[rfc] [11/18] Cell multi-arch: Target description infrastructure

Ulrich Weigand
2008-09-07T21:15:52Z

Hello,

this patch extends the target description infrastructure to allow a target
to define "compatible" architectures. This is used to specify e.g. on Cell
that even though the target is PowerPC, it is compatible with executables
of the SPU architecture -- in an inferior process of PowerPC architecture,
objfiles of SPU architecture may be present as shared libraries or even
the main executable.

This is primarily required to prevent choose_architecture_for_target from
rejecting a target description of architecture PowerPC just because a main
executable of architecture SPU was just started.

It is also a convenient means to inquire whether the current target is
a Cell system (as opposed to a regular PowerPC).

Bye,
Ulrich

ChangeLog:

* target-descriptions.h (tdesc_compatible_p): New.
(tdesc_add_compatible): New.
* target-descriptions.c (arch_p): New VEC_P type.
(struct target_desc): New member compatible.
(free_target_description): Handle it.
(maint_print_c_tdesc_cmd): Likewise.
(tdesc_compatible_p): New function.
(tdesc_add_compatible): New function.

* xml-tdesc.c (tdesc_end_compatible): New function.
(target_children): Handle <compatible> element.

* arch-utils.c (choose_architecture_for_target): Accept target
description instead of BFD architecture as input. Query target
description for compatible architectures.
(gdbarch_info_fill): Update call.

doc/ChangeLog:

* gdb.texinfo (Target Descriptions): Document <compatible> element.

Index: src/gdb/arch-utils.c
===================================================================
--- src.orig/gdb/arch-utils.c
+++ src/gdb/arch-utils.c
@@ -326,15 +326,24 @@ set_endian (char *ignore_args, int from_
}

/* Given SELECTED, a currently selected BFD architecture, and
- FROM_TARGET, a BFD architecture reported by the target description,
- return what architecture to use. Either may be NULL; if both are
- specified, we use the more specific. If the two are obviously
- incompatible, warn the user. */
+ TARGET_DESC, the current target description, return what
+ architecture to use.
+
+ SELECTED may be NULL, in which case we return the architecture
+ associated with TARGET_DESC. If SELECTED specifies a variant
+ of the architecture associtated with TARGET_DESC, return the
+ more specific of the two.
+
+ If SELECTED is a different architecture, but it is accepted as
+ compatible by the target, we can use the target architecture.
+
+ If SELECTED is obviously incompatible, warn the user. */

static const struct bfd_arch_info *
-choose_architecture_for_target (const struct bfd_arch_info *selected,
- const struct bfd_arch_info *from_target)
+choose_architecture_for_target (const struct target_desc *target_desc,
+ const struct bfd_arch_info *selected)
{
+ const struct bfd_arch_info *from_target = tdesc_architecture (target_desc);
const struct bfd_arch_info *compat1, *compat2;

if (selected == NULL)
@@ -364,6 +373,11 @@ choose_architecture_for_target (const st

if (compat1 == NULL && compat2 == NULL)
{
+ /* BFD considers the architectures incompatible. Check our target
+ description whether it accepts SELECTED as compatible anyway. */
+ if (tdesc_compatible_p (target_desc, selected))
+ return from_target;
+
warning (_("Selected architecture %s is not compatible "
"with reported target architecture %s"),
selected->printable_name, from_target->printable_name);
@@ -692,7 +706,7 @@ gdbarch_info_fill (struct gdbarch_info *
/* From the target. */
if (info->target_desc != NULL)
info->bfd_arch_info = choose_architecture_for_target
- (info->bfd_arch_info, tdesc_architecture (info->target_desc));
+ (info->target_desc, info->bfd_arch_info);
/* From the default. */
if (info->bfd_arch_info == NULL)
info->bfd_arch_info = default_bfd_arch;
Index: src/gdb/target-descriptions.c
===================================================================
--- src.orig/gdb/target-descriptions.c
+++ src/gdb/target-descriptions.c
@@ -104,6 +104,10 @@ typedef struct tdesc_feature
} *tdesc_feature_p;
DEF_VEC_P(tdesc_feature_p);

+/* A compatible architecture from a target description. */
+typedef const struct bfd_arch_info *arch_p;
+DEF_VEC_P(arch_p);
+
/* A target description. */

struct target_desc
@@ -111,6 +115,9 @@ struct target_desc
/* The architecture reported by the target, if any. */
const struct bfd_arch_info *arch;

+ /* The list of compatible architectures reported by the target. */
+ VEC(arch_p) *compatible;
+
/* Any architecture-specific properties specified by the target. */
VEC(property_s) *properties;

@@ -290,6 +297,28 @@ tdesc_architecture (const struct target_
{
return target_desc->arch;
}
+
+/* Return non-zero if this target description is compatible
+ with the given BFD architecture. */
+
+int
+tdesc_compatible_p (const struct target_desc *target_desc,
+ const struct bfd_arch_info *arch)
+{
+ const struct bfd_arch_info *compat;
+ int ix;
+
+ for (ix = 0; VEC_iterate (arch_p, target_desc->compatible, ix, compat);
+ ix++)
+ {
+ if (compat == arch
+ || arch->compatible (arch, compat)
+ || compat->compatible (compat, arch))
+ return 1;
+ }
+
+ return 0;
+}
\f

/* Return 1 if this target description includes any registers. */
@@ -885,6 +914,8 @@ free_target_description (void *arg)
}
VEC_free (property_s, target_desc->properties);

