[PATCH v4 1/4] gdb, dwarf: add support for DW_AT_trampoline in DWARF reader
Abdul Basit Ijaz
abdul.b.ijaz@intel.com
Tue Aug 1 22:47:41 GMT 2023
From: Nils-Christian Kempke <nils-christian.kempke@intel.com>
DW_AT_trampoline can be used to describe compiler generated functions
that serve some intermediary purpose on making a call to another
function. A compiler can emit this tag in order to help a debugger hide
the trampolines from a user.
The attribute is only applicable to DW_TAG_subroutine and
DW_TAG_inlined_subroutine tags. It contains information about the
trampoline target either as a reference to its DIE, as its address or
its name. DW_AT_trampoline can also be a flag indicating that the DIE
is a trampoline or not without specifying the target (e.g. if it is
unknown).
This patch adds support to GDB for reading the DW_AT_trampoline
attribute. It stores the attribute and its value in the type_specific
part of a GDB type. This patch is implemented in preparation of the
following patches, which will add a mechanism to hide DW_AT_trampoline
subroutines from the user.
2023-08-01 Nils-Christian Kempke <nils-christian.kempke@intel.com>
---
gdb/dwarf2/read.c | 49 +++++++++++++++++++-
gdb/gdbtypes.c | 34 +++++++++++++-
gdb/gdbtypes.h | 113 ++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 189 insertions(+), 7 deletions(-)
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index b1f1c1d7257..56407c618d2 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -14657,6 +14657,53 @@ read_subroutine_type (struct die_info *die, struct dwarf2_cu *cu)
if (prototyped_function_p (die, cu))
ftype->set_is_prototyped (true);
+ /* If this is a trampoline function store it and its target here. */
+ attr = dwarf2_attr (die, DW_AT_trampoline, cu);
+ if (attr != nullptr)
+ {
+ TYPE_FUNC_FLAGS (ftype) |= FUNC_TYPE_TRAMPOLINE;
+ TYPE_TRAMPOLINE_TARGET (ftype)
+ = (trampoline_target *) TYPE_ZALLOC (ftype,
+ sizeof (trampoline_target));
+
+ /* A DW_AT_trampoline can be either an address, a flag, a reference or a
+ string. */
+ if (attr->form_is_string ())
+ TYPE_TRAMPOLINE_TARGET (ftype)->set_target_name
+ (attr->as_string ());
+ else if (attr->form_is_ref ())
+ {
+ die_info *target_die;
+ dwarf2_cu *target_cu = cu;
+
+ target_die = follow_die_ref (die, attr, &target_cu);
+ const char *target_name;
+ /* Prefer the mangled name; otherwise compute the demangled one. */
+ target_name = dw2_linkage_name (target_die, target_cu);
+ if (target_name == NULL)
+ target_name = dwarf2_physname (NULL, target_die, target_cu);
+ if (target_name == nullptr)
+ {
+ complaint (_("DW_AT_trampoline target DIE has no name for"
+ "referencing DIE %s [in module %s]"),
+ sect_offset_str (die->sect_off),
+ objfile_name (objfile));
+ }
+ TYPE_TRAMPOLINE_TARGET (ftype)->set_target_name (target_name);
+ }
+ else if (attr->form_is_unsigned ())
+ TYPE_TRAMPOLINE_TARGET (ftype)->set_target_flag (attr->as_boolean ());
+ else
+ {
+ unrelocated_addr target_addr_reloc = attr->as_address ();
+ CORE_ADDR target_addr
+ = cu->per_objfile->relocate (target_addr_reloc);
+ target_addr = gdbarch_adjust_dwarf2_addr (objfile->arch (),
+ target_addr);
+ TYPE_TRAMPOLINE_TARGET (ftype)->set_target_physaddr (target_addr);
+ }
+ }
+
/* Store the calling convention in the type if it's available in
the subroutine die. Otherwise set the calling convention to
the default value DW_CC_normal. */
@@ -14674,7 +14721,7 @@ read_subroutine_type (struct die_info *die, struct dwarf2_cu *cu)
if the DWARF producer set that information. */
attr = dwarf2_attr (die, DW_AT_noreturn, cu);
if (attr && attr->as_boolean ())
