Work around qemu not (yet) setting the stack pointer

esp32c3/build.mk

@@ -12,7 +12,7 @@ CWD         ?= $(realpath $(CURDIR))
 FLASH_ADDR  ?= 0  # 2nd stage bootloader flash offset
 DOCKER      ?= docker run -it --rm -v $(CWD):$(CWD) -v $(MDK):$(MDK) -w $(CWD) mdashnet/riscv
 TOOLCHAIN   ?= $(DOCKER) riscv-none-elf
-SRCS        ?= $(MDK)/$(ARCH)/boot.c $(SOURCES)
+SRCS        ?= $(MDK)/$(ARCH)/boot.c $(MDK)/$(ARCH)/emulator_workarounds.S $(SOURCES)
 
 build: $(PROG).bin
 

esp32c3/emulator_workarounds.S

+//; In the current state of our emulator, it doesn't run a proper boot ROM.
+//; This function does some minor fixups (setting stack pointer etc.)
+//; and runs the MDK init function.
+.section .text
+.align 2
+.global emulator_workarounds
+emulator_workarounds:
+//; Not sure if this is the best address for the stack
+//; FIXME: This should be set to a range specified in the linker script
+li sp, 0x40384400
+//; Jump to MDK's real setup function
+j _reset

esp32c3/link.ld

@@ -5,7 +5,7 @@ MEMORY {
 }
 
 _eram = ORIGIN(dram) + LENGTH(dram);
-ENTRY(_reset)
+ENTRY(emulator_workarounds)
 
 SECTIONS {
   .text     : { *(.text) *(.text*) } > iram