Minix1.5/commands/dis88/dismain.c
static char *sccsid =
"@(#) dismain.c, Ver. 2.1 created 00:00:00 87/09/01";
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* Copyright (C) 1987 G. M. Harding, all rights reserved *
* *
* Permission to copy and redistribute is hereby granted, *
* provided full source code, with all copyright notices, *
* accompanies any redistribution. *
* *
* This file contains the source code for the machine- *
* independent portions of a disassembler program to run *
* in a Unix (System III) environment. It expects, as its *
* input, a file in standard a.out format, optionally con- *
* taining symbol table information. If a symbol table is *
* present, it will be used in the disassembly; otherwise, *
* all address references will be literal (absolute). *
* *
* The disassembler program was originally written for an *
* Intel 8088 CPU. However, all details of the actual CPU *
* architecture are hidden in three machine-specific files *
* named distabs.c, dishand.c, and disfp.c (the latter *
* file is specific to the 8087 numeric co-processor). The *
* code in this file is generic, and should require mini- *
* mal revision if a different CPU is to be targeted. If a *
* different version of Unix is to be targeted, changes to *
* this file may be necessary, and if a completely differ- *
* ent OS is to be targeted, all bets are off. *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#include "dis.h" /* Disassembler declarations */
extern char *release; /* Contains release string */
static char *IFILE = NULL; /* Points to input file name */
static char *OFILE = NULL; /* Points to output file name */
static char *PRG; /* Name of invoking program */
static unsigned long zcount; /* Consecutive "0" byte count */
int objflg = 0; /* Flag: output object bytes */
#define unix 1
#define i8086 1
#define ibmpc 1
#if unix && i8086 && ibmpc /* Set the CPU identifier */
static int cpuid = 1;
#else
static int cpuid = 0;
#endif
/* * * * * * * MISCELLANEOUS UTILITY FUNCTIONS * * * * * * */
static void
usage(s)
register char *s;
{
fprintf(stderr,"Usage: %s [-o] ifile [ofile]\n",s);
exit(-1);
}
static void
fatal(s,t)
register char *s, *t;
{
fprintf(stderr,"\07%s: %s\n",s,t);
exit(-1);
}
static void
zdump(beg)
unsigned long beg;
{
beg = PC - beg;
if (beg > 1L)
printf("\t.zerow\t%ld\n",(beg >> 1));
if (beg & 1L)
printf("\t.byte\t0\n");
}
static char *
invoker(s)
register char *s;
{
register int k;
k = strlen(s);
while (k--)
if (s[k] == '/')
{
s += k;
++s;
break;
}
return (s);
}
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* This rather tricky routine supports the disdata() func- *
* tion. Its job is to output the code for a sequence of *
* data bytes whenever the object buffer is full, or when *
* a symbolic label is to be output. However, it must also *
* keep track of consecutive zero words so that lengthy *
* stretches of null data can be compressed by the use of *
* an appropriate assembler pseudo-op. It does this by *
* setting and testing a file-wide flag which counts suc- *
* cessive full buffers of null data. The function returns *
* a logical TRUE value if it outputs anything, logical *
* FALSE otherwise. (This enables disdata() to determine *
* whether to output a new synthetic label when there is *
* no symbol table.) *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
static int
objdump(c)
register char *c;
{/* * * * * * * * * * START OF objdump() * * * * * * * * * */
register int k;
int retval = 0;
if (objptr == OBJMAX)
{
for (k = 0; k < OBJMAX; ++k)
if (objbuf[k])
break;
if (k == OBJMAX)
{
zcount += k;
objptr = 0;
if (c == NULL)
return (retval);
}
}
if (zcount)
{
printf("\t.zerow\t%ld\n",(zcount >> 1));
++retval;
zcount = 0L;
}
if (objptr)
{
printf("\t.byte\t");
++retval;
}
else
return (retval);
for (k = 0; k < objptr; ++k)
{
printf("0x%02.2x",objbuf[k]);
if (k < (objptr - 1))
putchar(',');
else
putchar('\n');
}
objptr = 0;
return (retval);
}/* * * * * * * * * * END OF objdump() * * * * * * * * * */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* This routine, called at the beginning of the input *
* cycle for each object byte, and before any interpreta- *
* tion is attempted, searches the symbol table for any *
* symbolic name with a value corresponding to the cur- *
* rent PC and a type corresponding to the segment type *
