From 6ea328f0f1865a75fdfd16cd8cca04818facdd26 Mon Sep 17 00:00:00 2001
From: Aidan MacDonald <amachronic@protonmail.com>
Date: Tue, 18 Feb 2025 16:47:41 +0000
Subject: [PATCH] arm: add div0 handler for 64-bit division on ARMv7-M

Even though ARMv7-M has a hardware divider, 64-bit division is
handled in software and needs a div0 handler. The libgcc routines
call __aeabi_{i,l}div0 so we alias those to __div0.

Change-Id: I5152c43d39e25e03f31404753f13978a614aca06
---
 apps/plugins/lib/gcc-support.c         | 5 +++++
 firmware/export/config.h               | 2 +-
 firmware/target/arm/system-arm-micro.c | 8 ++++++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/apps/plugins/lib/gcc-support.c b/apps/plugins/lib/gcc-support.c
index a2b709ba50..f1fbe4ec58 100644
--- a/apps/plugins/lib/gcc-support.c
+++ b/apps/plugins/lib/gcc-support.c
@@ -27,6 +27,11 @@ void __attribute__((naked)) __div0(void)
 {
     asm volatile("bx %0" : : "r"(rb->__div0));
 }
+
+#if defined(CPU_ARM_MICRO)
+void __aeabi_idiv0(void) __attribute__((alias("__div0")));
+void __aeabi_ldiv0(void) __attribute__((alias("__div0")));
+#endif
 #endif
 
 void *memcpy(void *dest, const void *src, size_t n)
diff --git a/firmware/export/config.h b/firmware/export/config.h
index 8ac710267b..ad5f45c98e 100644
--- a/firmware/export/config.h
+++ b/firmware/export/config.h
@@ -710,7 +710,7 @@ Lyre prototype 1 */
 # elif ARM_PROFILE == ARM_PROFILE_CLASSIC
 #  define CPU_ARM_CLASSIC
 # endif
-# if !defined(ARM_HAVE_HW_DIV) && (CONFIG_PLATFORM & PLATFORM_NATIVE)
+# if (CONFIG_PLATFORM & PLATFORM_NATIVE)
 #  define ARM_NEED_DIV0
 # endif
 #endif
diff --git a/firmware/target/arm/system-arm-micro.c b/firmware/target/arm/system-arm-micro.c
index d9e1111206..9e23a9fb02 100644
--- a/firmware/target/arm/system-arm-micro.c
+++ b/firmware/target/arm/system-arm-micro.c
@@ -38,6 +38,14 @@ void UIE(void)
     while (1);
 }
 
+void __div0(void)
+{
+    while (1);
+}
+
+void __aeabi_idiv0(void) __attribute__((alias("__div0")));
+void __aeabi_ldiv0(void) __attribute__((alias("__div0")));
+
 #define ATTR_IRQ_HANDLER __attribute__((weak, alias("UIE")))
 
 void nmi_handler(void) ATTR_IRQ_HANDLER;