backup v8 before I blow everything up

Makefile

@@ -1,9 +1,11 @@
 .POSIX:
 
+ARCH = arm
 CC = $(PREFIX_PATH)-gcc
 # no-pie: https://stackoverflow.com/questions/51310756/how-to-gdb-step-debug-a-dynamically-linked-executable-in-qemu-user-mode
-CFLAGS = -fno-pie -ggdb3 -march=$(MARCH) -marm -pedantic -no-pie -std=c99 -Wall -Wextra #-mthumb
+CFLAGS = -fno-pie -ggdb3 -march=$(MARCH) -pedantic -no-pie -std=c99 -Wall -Wextra $(CFLAGS_EXTRA)
 CTNG =
+DEFAULT_SYSROOT = /usr/$(PREFIX)
 DRIVER_BASENAME = main
 DRIVER_OBJ = $(DRIVER_BASENAME)$(OBJ_EXT)
 IN_EXT = .S
@@ -13,14 +15,14 @@ OBJDUMP_EXT = .objdump
 OBJ_EXT = .o
 OUT_EXT = .out
 PREFIX = arm-linux-gnueabihf
-QEMU_EXE = qemu-arm
+QEMU_EXE = qemu-$(ARCH)
 RUN_CMD = $(QEMU_EXE) -L $(SYSROOT)
 GDB_PORT = 1234
 TEST = test
 
 ifeq ($(CTNG),)
   PREFIX_PATH = $(PREFIX)
-  SYSROOT = /usr/arm-linux-gnueabihf
+  SYSROOT = $(DEFAULT_SYSROOT)
 else
   PREFIX_PATH = $(CTNG)/$(PREFIX)/bin/$(PREFIX)
   SYSROOT = $(CTNG)/$(PREFIX)/$(PREFIX)/sysroot
@@ -35,13 +37,10 @@ OBJDUMPS := $(addsuffix $(OBJDUMP_EXT), $(INS_NOEXT))
 .PHONY: all clean objdump test
 .PRECIOUS: %$(OBJ_EXT)
 
-all: $(OUTS) hello_c$(OUT_EXT)
+all: $(OUTS)
 
 objdump: $(OBJDUMPS)
 
-hello_c$(OUT_EXT): hello_c.c
-	$(CC) $(CFLAGS) -o '$@' '$<'
-
 %$(OUT_EXT): %$(OBJ_EXT) $(DRIVER_OBJ)
 	$(CC) $(CFLAGS) -o '$@' '$<' $(DRIVER_OBJ)
 
@@ -62,11 +61,11 @@ gdb-%: %$(OUT_EXT)
 	gdb-multiarch -q \
 	  -nh \
 	  -ex 'set confirm off'  \
-	  -ex 'set architecture arm' \
+	  -ex 'set architecture $(ARCH)' \
 	  -ex 'set sysroot $(SYSROOT)' \
 	  -ex 'file $<' \
 	  -ex 'target remote localhost:$(GDB_PORT)' \
-	  -ex 'break asm_main' \
+	  -ex 'break asm_main_end' \
 	  -ex 'continue' \
 	  -ex 'layout split' \
 	;

README.adoc

@@ -93,6 +93,10 @@ Shortcut:
 ./t -g add
 ....
 
+This leaves us right at the end of `asm_main`, and at the start of the assembly code in the `.S` file.
+
+TODO: possible to restart the running program from GDB as in `gdbserver --multi`? Convenient as you can reuse breakpoints easily.
+
 Bibliography: https://stackoverflow.com/questions/20590155/how-to-single-step-arm-assembler-in-gdb-on-qemu/51310791#51310791
 
 === Disassemble
@@ -164,8 +168,8 @@ Non OS portable examples will be clearly labeled with their OS.
 These examples show how our tooling works:
 
 . link:fail.S[]
-. link:hello_c.c[]
 . link:hello_driver.S[]
+. link:hello_common.S[]
 
 === C driver
 
@@ -335,6 +339,8 @@ Unlike most our other examples, which use the C standard library for portability
 
 == ARMv8
 
+TODO I'm setting this up now, but it is segfaulting. Almost there I think.
+
 In this repository we will document only points where ARMv8 differs from ARMv7 behaviour: so you should likely learn ARMv7 first.
 
 ARMv8 is the 64 bit version of the ARM architecture.

add.S

@@ -4,6 +4,13 @@ ENTRY
 
     /* 1 + 2 = 3, immediates. */
     mov r0, #1
+    /* r1 = r0 + 2 */
+    add r1, r0, #2
+    cmp r1, #3
+    FAIL_IF(bne)
+
+    /* If src == dest, we can ommit one of them. */
+    mov r0, #1
     add r0, #2
     cmp r0, #3
     FAIL_IF(bne)

common.h

@@ -1,51 +1,8 @@
 #ifndef COMMON_H
 #define COMMON_H
 
-.extern exit, printf, puts
-
-/* Store all callee saved registers, and LR in case we make further BL calls.
- *
- * Also save the input arguments r0-r3 on the stack, so we can access them later on,
- * despite those registers being overwritten.
- */
-#define ENTRY \
-.text; \
-.global asm_main; \
-asm_main: \
-    stmdb sp!, { r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, lr }; \
-;
+#include "common_arch.h"
 
