From 16a7a47a31f07926475cb6b7fadbd07b5ce13a4d Mon Sep 17 00:00:00 2001
From: cnlohr <lohr85@gmail.com>
Date: Tue, 14 Mar 2023 07:21:17 -0400
Subject: [PATCH] * Add self-modifying code example. * Add ability to wait
for debugger to attach
---
ch32v003fun/ch32v003fun.c | 6 ++
ch32v003fun/ch32v003fun.h | 3 +
examples/self_modify_code/Makefile | 46 +++++++++++++
examples/self_modify_code/self_modify_code.c | 71 ++++++++++++++++++++
4 files changed, 126 insertions(+)
create mode 100644 examples/self_modify_code/Makefile
create mode 100644 examples/self_modify_code/self_modify_code.c
diff --git a/ch32v003fun/ch32v003fun.c b/ch32v003fun/ch32v003fun.c
index a97d1f8..72f14f2 100644
--- a/ch32v003fun/ch32v003fun.c
+++ b/ch32v003fun/ch32v003fun.c
@@ -896,6 +896,7 @@ int _write(int fd, const char *buf, int size)
while( ((*DMDATA0) & 0x80) )
if( timeout-- == 0 ) return place;
+ timeout = 160000;
uint32_t d;
int t = 3;
@@ -925,8 +926,13 @@ void SetupDebugPrintf()
{
// Clear out the sending flag.
*DMDATA1 = 0x0;
+ *DMDATA0 = 0x80;
}
+void WaitForDebuggerToAttach()
+{
+ while( ((*DMDATA0) & 0x80) );
+}
void DelaySysTick( uint32_t n )
{
diff --git a/ch32v003fun/ch32v003fun.h b/ch32v003fun/ch32v003fun.h
index 3115d7c..34ee9b1 100644
--- a/ch32v003fun/ch32v003fun.h
+++ b/ch32v003fun/ch32v003fun.h
@@ -4851,6 +4851,9 @@ void SetupUART( int uartBRR );
void SetupDebugPrintf();
+void WaitForDebuggerToAttach();
+
+
#ifdef __cplusplus
};
#endif
diff --git a/examples/self_modify_code/Makefile b/examples/self_modify_code/Makefile
new file mode 100644
index 0000000..ebe3d0b
--- /dev/null
+++ b/examples/self_modify_code/Makefile
@@ -0,0 +1,46 @@
+TARGET:=self_modify_code
+
+all : flash
+
+PREFIX:=riscv64-unknown-elf
+
+GPIO_Toggle:=EXAM/GPIO/GPIO_Toggle/User
+
+CH32V003FUN:=../../ch32v003fun
+MINICHLINK:=../../minichlink
+
+CFLAGS:= \
+ -g -Os -flto -ffunction-sections \
+ -static-libgcc -lgcc \
+ -march=rv32ec \
+ -mabi=ilp32e \
+ -I/usr/include/newlib \
+ -I$(CH32V003FUN) \
+ -nostdlib \
+ -I.
+
+LDFLAGS:=-T $(CH32V003FUN)/ch32v003fun.ld -Wl,--gc-sections
+
+SYSTEM_C:=$(CH32V003FUN)/ch32v003fun.c
+
+$(TARGET).elf : $(SYSTEM_C) $(TARGET).c
+ $(PREFIX)-gcc -o $@ $^ $(CFLAGS) $(LDFLAGS)
+
+$(TARGET).bin : $(TARGET).elf
+ $(PREFIX)-size $^
+ $(PREFIX)-objdump -S $^ > $(TARGET).lst
+ $(PREFIX)-objdump -t $^ > $(TARGET).map
+ $(PREFIX)-objcopy -O binary $< $(TARGET).bin
+ $(PREFIX)-objcopy -O ihex $< $(TARGET).hex
+
+flash : $(TARGET).bin
+ make -C $(MINICHLINK) all
+ $(MINICHLINK)/minichlink -w $< flash -b
+
+monitor : flash
+ $(MINICHLINK)/minichlink -T
+
+
+clean :
+ rm -rf $(TARGET).elf $(TARGET).bin $(TARGET).hex $(TARGET).lst $(TARGET).map $(TARGET).hex
+
diff --git a/examples/self_modify_code/self_modify_code.c b/examples/self_modify_code/self_modify_code.c
new file mode 100644
index 0000000..40f0940
--- /dev/null
+++ b/examples/self_modify_code/self_modify_code.c
@@ -0,0 +1,71 @@
+/* Small example showing how to use the SWIO programming pin to
+ do printf through the debug interface */
+
+#define SYSTEM_CORE_CLOCK 24000000
+#include "ch32v003fun.h"
+#include <stdio.h>
+
+uint32_t count;
+
+
+
+uint32_t ReadCSRSelfModify( uint16_t whichcsr ) __attribute__(( section(".data"))) __attribute__((noinline));
+uint32_t ReadCSRSelfModify( uint16_t whichcsr )
+{
+ uint32_t ret;
+
+ // Tricky: GCC will make this variable "point to" the opcode
+ // of the csrr instruction below.
+ volatile extern uint32_t readCSRLabel;
+
+ // We have to put this here to "force" the compiler to order the
+ // instructions in this way. Otherwise, the compiler will try
+ // to optimize the code and inline the assembly int something where
+ // our global handle into assembly code becomes meaningless.
+ asm volatile( "nop" );
+
+ // 000026f3 is csrrs a3, 0x000, x0; So, we modify it, placing the
+ // CSR we want to read in the top 12 bits of the instruction.
+
+ readCSRLabel = 0x000026f3 | (whichcsr << 20);
+
+ // The actual assembly block inserted into the C function. This
+ // defines the local label, globally, so the linker will be able to
+ // pick it up. We also need to used a fixed register, a3, so we
+ // can know what opcode we want to use, then we can let C tell us
+ // what register it would like the value in.
+ //
+ // The constraints are "ret" is a "write" register, and register a3
+ // is going to be clobbered by the assembly code.
+ asm volatile(
+ ".global readCSRLabel \n"
+ "readCSRLabel: \n"
+ " csrrs a3, 0x000, x0 \n"
+ " addi %[ret], a3, 0 \n"
+ : [ret]"=r"(ret) : : "a3" );
+
+ return ret;
+}
+
+
+int main()
+{
+ SystemInit48HSI();
+ SetupDebugPrintf();
+
+ WaitForDebuggerToAttach();
+
+ // Enable GPIOs
+ RCC->APB2PCENR |= RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOC;
+ puts( "Print all non-zero CSRs:" );
+ int i;
+ for( i = 0x000; i < 0x1000; i++ )
+ {
+ uint32_t rv = ReadCSRSelfModify( i );
+ if( rv )
+ printf( "%03x = %08x\n", i, rv );
+ }
+ printf( "Done\n" );
+ for(;;);
+}
+
--
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