Test semihosting calls (#280)

* Add a basic semihosting test.

* Need to configure semihosting on each target.

* WIP

* Parse "cannot insert breakpoint" message.

Also use sys.exit instead of exit, per new pylint's suggestion.

2 files changed, 155 insertions, 0 deletions

diff --git a/debug/programs/semihosting.c b/debug/programs/semihosting.c
new file mode 100644
index 0000000..2ceea8c
--- /dev/null
+++ b/debug/programs/semihosting.c
@@ -0,0 +1,73 @@
+#include <stdint.h>
+
+#include "semihosting.h"
+
+size_t strlen(const char *buf)
+{
+    int len = 0;
+    while (buf[len])
+        len++;
+    return len;
+}
+
+#define O_RDONLY         0
+#define O_WRONLY         1
+#define O_RDWR           2
+#define O_RDWR           2
+#define O_TRUNC		0x0800
+
+int errno;
+
+/* These semihosting functions came from the Freedom Metal source. */
+static int open(const char *name, int flags, int mode) {
+    int semiflags = 0;
+
+    switch (flags & (O_RDONLY | O_WRONLY | O_RDWR)) {
+    case O_RDONLY:
+        semiflags = 0; /* 'r' */
+        break;
+    case O_WRONLY:
+        if (flags & O_TRUNC)
+            semiflags = 4; /* 'w' */
+        else
+            semiflags = 8; /* 'a' */
+        break;
+    default:
+        if (flags & O_TRUNC)
+            semiflags = 6; /* 'w+' */
+        else
+            semiflags = 10; /* 'a+' */
+        break;
+    }
+
+    volatile semihostparam_t arg = {.param1 = (uintptr_t)name,
+                                    .param2 = (uintptr_t)semiflags,
+                                    .param3 = (uintptr_t)strlen(name)};
+
+    int ret = (int)semihost_call_host(SEMIHOST_SYS_OPEN, (uintptr_t)&arg);
+    if (ret == -1)
+        errno = semihost_call_host(SEMIHOST_SYS_ERRNO, 0);
+    return ret;
+}
+
+static ssize_t write(int file, const void *ptr, size_t len)
+{
+    volatile semihostparam_t arg = {.param1 = (uintptr_t)file,
+                                    .param2 = (uintptr_t)ptr,
+                                    .param3 = (uintptr_t)len};
+    ssize_t ret =
+        (ssize_t)semihost_call_host(SEMIHOST_SYS_WRITE, (uintptr_t)&arg);
+
+    return (len - ret);
+}
+
+int main()
+{
+    char *filename = NULL;
+    const char *message = "Hello, world!\n";
+    int fd;
+
+begin:
+    fd = open(filename, O_WRONLY, 0644);
+    write(fd, message, strlen(message));
+}
\ No newline at end of file
diff --git a/debug/programs/semihosting.h b/debug/programs/semihosting.h
new file mode 100644
index 0000000..201e414
--- /dev/null
+++ b/debug/programs/semihosting.h
@@ -0,0 +1,82 @@
+#include <sys/types.h>
+
+#ifndef _SEMIHOSTING_H_
+#define _SEMIHOSTING_H_
+
+// ----------------------------------------------------------------------------
+
+// Semihosting operations.
+enum Semihost_Sys_Op {
+    // Regular operations
+    SEMIHOST_SYS_CLOCK = 0x10,
+    SEMIHOST_SYS_CLOSE = 0x02,
+    SEMIHOST_SYS_ELAPSED = 0x30,
+    SEMIHOST_SYS_ERRNO = 0x13,
+    SEMIHOST_SYS_EXIT = 0x18,
+    SEMIHOST_SYS_EXIT_EXTENDED = 0x20,
+    SEMIHOST_SYS_FLEN = 0x0C,
+    SEMIHOST_SYS_GET_CMDLINE = 0x15,
+    SEMIHOST_SYS_HEAPINFO = 0x16,
+    SEMIHOST_SYS_ISERROR = 0x08,
+    SEMIHOST_SYS_ISTTY = 0x09,
+    SEMIHOST_SYS_OPEN = 0x01,
+    SEMIHOST_SYS_READ = 0x06,
+    SEMIHOST_SYS_READC = 0x07,
+    SEMIHOST_SYS_REMOVE = 0x0E,
+    SEMIHOST_SYS_RENAME = 0x0F,
+    SEMIHOST_SYS_SEEK = 0x0A,
+    SEMIHOST_SYS_SYSTEM = 0x12,
+    SEMIHOST_SYS_TICKFREQ = 0x31,
+    SEMIHOST_SYS_TIME = 0x11,
+    SEMIHOST_SYS_TMPNAM = 0x0D,
+    SEMIHOST_SYS_WRITE = 0x05,
+    SEMIHOST_SYS_WRITEC = 0x03,
+    SEMIHOST_SYS_WRITE0 = 0x04,
+};
+
+enum ADP_Code {
+    ADP_Stopped_BranchThroughZero = 0x20000,
+    ADP_Stopped_UndefinedInstr = 0x20001,
+    ADP_Stopped_SoftwareInterrupt = 0x20002,
+    ADP_Stopped_PrefetchAbort = 0x20003,
+    ADP_Stopped_DataAbort = 0x20004,
+    ADP_Stopped_AddressException = 0x20005,
+    ADP_Stopped_IRQ = 0x20006,
+    ADP_Stopped_FIQ = 0x20007,
+    ADP_Stopped_BreakPoint = 0x20020,
+    ADP_Stopped_WatchPoint = 0x20021,
+    ADP_Stopped_StepComplete = 0x20022,
+    ADP_Stopped_RunTimeErrorUnknown = 0x20023,
+    ADP_Stopped_InternalError = 0x20024,
+    ADP_Stopped_UserInterruption = 0x20025,
+    ADP_Stopped_ApplicationExit = 0x20026,
+    ADP_Stopped_StackOverflow = 0x20027,
+    ADP_Stopped_DivisionByZero = 0x20028,
+    ADP_Stopped_OSSpecific = 0x20029,
+};
+
+typedef struct {
+    uintptr_t param1;
+    uintptr_t param2;
+    uintptr_t param3;
+} semihostparam_t;
+
+static inline uintptr_t __attribute__((always_inline))
+semihost_call_host(uintptr_t op, uintptr_t arg) {
+    register uintptr_t r0 asm("a0") = op;
+    register uintptr_t r1 asm("a1") = arg;
+
+    asm volatile(".option push               \n"
+                 ".option norvc              \n"
+                 " slli    zero,zero,0x1f    \n"
+                 " ebreak                    \n"
+                 " srai    zero,zero,0x7     \n"
+                 ".option pop                \n"
+
+                 : "=r"(r0)         /* Outputs */
+                 : "r"(r0), "r"(r1) /* Inputs */
+                 : "memory");
+    return r0;
+}
+
+#endif
\ No newline at end of file