-/* Branching to "fail" makes tests fail with exit status 1.
- *
- * If EXIT is reached, the program ends successfully.
- *
- * Meant to be called at the end of ENTRY.
- *
- * Restore LR and jump to it to return from asm_main.
- *
- * * r0: line of failure
- */
-#define EXIT \
-    mov r0, #0; \
-    mov r1, #0; \
-    b pass; \
-fail: \
-    ldr r1, [sp]; \
-    str r0, [r1]; \
-    mov r0, #1; \
-pass: \
-    add sp, #16; \
-    ldmia sp!, { r4, r5, r6, r7, r8, r9, r10, r11, lr }; \
-    bx lr; \
-;
-
-#define FAIL_IF(condition) \
-    condition 1f; \
-    b 2f; \
-1: \
-    ldr r0, =__LINE__; \
-    b fail; \
-2: \
-;
+.extern exit, printf, puts
 
 #endif

common_arch.h

@@ -0,0 +1,48 @@
+#ifndef COMMON_ARCH_H
+#define COMMON_ARCH_H
+
+/* Store all callee saved registers, and LR in case we make further BL calls.
+ *
+ * Also save the input arguments r0-r3 on the stack, so we can access them later on,
+ * despite those registers being overwritten.
+ */
+#define ENTRY \
+.text; \
+.global asm_main; \
+asm_main: \
+    stmdb sp!, { r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, lr }; \
+asm_main_end: \
+;
+
+/* Meant to be called at the end of ENTRY.*
+ *
+ * Branching to "fail" makes tests fail with exit status 1.
+ *
+ * If EXIT is reached, the program ends successfully.
+ *
+ * Restore LR and bx jump to it to return from asm_main.
+ */
+#define EXIT \
+    mov r0, #0; \
+    mov r1, #0; \
+    b pass; \
+fail: \
+    ldr r1, [sp]; \
+    str r0, [r1]; \
+    mov r0, #1; \
+pass: \
+    add sp, #16; \
+    ldmia sp!, { r4, r5, r6, r7, r8, r9, r10, r11, lr }; \
+    bx lr; \
+;
+
+#define FAIL_IF(condition) \
+    condition 1f; \
+    b 2f; \
+1: \
+    ldr r0, =__LINE__; \
+    b fail; \
+2: \
+;
+
+#endif

hello_common.S

@@ -0,0 +1,6 @@
+/* Minimal example using common.h. */
+
+#include "common.h"
+
+ENTRY
+EXIT

hello_driver.S

@@ -3,8 +3,6 @@
  * Controls the exit status of the program.
  */
 
-#include "common.h"
-
 .text
 .global asm_main
 asm_main:

main.c

@@ -1,7 +1,7 @@
 #include "stdio.h"
 #include "stdint.h"
 
-int asm_main(uint32_t *line) __attribute__((target("arm")));
+int asm_main(uint32_t *line);
 
 int main(void) {
     uint32_t ret, line;

params.mk

@@ -0,0 +1,2 @@
+# The opposite of -mthumb.
+CFLAGS_EXTRA = -marm

v8/common.h

@@ -0,0 +1 @@
+../common.h

v8/common_arch.h

@@ -0,0 +1,41 @@
+#ifndef COMMON_ARCH_H
+#define COMMON_ARCH_H
+
+#define ENTRY \
+.text; \
+.global asm_main; \
+asm_main: \
+    sub  sp, sp, #0xA0; \
+    stp  x29, x30, [sp, #0x0]; \
+    stp  x27, x28, [sp, #0x10]; \
+    stp  x25, x26, [sp, #0x20]; \
+    stp  x23, x24, [sp, #0x30]; \
+    stp  x21, x22, [sp, #0x40]; \
+    stp  x19, x20, [sp, #0x50]; \
+    stp  x6, x7, [sp, #0x60]; \
+    stp  x4, x5, [sp, #0x80]; \
+    stp  x2, x3, [sp, #0x90]; \
+    stp  x0, x1, [sp, #0xA0]; \
+asm_main_end: \
+;
+
+#define EXIT \
+    mov w0, #0; \
+    mov w1, #0; \
+    b pass; \
+fail: \
+    ldr w1, [sp]; \
+    str w0, [x1]; \
+    mov w0, #1; \
+pass: \
+    ldp x19, x20, [sp, #0x50]; \
+    ldp x21, x22, [sp, #0x40]; \
+    ldp x23, x24, [sp, #0x30]; \
+    ldp x25, x26, [sp, #0x20]; \
+    ldp x27, x28, [sp, #0x10]; \
+    ldp x29, x30, [sp]; \
+    add sp, sp, #0xA0; \
+    ret; \
+;
+
+#endif

v8/hello_common.S

@@ -0,0 +1 @@
+../hello_common.S

v8/hello_driver.S

@@ -0,0 +1,5 @@
+.text
+.global asm_main
+asm_main:
+    mov w0, #0
+    ret

v8/mov.S

@@ -7,19 +7,19 @@
 
 ENTRY
 
-    /* Immediate. */
-    mov r0, #0
-    cmp r0, #0
-    FAIL_IF(bne)
-    mov r0, #1
-    cmp r0, #1
-    FAIL_IF(bne)
+    #/* Immediate. */
+    #mov r0, #0
+    #cmp r0, #0
+    #FAIL_IF(bne)
+    #mov r0, #1
+    #cmp r0, #1
+    #FAIL_IF(bne)
 
-    /* Register. */
-    mov r0, #0
-    mov r1, #1
-    mov r1, r0
-    cmp r1, #0
-    FAIL_IF(bne)
+    #/* Register. */
+    #mov r0, #0
+    #mov r1, #1
+    #mov r1, r0
+    #cmp r1, #0
+    #FAIL_IF(bne)
 
-    EXIT
+EXIT

v8/params.mk

@@ -1,2 +1,4 @@
+ARCH = aarch64
+DEFAULT_SYSROOT = /usr/aarch64-linux-gnu
 MARCH = armv8-a
 PREFIX = aarch64-linux-gnu