[PATCH v3 0/2] gdb: Fix internal inferior calls through GNU IFUNCs

[Muhammad Kamran <muhammad.kamran@arm.com>]

This series fixes a GDB inferior-call issue exposed by malloc being a GNU
IFUNC in glibc on AArch64.  The underlying problem is not AArch64-specific:
it can affect any inferior helper found through find_function_in_inferior's
minimal-symbol fallback when that helper is a GNU IFUNC.

GDB calls find_function_in_inferior ("malloc") when expression evaluation
needs to allocate memory in the inferior, for example for string literal
arguments.  In the minimal-symbol fallback, GDB created a synthetic ordinary
function pointer from the minimal symbol address.  If the symbol was a GNU
IFUNC, this lost the IFUNC marker, so call_function_by_hand did not resolve
the symbol before calling it.

Patch 1 checks the minimal symbol kind directly and propagates the GNU IFUNC
marker to the synthetic function type for mst_text_gnu_ifunc and
mst_data_gnu_ifunc symbols.  The existing fallback address and return type
are unchanged.

Patch 2 fixes the follow-on return-type issue after IFUNC resolution.  When
the resolved target type, or the type inferred from the resolver return type,
does not provide a usable return type, find_function_addr now keeps the
original function type's return type.  This preserves the synthetic fallback
return type used by find_function_in_inferior ("malloc").

The tests add an internal inferior-call case using an IFUNC malloc and run it
through the existing gdb.base/gnu-ifunc.exp matrix for resolver attr,
resolver debug info, and resolved-target debug info.

Changes since v2:
	* Rework the minimal-symbol fallback to check the minimal symbol kind
	  directly as suggested by Simon.
	* Add coverage for both debug and no-debug IFUNC malloc variants by
	  using the existing framework.
	* Preserve the original IFUNC return type when the resolved target type
	  is unknown.

Muhammad Kamran (2):
  gdb: Preserve IFUNC marker when finding inferior functions
  gdb: Keep original IFUNC return type when target type is unknown

 gdb/infcall.c                                 | 12 +++-
 .../gdb.base/gnu-ifunc-inferior-call-final.c  | 27 ++++++++
 .../gnu-ifunc-inferior-call-resolver.c        | 43 +++++++++++++
 .../gdb.base/gnu-ifunc-inferior-call.c        | 37 +++++++++++
 gdb/testsuite/gdb.base/gnu-ifunc.exp          | 61 +++++++++++++++++++
 gdb/valops.c                                  |  5 ++
 6 files changed, 183 insertions(+), 2 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-final.c
 create mode 100644 gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-resolver.c
 create mode 100644 gdb/testsuite/gdb.base/gnu-ifunc-inferior-call.c

-- 
2.43.0