+ VEC_free (arch_p, target_desc->compatible);
+
xfree (target_desc);
}

@@ -895,6 +926,30 @@ make_cleanup_free_target_description (st
}

void
+tdesc_add_compatible (struct target_desc *target_desc,
+ const struct bfd_arch_info *compatible)
+{
+ const struct bfd_arch_info *compat;
+ int ix;
+
+ /* If this instance of GDB is compiled without BFD support for the
+ compatible architecture, simply ignore it -- we would not be able
+ to handle it anyway. */
+ if (compatible == NULL)
+ return;
+
+ for (ix = 0; VEC_iterate (arch_p, target_desc->compatible, ix, compat);
+ ix++)
+ if (compat == compatible)
+ internal_error (__FILE__, __LINE__,
+ _("Attempted to add duplicate "
+ "compatible architecture \"%s\""),
+ compatible->printable_name);
+
+ VEC_safe_push (arch_p, target_desc->compatible, compatible);
+}
+
+void
set_tdesc_property (struct target_desc *target_desc,
const char *key, const char *value)
{
@@ -993,6 +1048,7 @@ static void
maint_print_c_tdesc_cmd (char *args, int from_tty)
{
const struct target_desc *tdesc;
+ const struct bfd_arch_info *compatible;
const char *filename, *inp;
char *function, *outp;
struct property *prop;
@@ -1049,6 +1105,16 @@ maint_print_c_tdesc_cmd (char *args, int
printf_unfiltered ("\n");
}

+ for (ix = 0; VEC_iterate (arch_p, tdesc->compatible, ix, compatible);
+ ix++)
+ {
+ printf_unfiltered
+ (" tdesc_add_compatible (result, bfd_scan_arch (\"%s\"));\n",
+ compatible->printable_name);
+ }
+ if (ix)
+ printf_unfiltered ("\n");
+
for (ix = 0; VEC_iterate (property_s, tdesc->properties, ix, prop);
ix++)
{
Index: src/gdb/target-descriptions.h
===================================================================
--- src.orig/gdb/target-descriptions.h
+++ src/gdb/target-descriptions.h
@@ -123,6 +123,12 @@ int tdesc_numbered_register_choices (con
const struct bfd_arch_info *tdesc_architecture
(const struct target_desc *);

+/* Return non-zero if this target description is compatible
+ with the given BFD architecture. */
+
+int tdesc_compatible_p (const struct target_desc *,
+ const struct bfd_arch_info *);
+
/* Return the string value of a property named KEY, or NULL if the
property was not specified. */

@@ -169,6 +175,8 @@ void set_tdesc_architecture (struct targ
const struct bfd_arch_info *);
void set_tdesc_property (struct target_desc *,
const char *key, const char *value);
+void tdesc_add_compatible (struct target_desc *,
+ const struct bfd_arch_info *);

struct tdesc_feature *tdesc_create_feature (struct target_desc *tdesc,
const char *name);
Index: src/gdb/xml-tdesc.c
===================================================================
--- src.orig/gdb/xml-tdesc.c
+++ src/gdb/xml-tdesc.c
@@ -106,6 +106,20 @@ tdesc_end_arch (struct gdb_xml_parser *p
set_tdesc_architecture (data->tdesc, arch);
}

+/* Handle the end of a <compatible> element and its value. */
+
+static void
+tdesc_end_compatible (struct gdb_xml_parser *parser,
+ const struct gdb_xml_element *element,
+ void *user_data, const char *body_text)
+{
+ struct tdesc_parsing_data *data = user_data;
+ const struct bfd_arch_info *arch;
+
+ arch = bfd_scan_arch (body_text);
+ tdesc_add_compatible (data->tdesc, arch);
+}
+
/* Handle the start of a <target> element. */

static void
@@ -345,6 +359,8 @@ static const struct gdb_xml_attribute ta
static const struct gdb_xml_element target_children[] = {
{ "architecture", NULL, NULL, GDB_XML_EF_OPTIONAL,
NULL, tdesc_end_arch },
+ { "compatible", NULL, NULL, GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
+ NULL, tdesc_end_compatible },
{ "feature", feature_attributes, feature_children,
GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
tdesc_start_feature, NULL },
Index: src/gdb/doc/gdb.texinfo
===================================================================
--- src.orig/gdb/doc/gdb.texinfo
+++ src/gdb/doc/gdb.texinfo
@@ -27586,6 +27586,7 @@ are explained further below.

<target version="1.0">
@r{[}@var{architecture}@r{]}
+ @r{[}@var{compatible}@dots{}@r{]}
@r{[}@var{feature}@dots{}@r{]}
</target>
@end smallexample
@@ -27641,6 +27642,26 @@ An @samp{<architecture>} element has thi
accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
Debugging Target}).

+@subsection Compatible Architecture
+@cindex <compatible>
+
+A @samp{<compatible>} element has this form:
+
+@smallexample
+ <compatible>@var{arch}</compatible>
+@end smallexample
+
+@var{arch} is an architecture name from the same selection
+accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
+Debugging Target}).
+
+A @samp{<compatible>} element is used to specify that the target
+is able to run binaries in some other than the main target architecture
+given by the @samp{<architecture>} element. For example, on the
+Cell Broadband Engine, the main architecture is @code{powerpc:common}
+or @code{powerpc:common64}, but the system is able to run binaries
+in the @code{spu} architecture as well.