,8 @@ dwarf2_frame_find_fde (CORE_ADDR *pc)
static void
add_fde (struct comp_unit *unit, struct dwarf2_fde *fde)
{
- fde->next = objfile_data (unit->objfile, dwarf2_frame_data);
- set_objfile_data (unit->objfile, dwarf2_frame_data, fde);
+ fde->next = objfile_data (unit->objfile, dwarf2_frame_objfile_data);
+ set_objfile_data (unit->objfile, dwarf2_frame_objfile_data, fde);
}

#ifdef CC_HAS_LONG_LONG
@@ -1461,7 +1515,6 @@ decode_frame_entry (struct comp_unit *un

return ret;
}
-
\f

/* FIXME: kettenis/20030504: This still needs to be integrated with
@@ -1541,5 +1594,6 @@ void _initialize_dwarf2_frame (void);
void
_initialize_dwarf2_frame (void)
{
- dwarf2_frame_data = register_objfile_data ();
+ dwarf2_frame_data = register_gdbarch_data (dwarf2_frame_init);
+ dwarf2_frame_objfile_data = register_objfile_data ();
}
Index: dwarf2-frame.h
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2-frame.h,v
retrieving revision 1.4
diff -u -p -r1.4 dwarf2-frame.h
--- dwarf2-frame.h 7 Feb 2004 14:44:50 -0000 1.4
+++ dwarf2-frame.h 15 Feb 2004 21:27:19 -0000
@@ -71,6 +71,13 @@ struct dwarf2_frame_state_reg
enum dwarf2_frame_reg_rule how;
};

+/* Set the architecture-specific register state initialization
+ function for GDBARCH to INIT_REG. */
+
+extern void dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
+ void (*init_reg) (struct gdbarch *, int,
+ struct dwarf2_frame_state_reg *));
+
/* Return the frame unwind methods for the function that contains PC,
or NULL if it can't be handled by DWARF CFI frame unwinder. */