* (i.e., text, data, or bss) specified by the function's *
* argument. If any such name is found, a pointer to it is *
* returned; otherwise, a NULL pointer is returned. *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
static char *
getlab(type)
register int type;
{/* * * * * * * * * * START OF getlab() * * * * * * * * * */
register int k;
static char b[32], c[10];
if (symptr < 0)
if ((type == N_TEXT)
|| ((type == N_DATA) && ( ! objptr ) && ( ! zcount )))
{
if (type == N_TEXT)
sprintf(b,"T%05.5lx:",PC);
else
sprintf(b,"D%05.5lx:",PC);
return (b);
}
else
return (NULL);
for (k = 0; k <= symptr; ++k)
if ((symtab[k].n_value == PC)
&& ((symtab[k].n_sclass & N_SECT) == type))
{
sprintf(b,"%s:\n",getnam(k));
if (objflg && (type != N_TEXT))
sprintf(c,"| %05.5lx\n",PC);
strcat(b,c);
return (b);
}
return (NULL);
}/* * * * * * * * * * * END OF getlab() * * * * * * * * * * */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* This routine performs a preliminary scan of the symbol *
* table, before disassembly begins, and outputs declara- *
* tions of globals and constants. *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
static void
prolog()
{/* * * * * * * * * * START OF prolog() * * * * * * * * * */
register int j, flag;
if (symptr < 0)
return;
for (j = flag = 0; j <= symptr; ++j)
if ((symtab[j].n_sclass & N_CLASS) == C_EXT)
if (((symtab[j].n_sclass & N_SECT) > N_UNDF)
&& ((symtab[j].n_sclass & N_SECT) < N_COMM))
{
char *c = getnam(j);
printf("\t.globl\t%s",c);
if (++flag == 1)
{
putchar('\t');
if (strlen(c) < 8)
putchar('\t');
printf("| Internal global\n");
}
else
putchar('\n');
}
else
if (symtab[j].n_value)
{
char *c = getnam(j);
printf("\t.comm\t%s,0x%08.8lx",c,
symtab[j].n_value);
if (++flag == 1)
printf("\t| Internal global\n");
else
putchar('\n');
}
if (flag)
putchar('\n');
for (j = flag = 0; j <= relptr; ++j)
if (relo[j].r_symndx < S_BSS)
{
char *c = getnam(relo[j].r_symndx);
++flag;
printf("\t.globl\t%s",c);
putchar('\t');
if (strlen(c) < 8)
putchar('\t');
printf("| Undef: %05.5lx\n",relo[j].r_vaddr);
}
if (flag)
putchar('\n');
for (j = flag = 0; j <= symptr; ++j)
if ((symtab[j].n_sclass & N_SECT) == N_ABS)
{
char *c = getnam(j);
printf("%s=0x%08.8lx",c,symtab[j].n_value);
if (++flag == 1)
{
printf("\t\t");
if (strlen(c) < 5)
putchar('\t');
printf("| Literal\n");
}
else
putchar('\n');
}
if (flag)
putchar('\n');
}/* * * * * * * * * * * END OF prolog() * * * * * * * * * * */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* This function is responsible for disassembly of the *
* object file's text segment. *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
static void
distext()
{/* * * * * * * * * * START OF distext() * * * * * * * * * */
char *c;
register int j;
register void (*f)();
for (j = 0; j < (int)(HDR.a_hdrlen); ++j)
getchar();
printf("| %s, %s\n\n",PRG,release);
printf("| @(");
printf("#)\tDisassembly of %s",IFILE);
if (symptr < 0)
printf(" (no symbols)\n\n");
else
printf("\n\n");
if (HDR.a_flags & A_EXEC)
printf("| File is executable\n\n");
if (HDR.a_flags & A_SEP)
{
printf("| File has split I/D space, and may have\n");
printf("| extraneous instructions in text segment\n\n");
}
prolog();
printf("\t.text\t\t\t| loc = %05.5lx, size = %05.5lx\n\n",
PC,HDR.a_text);
segflg = 0;
for (PC = 0L; PC < HDR.a_text; ++PC)
{
j = getchar() & 0xff;
if ((j == 0) && ((PC + 1L) == HDR.a_text))
{
++PC;
break;
}
if ((c = getlab(N_TEXT)) != NULL)
printf("%s",c);
f = optab[j].func;
(*f)(j);
}
}/* * * * * * * * * * END OF distext() * * * * * * * * * */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* This function handles the object file's data segment. *
* There is no good way to disassemble a data segment, be- *
* cause it is impossible to tell, from the object code *
* alone, what each data byte refers to. If it refers to *
* an external symbol, the reference can be resolved from *
* the relocation table, if there is one. However, if it *
* refers to a static symbol, it cannot be distinguished *
* from numeric, character, or other pointer data. In some *
* cases, one might make a semi-educated guess as to the *
* nature of the data, but such guesses are inherently *
* haphazard, and they are bound to be wrong a good por- *
* tion of the time. Consequently, the data segment is *
* disassembled as a byte stream, which will satisfy no *