- TYPE_NO_RETURN (ftype) = 1;
+ TYPE_FUNC_FLAGS (ftype) |= FUNC_TYPE_NO_RETURN;
/* We need to add the subroutine type to the die immediately so
we don't infinitely recurse when dealing with parameters
diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
index c5272979cb9..6d25cdc944e 100644
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -5091,6 +5091,33 @@ print_fixed_point_type_info (struct type *type, int spaces)
type->fixed_point_scaling_factor ().str ().c_str ());
}
+/* Print the contents of the TYPE's self_trampoline_target, assuming that its
+ type-specific kind is TYPE_SPECIFIC_FUNC and is_trampoline is not 0. */
+static void
+print_trampoline_target_info (struct type *type, int spaces)
+{
+ switch (TYPE_TRAMPOLINE_TARGET (type)->target_kind ())
+ {
+ case TRAMPOLINE_TARGET_PHYSADDR:
+ gdb_printf ("%*starget physaddr: 0x%s\n", spaces + 2, "",
+ print_core_address (type->arch_owner (),
+ TYPE_TRAMPOLINE_TARGET (type)
+ ->target_physaddr ()));
+ break;
+ case TRAMPOLINE_TARGET_NAME:
+ gdb_printf ("%*starget name: %s\n", spaces + 2, "",
+ TYPE_TRAMPOLINE_TARGET (type)->target_name ());
+ break;
+ case TRAMPOLINE_TARGET_FLAG:
+ gdb_printf ("%*starget flag: %d\n", spaces + 2, "",
+ TYPE_TRAMPOLINE_TARGET (type)->target_flag ());
+ break;
+ default:
+ gdb_assert_not_reached ("unhandled trampoline target kind");
+ break;
+ }
+}
+
static struct obstack dont_print_type_obstack;
/* Print the dynamic_prop PROP. */
@@ -5417,6 +5444,10 @@ recursive_dump_type (struct type *type, int spaces)
gdb_printf ("%*scalling_convention %d\n", spaces, "",
TYPE_CALLING_CONVENTION (type));
/* tail_call_list is not printed. */
+ gdb_printf ("%*sfunc_type_flags %u\n", spaces, "",
+ (unsigned int) TYPE_FUNC_FLAGS (type));
+ if (TYPE_IS_TRAMPOLINE (type))
+ print_trampoline_target_info (type, spaces);
break;
case TYPE_SPECIFIC_SELF_TYPE:
@@ -5633,8 +5664,9 @@ copy_type_recursive (struct type *type, htab_t copied_types)
case TYPE_SPECIFIC_FUNC:
INIT_FUNC_SPECIFIC (new_type);
TYPE_CALLING_CONVENTION (new_type) = TYPE_CALLING_CONVENTION (type);
- TYPE_NO_RETURN (new_type) = TYPE_NO_RETURN (type);
+ TYPE_FUNC_FLAGS (new_type) = TYPE_FUNC_FLAGS (type);
TYPE_TAIL_CALL_LIST (new_type) = NULL;
+ TYPE_TRAMPOLINE_TARGET (new_type) = TYPE_TRAMPOLINE_TARGET (type);
break;
case TYPE_SPECIFIC_FLOATFORMAT:
TYPE_FLOATFORMAT (new_type) = TYPE_FLOATFORMAT (type);
diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h
index aedaf53cd5d..310d00d0230 100644
--- a/gdb/gdbtypes.h
+++ b/gdb/gdbtypes.h
@@ -106,6 +106,21 @@ enum type_instance_flag_value : unsigned
DEF_ENUM_FLAGS_TYPE (enum type_instance_flag_value, type_instance_flags);
+/* * Define flags for function types. */
+enum func_type_flag_value : unsigned
+{
+ /* * Flag indicates, whether this function normally returns to its
+ caller. It is set from the DW_AT_noreturn attribute if set on
+ the DW_TAG_subprogram. */
+ FUNC_TYPE_NO_RETURN = (1 << 0),
+
+ /* * Flag is used for functions marked with DW_AT_trampoline. These
+ are compiler generated wrappers that should be hidden from the user. */
+ FUNC_TYPE_TRAMPOLINE = (1 << 1)
+};
+
+DEF_ENUM_FLAGS_TYPE (enum func_type_flag_value, func_type_flags);
+
/* * Not textual. By default, GDB treats all single byte integers as
characters (or elements of strings) unless this flag is set. */
@@ -1730,11 +1745,9 @@ struct func_type
ENUM_BITFIELD (dwarf_calling_convention) calling_convention : 8;
- /* * Whether this function normally returns to its caller. It is
- set from the DW_AT_noreturn attribute if set on the
- DW_TAG_subprogram. */
