o bug fixes
o dumps some TSS fields
o prints LDTs
Partial output on Linux 2.5.68-ce2 (note that you can now find the
doublefault handler and lcall entry points):
================================================================================
desc v0.60 -- dump i386 CPU descriptor tables
GDT at c0306280, 32 entries:
GDT#012: base=00000000 limit=ffffffff flags=c09b <P=1 DPL=0 32-bit Code>
GDT#013: base=00000000 limit=ffffffff flags=c093 <P=1 DPL=0 RW Data>
GDT#014: base=00000000 limit=ffffffff flags=c0fb <P=1 DPL=3 32-bit Code>
GDT#015: base=00000000 limit=ffffffff flags=c0f3 <P=1 DPL=3 RW Data>
GDT#016: base=c0353800 limit=000eb flags=008b <P=1 DPL=0 Busy TSS>
TSS at c0353800, 236 bytes:
CS:0000 <GDT#00,RPL0> EIP:00000000 EFLAGS:00000000
GDT#017: base=c0307c70 limit=00027 flags=0082 <P=1 DPL=0 LDT>
LDT at c0307c70, 5 entries:
LDT#000 [0x00]: flags=ec <P,DPL3,call> sel=60 <GDT#12,RPL0> off=c0108b60
LDT#004 [0x04]: flags=ec <P,DPL3,call> sel=60 <GDT#12,RPL0> off=c0108ba4
GDT#018: base=00000000 limit=00000fff flags=c09a <P=1 DPL=0 32-bit Code>
GDT#019: base=00000000 limit=00000fff flags=809a <P=1 DPL=0 16-bit Code>
GDT#020: base=00000000 limit=00000fff flags=8092 <P=1 DPL=0 RW Data>
GDT#021: base=00000000 limit=00000fff flags=8092 <P=1 DPL=0 RW Data>
GDT#022: base=00000000 limit=00000fff flags=8092 <P=1 DPL=0 RW Data>
GDT#023: base=00000000 limit=00000 flags=409a <P=1 DPL=0 32-bit Code>
GDT#024: base=00000000 limit=00000 flags=009a <P=1 DPL=0 16-bit Code>
GDT#025: base=00000000 limit=00000 flags=4092 <P=1 DPL=0 RW Data>
GDT#031: base=c0355600 limit=000eb flags=0089 <P=1 DPL=0 Available TSS>
TSS at c0355600, 236 bytes:
CS:0060 <GDT#12,RPL0> EIP:c010f700 EFLAGS:00000082
================================================================================
#define PROG_NAME "desc"
#define PROG_TITLE "dump i386 CPU descriptor tables"
#define VERSION "0.60"
#define AUTHOR "Chuck Ebbert <76306.1226ompuserve.com>"
#define LICENSE "Released under the GPL"
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
typedef struct { /* taken from Linux source */
unsigned short back_link,__blh;
unsigned long esp0;
unsigned short ss0,__ss0h;
unsigned long esp1;
unsigned short ss1,__ss1h;
unsigned long esp2;
unsigned short ss2,__ss2h;
unsigned long __cr3;
unsigned long eip;
unsigned long eflags;
unsigned long eax,ecx,edx,ebx;
unsigned long esp;
unsigned long ebp;
unsigned long esi;
unsigned long edi;
unsigned short es, __esh;
unsigned short cs, __csh;
unsigned short ss, __ssh;
unsigned short ds, __dsh;
unsigned short fs, __fsh;
unsigned short gs, __gsh;
unsigned short ldt, __ldth;
unsigned short trace, bitmap;
} __attribute__ ((packed)) tss_t;
typedef struct {
unsigned short limit;
unsigned int base;
} __attribute__ ((packed)) dtr_t;
typedef struct {
unsigned short off1;
unsigned short sel;
unsigned char none,flags;
unsigned short off2;
} __attribute__ ((packed)) idt_entry_t;
typedef struct {
unsigned a,b;
} __attribute__ ((packed)) gdt_ldt_entry_t;
/* read/write from kmem */
#define BUILD_IO_FN(fn_name, fn_fn) \