* one but which, at least, will never mislead anyone. *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
static void
disdata()
{/* * * * * * * * * * START OF disdata() * * * * * * * * * */
register char *c;
register int j;
unsigned long end;
putchar('\n');
if (HDR.a_flags & A_SEP)
{
PC = 0L;
end = HDR.a_data;
}
else
end = HDR.a_text + HDR.a_data;
printf("\t.data\t\t\t| loc = %05.5lx, size = %05.5lx\n\n",
PC,HDR.a_data);
segflg = 0;
for (objptr = 0, zcount = 0L; PC < end; ++PC)
{
if ((c = getlab(N_DATA)) != NULL)
{
objdump(c);
printf("%s",c);
}
if (objptr >= OBJMAX)
if (objdump(NULL) && (symptr < 0))
printf("D%05.5lx:",PC);
j = getchar() & 0xff;
objbuf[objptr++] = j;
}
objdump("");
}/* * * * * * * * * * END OF disdata() * * * * * * * * * */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* This function handles the object file's bss segment. *
* Disassembly of the bss segment is easy, because every- *
* thing in it is zero by definition. *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
static void
disbss()
{/* * * * * * * * * * START OF disbss() * * * * * * * * * */
register int j;
register char *c;
unsigned long beg, end;
putchar('\n');
if (HDR.a_flags & A_SEP)
end = HDR.a_data + HDR.a_bss;
else
end = HDR.a_text + HDR.a_data + HDR.a_bss;
printf("\t.bss\t\t\t| loc = %05.5lx, size = %05.5lx\n\n",
PC,HDR.a_bss);
segflg = 0;
for (beg = PC; PC < end; ++PC)
if ((c = getlab(N_BSS)) != NULL)
{
if (PC > beg)
{
zdump(beg);
beg = PC;
}
printf("%s",c);
}
if (PC > beg)
zdump(beg);
}/* * * * * * * * * * * END OF disbss() * * * * * * * * * * */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* *
* This is the program entry point. The command line is *
* searched for an input file name, which must be present. *
* An optional output file name is also permitted; if none *
* is found, standard output is the default. One command- *
* line option is available: "-o", which causes the pro- *
* gram to include object code in comments along with its *
* mnemonic output. *
* *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
void
main(argc,argv)
int argc; /* Command-line args from OS */
register char **argv;
{/* * * * * * * * * * * START OF main() * * * * * * * * * * */
char a[1024];
register int fd;
long taboff, tabnum;
long reloff, relnum;
PRG = invoker(*argv);
while (*++argv != NULL) /* Process command-line args */
if (**argv == '-')
switch (*++*argv)
{
case 'o' :
if (*++*argv)
usage(PRG);
else
++objflg;
break;
default :
usage(PRG);
}
else
if (IFILE == NULL)
IFILE = *argv;
else if (OFILE == NULL)
OFILE = *argv;
else
usage(PRG);
if (IFILE == NULL)
usage(PRG);
else
if ((fd = open(IFILE,0)) < 0)
{
sprintf(a,"can't access input file %s",IFILE);
fatal(PRG,a);
}
if (OFILE != NULL)
if (freopen(OFILE,"w",stdout) == NULL)
{
sprintf(a,"can't open output file %s",OFILE);
fatal(PRG,a);
}
if ( ! cpuid )
fprintf(stderr,"\07%s: warning: host/cpu clash\n",PRG);
read(fd, (char *) &HDR,sizeof(struct exec));
if (BADMAG(HDR))
{
sprintf(a,"input file %s not in object format",IFILE);
fatal(PRG,a);
}
if (HDR.a_cpu != A_I8086)
{
sprintf(a,"%s is not an 8086/8088 object file",IFILE);
fatal(PRG,a);
}
if (HDR.a_hdrlen <= A_MINHDR)
HDR.a_trsize = HDR.a_drsize = 0L;
HDR.a_tbase = HDR.a_dbase = 0L;
/* AST emergency patch
HDR.a_lnums = HDR.a_toffs = 0L;
*/
reloff = HDR.a_text /* Compute reloc data offset */
+ HDR.a_data
+ (long)(HDR.a_hdrlen);
relnum =
(HDR.a_trsize + HDR.a_drsize) / sizeof(struct reloc);
taboff = reloff /* Compute name table offset */
+ HDR.a_trsize
+ HDR.a_drsize;
tabnum = HDR.a_syms / sizeof(struct nlist);
if (relnum > MAXSYM)
fatal(PRG,"reloc table overflow");
if (tabnum > MAXSYM)
fatal(PRG,"symbol table overflow");
if (relnum) /* Get reloc data */
if (lseek(fd,reloff,0) != reloff)
fatal(PRG,"lseek error");
else
{
for (relptr = 0; relptr < relnum; ++relptr)
read(fd, (char *) &relo[relptr],sizeof(struct reloc));
relptr--;
}
if (tabnum) /* Read in symtab */
if (lseek(fd,taboff,0) != taboff)
fatal(PRG,"lseek error");
else
{
for (symptr = 0; symptr < tabnum; ++symptr)
read(fd, (char *) &symtab[symptr],sizeof(struct nlist));
symptr--;
}
else
fprintf(stderr,"\07%s: warning: no symbols\n",PRG);
close(fd);
if (freopen(IFILE,"r",stdin) == NULL)
{
sprintf(a,"can't reopen input file %s",IFILE);
fatal(PRG,a);
}
distext();
disdata();
disbss();
exit(0);
}/* * * * * * * * * * * END OF main() * * * * * * * * * * */