+ /* * For storing function types defined in eunm func_type_flag_value. */
- unsigned int is_noreturn : 1;
+ func_type_flags flags;
/* * Only those DW_TAG_call_site's in this function that have
DW_AT_call_tail_call set are linked in this list. Function
@@ -1749,6 +1762,87 @@ struct func_type
contains the method. */
struct type *self_type;
+
+ struct trampoline_target *self_trampoline_target;
+ };
+
+/* The kind of location held by this call site target. */
+enum trampoline_target_kind
+ {
+ /* An address. */
+ TRAMPOLINE_TARGET_PHYSADDR,
+ /* A (mangled) name. */
+ TRAMPOLINE_TARGET_NAME,
+ /* An flag (target is unknown). */
+ TRAMPOLINE_TARGET_FLAG,
+ };
+
+/* Target information for trampoline functions. */
+
+struct trampoline_target
+ {
+ /* Returns what kind of target the trampoline points to. */
+ trampoline_target_kind target_kind () const
+ {
+ return m_target_kind;
+ }
+
+ /* Set the address for trampoline target. */
+ void set_target_physaddr (CORE_ADDR physaddr)
+ {
+ m_target_kind = TRAMPOLINE_TARGET_PHYSADDR;
+ m_trampoline_target.physaddr = physaddr;
+ }
+
+ /* Return the address of the trampoline target. */
+ CORE_ADDR target_physaddr () const
+ {
+ gdb_assert (m_target_kind == TRAMPOLINE_TARGET_PHYSADDR);
+ return m_trampoline_target.physaddr;
+ }
+
+ /* Set the name of the trampoline target. */
+ void set_target_name (const char *name)
+ {
+ m_target_kind = TRAMPOLINE_TARGET_NAME;
+ m_trampoline_target.name = name;
+ }
+
+ /* Return the name of the trampoline target. */
+ const char *target_name () const
+ {
+ gdb_assert (m_target_kind == TRAMPOLINE_TARGET_NAME);
+ return m_trampoline_target.name;
+ }
+
+ /* Set the flag for trampoline target subroutine. */
+ void set_target_flag (bool flag)
+ {
+ m_target_kind = TRAMPOLINE_TARGET_FLAG;
+ m_trampoline_target.flag = flag;
+ }
+
+ /* Return the flag for trampoline target. */
+ bool target_flag () const
+ {
+ gdb_assert (m_target_kind == TRAMPOLINE_TARGET_FLAG);
+ return m_trampoline_target.flag;
+ }
+
+ private:
+
+ union
+ {
+ /* Address. */
+ CORE_ADDR physaddr;
+ /* Mangled name. */
+ const char *name;
+ /* Flag. */
+ bool flag;
+ } m_trampoline_target;
+
+ /* * Discriminant for union m_trampoline_target. */
+ ENUM_BITFIELD (trampoline_target_kind) m_target_kind : 2;
};
/* The type-specific info for TYPE_CODE_FIXED_POINT types. */
@@ -1891,7 +1985,16 @@ extern void set_type_vptr_basetype (struct type *, struct type *);
#define TYPE_GNAT_SPECIFIC(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.gnat_stuff
#define TYPE_DESCRIPTIVE_TYPE(thistype) TYPE_GNAT_SPECIFIC(thistype)->descriptive_type
#define TYPE_CALLING_CONVENTION(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->calling_convention
-#define TYPE_NO_RETURN(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->is_noreturn
+#define TYPE_FUNC_FLAGS(thistype) \
+ TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->flags
+#define TYPE_NO_RETURN(thistype) \
+ (TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->flags \
+ & FUNC_TYPE_NO_RETURN)
+#define TYPE_IS_TRAMPOLINE(thistype) \
+ (TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->flags \
+ & FUNC_TYPE_TRAMPOLINE)
+#define TYPE_TRAMPOLINE_TARGET(thistype) \
+ TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->self_trampoline_target
#define TYPE_TAIL_CALL_LIST(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->tail_call_list
#define TYPE_BASECLASS(thistype,index) ((thistype)->field (index).type ())
#define TYPE_N_BASECLASSES(thistype) TYPE_CPLUS_SPECIFIC(thistype)->n_baseclasses
--
2.34.1
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