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authorStefan Hajnoczi <stefanha@gmail.com>2008-08-29 15:08:26 +0100
committerStefan Hajnoczi <stefanha@gmail.com>2008-08-29 15:08:26 +0100
commit77950e64a458e753900ff4ff6119bea15d1a4533 (patch)
tree3d00561537edc658061392b2e8400f21ececdd85 /com32/gdbstub/main.c
parent968a89b1417d24e3247c96950b434de1971b0d4e (diff)
downloadsyslinux.git-77950e64a458e753900ff4ff6119bea15d1a4533.tar.gz
syslinux.git-77950e64a458e753900ff4ff6119bea15d1a4533.tar.xz
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Add GDB stub
Diffstat (limited to 'com32/gdbstub/main.c')
-rw-r--r--com32/gdbstub/main.c76
1 files changed, 61 insertions, 15 deletions
diff --git a/com32/gdbstub/main.c b/com32/gdbstub/main.c
index 11c4e08b..8bb1dc5e 100644
--- a/com32/gdbstub/main.c
+++ b/com32/gdbstub/main.c
@@ -4,15 +4,44 @@
#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_RED_ZONE 0x1000
+#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;
@@ -32,52 +61,67 @@ static void shift_cmdline(struct com32_sys_args *com32)
com32->cs_cmdline = p;
}
-static __noreturn reloc_entry(void *ptr, size_t len, uintptr_t entry_esp, uintptr_t module_esp)
+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, ptr, len);
+ memcpy(COM32_LOAD_ADDR, ri->data, ri->len);
/* Copy stack frame onto module stack */
- module_esp = (module_esp - stack_frame_size) & ~15;
- memcpy((void*)module_esp, (void*)entry_esp, stack_frame_size);
+ 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*)((char*)module_esp + 4);
+ com32 = (struct com32_sys_args*)(module_esp + 4);
shift_cmdline(com32);
- /* Invoke module with stack set up */
+ /* Set up CPU state to run module and enter GDB */
asm volatile (
"movl %0, %%esp\n\t"
- "jmp *%%ecx"
- : : "r"(module_esp), "c"(COM32_LOAD_ADDR)
+ "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 uintptr_t __entry_esp;
- extern char _start[], _end[];
+ extern uint32_t __entry_esp;
size_t total_size = _end - _start;
- __noreturn (*success_fn)(void*, size_t, uintptr_t, uintptr_t);
+ __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_RED_ZONE - total_size) & ~3);
+ dest = (char*)((esp - STACK_SIZE - total_size) & ~3);
/* Calculate entry point in relocated code */
- success_fn = (void*)(dest + ((char*)reloc_entry - _start));
+ 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);
- success_fn(ptr, len, __entry_esp, (uintptr_t)dest);
+ /* 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[])
@@ -97,6 +141,8 @@ int main(int argc, char *argv[])
return 1;
}
+ serial_init();
+
/* No more lib calls after this point */
reloc(data, data_len);
}