[PATCH v4 2/3] libgloss: arm: Add hardfault handler for M-profile

After reaching a hardfault, the simulator enters an infinite loop
unless we map the handler to 'abort'.

The patch adds this minimal setup for M-profile in the new
libgloss/arm/cpu-init/rdimon-aem-m.S and introduces the new
libgloss/arm/elf-mprofile-mps2.specs to add the mapping to the right
memory address.

2026-05-29  Andre Vieira <[email protected]>
	Christophe Lyon  <[email protected]>

	libgloss/
	* Makefile.in: Add entry for arm/mprofile-mps2.specs.
	* arm/Makefile.inc: Add entry for mprofile-mps2.specs.
	* arm/cpu-init/rdimon-aem-m.S: New file.
	* arm/cpu-init/rdimon-aem.S: Include rdimon-aem-m.S.
	* arm/elf-mprofile-mps2.specs: New file.
---
 libgloss/Makefile.in                 |  1 +
 libgloss/arm/Makefile.inc            |  3 ++-
 libgloss/arm/cpu-init/rdimon-aem-m.S | 39 ++++++++++++++++++++++++++++
 libgloss/arm/cpu-init/rdimon-aem.S   |  1 +
 libgloss/arm/elf-mprofile-mps2.specs | 26 +++++++++++++++++++
 5 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 libgloss/arm/cpu-init/rdimon-aem-m.S
 create mode 100644 libgloss/arm/elf-mprofile-mps2.specs

diff --git a/libgloss/Makefile.in b/libgloss/Makefile.in
index 5146a7880..c03ea4e6b 100644
--- a/libgloss/Makefile.in
+++ b/libgloss/Makefile.in
@@ -2255,6 +2255,7 @@ TEXINFO_TEX = ../texinfo/texinfo.tex
 @CONFIG_ARM_TRUE@	arm/aprofile-validation-v2m.specs \
 @CONFIG_ARM_TRUE@	arm/aprofile-ve-v2m.specs \
 @CONFIG_ARM_TRUE@	arm/aprofile-ve.specs arm/pid.specs \
+@CONFIG_ARM_TRUE@       arm/mprofile-mps2.specs \
 @CONFIG_ARM_TRUE@	arm/iq80310.specs
 @CONFIG_ARM_TRUE@arm_libgloss_linux_a_SOURCES = \
 @CONFIG_ARM_TRUE@	arm/linux-syscalls0.c \
diff --git a/libgloss/arm/Makefile.inc b/libgloss/arm/Makefile.inc
index 41fce3c99..5c740edcb 100644
--- a/libgloss/arm/Makefile.inc
+++ b/libgloss/arm/Makefile.inc
@@ -47,7 +47,8 @@ multilibtool_LIBRARIES += %D%/librdpmon.a
 	%D%/aprofile-validation.specs \
 	%D%/aprofile-validation-v2m.specs \
 	%D%/aprofile-ve-v2m.specs \
-	%D%/aprofile-ve.specs
+	%D%/aprofile-ve.specs \
+	%D%/mprofile-mps2.specs
 multilibtool_DATA += \
 	%D%/rdimon-crt0.o \
 	%D%/rdimon-crt0-v2m.o
diff --git a/libgloss/arm/cpu-init/rdimon-aem-m.S b/libgloss/arm/cpu-init/rdimon-aem-m.S
new file mode 100644
index 000000000..611849077
--- /dev/null
+++ b/libgloss/arm/cpu-init/rdimon-aem-m.S
@@ -0,0 +1,39 @@
+/* Copyright (c) 2026 ARM Ltd.  All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+ 1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+ 3. The name of the company may not be used to endorse or promote
+    products derived from this software without specific prior written
+    permission.
+
+ THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
+
+/* This file gives a basic initialisation of an M-profile core.
+
+   We define a hardfault handler, required to prevent the simulator
+   from entering into an infinite loop.  This handler is located at
+   address 0xc by default when linking with mprofile-mps2.specs which
+   uses --section-start=.hardfault_handler_addr=0xc.  */
+
+#if  (__ARM_ARCH_PROFILE == 'M')
+    /* On M-profile, call abort in case of hardfault: this causes the
+       simulator to abort execution instead of going into an infinite
+       loop.  */
+    .section .hardfault_handler_addr, "a"
+    .word abort
+#endif
diff --git a/libgloss/arm/cpu-init/rdimon-aem.S b/libgloss/arm/cpu-init/rdimon-aem.S
index 7bd086bbf..208257fe0 100644
--- a/libgloss/arm/cpu-init/rdimon-aem.S
+++ b/libgloss/arm/cpu-init/rdimon-aem.S
@@ -27,3 +27,4 @@
    manage multilibs without affecting the build system.  */
 
 #include "rdimon-aem-a.S"
+#include "rdimon-aem-m.S"
diff --git a/libgloss/arm/elf-mprofile-mps2.specs b/libgloss/arm/elf-mprofile-mps2.specs
new file mode 100644
index 000000000..edaf71917
--- /dev/null
+++ b/libgloss/arm/elf-mprofile-mps2.specs
@@ -0,0 +1,26 @@
+# rdimon.specs
+#
+# Spec file for AArch32 M profile baremetal newlib with version 2 of
+# the AngelAPI semi-hosting using the SVC trap instruction.
+#
+# This version supports extensibility through an extension mechanism.
+
+%rename link_gcc_c_sequence                rdimon_link_gcc_c_sequence
+
+%rename link old_link
+
+*link:
+--section-start=.hardfault_handler_addr=0xc %(old_link)
+
+*rdimon_libc:
+%{!specs=nano.specs:-lc} %{specs=nano.specs:-lc_nano}
+
+*rdimon_libgloss:
+%{!specs=nano.specs:-lrdimon} %{specs=nano.specs:-lrdimon_nano}
+
+*link_gcc_c_sequence:
+%(rdimon_link_gcc_c_sequence) --start-group %G %(rdimon_libc) %(rdimon_libgloss) --end-group
+
+*startfile:
+crti%O%s crtbegin%O%s cpu-init/rdimon-aem.o%s %{!pg:rdimon-crt0%O%s} %{pg:rdimon-crt0%O%s}
+
-- 
2.34.1