asm: prefix every linux specific with linux/

userland/arch/arm/linux/build

@@ -0,0 +1 @@
+../build

userland/arch/arm/linux/c_from_asm.S

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+/* https://github.com/cirosantilli/arm-assembly-cheat#calling-convention */
+
+#include "common.h"
+
+.data
+puts_s:
+    .asciz "hello puts"
+printf_format:
+    .asciz "hello printf %x\n"
+my_array_0:
+    .word 0x11111111, 0x22222222, 0x33333333, 0x44444444
+my_array_1:
+    .word 0x55555555, 0x66666666, 0x77777777, 0x88888888
+
+ENTRY
+    /* puts("hello world") */
+    /* r0 is first argument. */
+    ldr r0, =puts_s
+    bl puts
+    /* Check exit status >= 0 for success. */
+    cmp r0, 0
+    ASSERT(bge)
+
+    /* printf */
+    ldr r0, =printf_format
+    ldr r1, =0x12345678
+    bl printf
+    cmp r0, 0
+    ASSERT(bge)
+
+    /* memcpy and memcmp. */
+
+        /* Smaller. */
+        ldr r0, =my_array_0
+        ldr r1, =my_array_1
+        ldr r2, =0x10
+        bl memcmp
+        cmp r0, 0
+        ASSERT(blt)
+
+        /* Copy. */
+        ldr r0, =my_array_0
+        ldr r1, =my_array_1
+        ldr r2, =0x10
+        bl memcpy
+
+        /* Equal. */
+        ldr r0, =my_array_0
+        ldr r1, =my_array_1
+        ldr r2, =0x10
+        bl memcmp
+        ASSERT_EQ(r0, 0)
+
+    /* exit(0) */
+    mov r0, 0
+    bl exit
+
+    /* Never reached, just for the fail symbol. */
+EXIT