feat(build): add support for new binutils versions

Users of GNU ld (BPF) from binutils 2.39+ will observe multiple instaces
of a new warning when linking the bl*.elf in the form:

  ld.bfd: warning: stm32mp1_helper.o: missing .note.GNU-stack section implies executable stack
  ld.bfd: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
  ld.bfd: warning: bl2.elf has a LOAD segment with RWX permissions
  ld.bfd: warning: bl32.elf has a LOAD segment with RWX permissions

These new warnings are enbaled by default to secure elf binaries:
 - https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
 - https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=0d38576a34ec64a1b4500c9277a8e9d0f07e6774

Fix it in a similar way to what the Linux kernel does, see:
https://lore.kernel.org/all/20220810222442.2296651-1-ndesaulniers@google.com/

Following the reasoning there, we set "-z noexecstack" for all linkers
(although LLVM's LLD defaults to it) and optional add
--no-warn-rwx-segments since this a ld.bfd related.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Robert Schwebel <r.schwebel@pengutronix.de>
Change-Id: I9430f5fa5036ca88da46cd3b945754d62616b617

diff --git a/Makefile b/Makefile
index a69bfbb3b090db82c053137ae635ac3ce366a93c..04b75fe590b883045faa638455e2715752d2c31e 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -445,6 +445,8 @@ endif
 
 GCC_V_OUTPUT           :=      $(shell $(CC) -v 2>&1)
 
+TF_LDFLAGS             +=      -z noexecstack
+
 # LD = armlink
 ifneq ($(findstring armlink,$(notdir $(LD))),)
 TF_LDFLAGS             +=      --diag_error=warning --lto_level=O1
@@ -475,6 +477,9 @@ TF_LDFLAGS          +=      $(subst --,-Xlinker --,$(TF_LDFLAGS_$(ARCH)))
 
 # LD = gcc-ld (ld) or llvm-ld (ld.lld) or other
 else
+# With ld.bfd version 2.39 and newer new warnings are added. Skip those since we
+# are not loaded by a elf loader.
+TF_LDFLAGS             +=      $(call ld_option, --no-warn-rwx-segments)
 TF_LDFLAGS             +=      -O1
 TF_LDFLAGS             +=      --gc-sections