1 files changed, 142 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/com32/gdbstub/main.c b/contrib/syslinux-4.02/com32/gdbstub/main.c
new file mode 100644
index 0000000..2ff9f28
--- /dev/null
+++ b/contrib/syslinux-4.02/com32/gdbstub/main.c
@@ -0,0 +1,142 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <console.h>
+#include <com32.h>
+#include <syslinux/loadfile.h>
+#include "serial.h"
+
+#define X86_INT_DB      1
+#define X86_INT_BP      3
+#define COM32_IDT       ((void*)0x100000)
+#define COM32_LOAD_ADDR ((void*)0x101000)
+#define STACK_SIZE      0x1000
+
+extern char _start[], _end[];
+
+struct reloc_info {
+    void *data;
+    size_t len;
+    uint32_t old_esp;
+    uint32_t reloc_base;
+};
+
+static inline void error(const char *msg)
+{
+    fputs(msg, stderr);
+}
+
+static inline uint32_t reloc_ptr(struct reloc_info *ri, void *ptr)
+{
+    return ri->reloc_base + (uint32_t) ((char *)ptr - _start);
+}
+
+static void hijack_interrupt(int intn, uint32_t handler)
+{
+    struct {
+	uint32_t lo;
+	uint32_t hi;
+    } *idt = COM32_IDT;
+
+    idt[intn].lo = (idt[intn].lo & 0xffff0000) | (handler & 0x0000ffff);
+    idt[intn].hi = (idt[intn].hi & 0x0000ffff) | (handler & 0xffff0000);
+}
+
+static void shift_cmdline(struct com32_sys_args *com32)
+{
+    char *p;
+
+    /* Skip leading whitespace */
+    for (p = com32->cs_cmdline; *p != '\0' && *p == ' '; p++) ;
+
+    /* Skip first word */
+    for (; *p != '\0' && *p != ' '; p++) ;
+
+    /* Skip whitespace after first word */
+    for (; *p != '\0' && *p == ' '; p++) ;
+
+    com32->cs_cmdline = p;
+}
+
+static __noreturn reloc_entry(struct reloc_info *ri)
+{
+    extern char int_handler[];
+    size_t stack_frame_size = sizeof(struct com32_sys_args) + 4;
+    struct com32_sys_args *com32;
+    uint32_t module_esp;
+
+    hijack_interrupt(X86_INT_DB, reloc_ptr(ri, int_handler));
+    hijack_interrupt(X86_INT_BP, reloc_ptr(ri, int_handler));
+
+    /* Copy module to load address */
+    memcpy(COM32_LOAD_ADDR, ri->data, ri->len);
+
+    /* Copy stack frame onto module stack */
+    module_esp = (ri->reloc_base - stack_frame_size) & ~15;
+    memcpy((void *)module_esp, (void *)ri->old_esp, stack_frame_size);
+
+    /* Fix up command line */
+    com32 = (struct com32_sys_args *)(module_esp + 4);
+    shift_cmdline(com32);
+
+    /* Set up CPU state to run module and enter GDB */
+    asm volatile ("movl %0, %%esp\n\t"
+		  "pushf\n\t"
+		  "pushl %%cs\n\t"
+		  "pushl %1\n\t"
+		  "jmp *%2\n\t"::"r" (module_esp),
+		  "c"(COM32_LOAD_ADDR), "r"(reloc_ptr(ri, int_handler))
+	);
+    for (;;) ;			/* shut the compiler up */
+}
+
+static inline __noreturn reloc(void *ptr, size_t len)
+{
+    extern uint32_t __entry_esp;
+    size_t total_size = _end - _start;
+    __noreturn(*entry_fn) (struct reloc_info *);
+    struct reloc_info ri;
+    uint32_t esp;
+    char *dest;
+
+    /* Calculate relocation address, preserve current stack */
+    asm volatile ("movl %%esp, %0\n\t":"=m" (esp));
+    dest = (char *)((esp - STACK_SIZE - total_size) & ~3);
+
+    /* Calculate entry point in relocated code */
+    entry_fn = (void *)(dest + ((char *)reloc_entry - _start));
+
+    /* Copy all sections to relocation address */
+    printf("Relocating %d bytes from %p to %p\n", total_size, _start, dest);
+    memcpy(dest, _start, total_size);
+
+    /* Call into relocated code */
+    ri.data = ptr;
+    ri.len = len;
+    ri.old_esp = __entry_esp;
+    ri.reloc_base = (uint32_t) dest;
+    entry_fn(&ri);
+}
+
+int main(int argc, char *argv[])
+{
+    void *data;
+    size_t data_len;
+
+    openconsole(&dev_null_r, &dev_stdcon_w);
+
+    if (argc < 2) {
+	error("Usage: gdbstub.c32 com32_file arguments...\n");
+	return 1;
+    }
+
+    if (loadfile(argv[1], &data, &data_len)) {
+	error("Unable to load file\n");
+	return 1;
+    }
+
+    serial_init();
+
+    /* No more lib calls after this point */
+    reloc(data, data_len);
+}