static int fn_name(int fd, int offset, void *buf, int size) { \
if (lseek(fd, offset, 0) != offset) return 0; \
if (fn_fn(fd, buf, size) != size) return 0; \
return size; \
}
BUILD_IO_FN(rkm, read)
BUILD_IO_FN(wkm, write)
int kmem;
void perr(char *err) { /* exit with err msg */
perror(err), exit(1);
}
/* read/write wrapper with err handling */
#define xkm(f, p1, p2, p3, p4, msg) { \
int _p4 = (p4); if ((f)((p1), (p2), (p3), _p4) != _p4) perr(msg); }
#define TEST_BIT(v,b) ( !!(v & (1 << b)) )
void dump_sys_desc(char *name, unsigned base, unsigned i) {
unsigned sel, flags;
idt_entry_t desc;
xkm(rkm, kmem, base + 8*i, &desc, sizeof(desc), "rkm sys");
sel = desc.sel, flags = desc.flags;
printf("%s#%03d [0x%02x]: flags=%02x <%s,DPL%d,%s>"
" sel=%02x <%s#%02d,RPL%d> off=%08x\n",
name, i, i, flags, flags & 0x80 ? "P" : "NP",
(flags & 0x60) >> 5,
(flags & 0x1f) == 0x0e ? "intr" :
(flags & 0x1f) == 0x0f ? "trap" :
(flags & 0x1f) == 0x05 ? "task" :
(flags & 0x1f) == 0x0c ? "call" : "????",
sel, sel & 4 ? "LDT" : "GDT", sel >> 3, sel & 3,
(unsigned)((desc.off2 << 16) | desc.off1));
}
void dump_gdt_ldt (char * name, unsigned base, unsigned num) {
unsigned dbase, dlimit, a, b, t, i, f;
gdt_ldt_entry_t desc;
tss_t tss;
printf("\n %s at %08x, %d entries:\n\n", name, base, num);
for (i = 0; i < num; i++) {
xkm(rkm, kmem, base + 8*i, &desc, sizeof(desc), "rkm gdtldt");
a = desc.a, b = desc.b, f = (b & 0xf0ff00) >> 8, t = f & 0x1f;
if (!a & !b)
continue;
if (t == 0x0c) { /* call gate */
dump_sys_desc(name, base, i);
continue;
}
dbase = (b & 0xff000000) | ((b & 0xff) << 16) | (a >> 16);
dlimit = (a & 0xffff) | (b & 0x0f0000);
printf("%s#%03d: base=%08x limit=%05x%s"
"\tflags=%04x <P=%d DPL=%d %s>\n",
name, i, dbase, dlimit, TEST_BIT(b,23) ? "fff" : "",
f, TEST_BIT(b,15), (b & 0x6000) >> 13,
t == 0x0b ? "Busy TSS" :
t == 0x09 ? "Available TSS" :
t == 0x02 ? "LDT" :
(f & 0x401c) == 0x4018 ? "32-bit Code" :
(f & 0x401c) == 0x18 ? "16-bit Code" :
(t & 0x1c) == 0x1c ? "Conforming code" :
(t & 0x1e) == 0x10 ? "RO Data" :
(t & 0x1e) == 0x12 ? "RW Data" :
(t & 0x1c) == 0x14 ? "Exp-down data" :
"Unknown");
if (t == 0x02)
dump_gdt_ldt(" LDT", dbase, dlimit + 1 >> 3);
if ((t == 0x09) | (t == 0x0b)) {
xkm(rkm, kmem, dbase, &tss, sizeof(tss), "rkm tss");
printf("\n TSS at %08x, %d bytes:\n\n",
dbase, dlimit + 1);
printf(" CS:%04x <%s#%02d,RPL%d>"
" EIP:%08x EFLAGS:%08x\n\n",
tss.cs, tss.cs & 4 ? "LDT" : "GDT",
tss.cs >> 3, tss.cs & 3,
tss.eip, tss.eflags);
}
}
printf("\n");
}
void dump_idt (unsigned base, unsigned num) {
int i;
printf(" IDT at %08x, %d entries:\n\n", base, num);
for (i = 0; i < num; i++) {
dump_sys_desc("IDT", base, i);
}
}
main() {
dtr_t gdtr, idtr;
printf(PROG_NAME " v" VERSION " -- " PROG_TITLE "\n");
kmem = open("/dev/kmem", O_RDONLY);
if (kmem < 0) perr("open kmem");
asm("sgdt %0" : "=m" (gdtr));
dump_gdt_ldt("GDT", gdtr.base, gdtr.limit + 1 >> 3);
asm("sidt %0" : "=m" (idtr));
dump_idt(idtr.base, idtr.limit + 1 >> 3);
close(kmem);
}
------
Chuck
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