add directory study

2024-02-19 00:25:23 -05:00
parent b1306b38b1
commit f3774e2f8c
4001 changed files with 2285787 additions and 0 deletions
--- a/study/linux-travel/MINIX-1.5/1.5/Source/commands/chmem.c
+++ b/study/linux-travel/MINIX-1.5/1.5/Source/commands/chmem.c
@@ -0,0 +1,108 @@
+/* chmem - set total memory size for execution	Author: Andy Tanenbaum */
+
+#include <sys/types.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/* Should include a.out.h or exec.h.  Here is an approximation. */
+#define HLONG            8	/* header size in longs */
+#define TEXT             2	/* where is text size in header */
+#define DATA             3	/* where is data size in header */
+#define BSS              4	/* where is bss size in header */
+#define TOT              6	/* where in header is total allocation */
+#define TOTPOS          24	/* where is total in header */
+#define SEPBIT  0x00200000	/* this bit is set for separate I/D */
+#define MAGIC       0x0301	/* magic number for executable progs */
+#define MAX_8086   0x10000L	/* maximum allocation size for 8086 */
+#define MAX_386 0x7FFFFFFFL	/* etc */
+#define MAX_68K 0x7FFFFFFFL
+#define CPU_8086         4	/* CPU code for 8086 executables */
+#define CPU_386       0x10	/* etc */
+#define CPU_68K       0x0B	/* from Minix-PC a.out.h - unreliable */
+
+main(argc, argv)
+int argc;
+char *argv[];
+{
+/* The 8088 architecture does not make it possible to catch stacks that grow
+ * big.  The only way to deal with this problem is to let the stack grow down
+ * towards the data segment and the data segment grow up towards the stack.
+ * Normally, a total of 64K is allocated for the two of them, but if the
+ * programmer knows that a smaller amount is sufficient, he can change it
+ * using chmem.
+ *
+ * chmem =4096 prog  sets the total space for stack + data growth to 4096
+ * chmem +200  prog  increments the total space for stack + data growth by 200
+ */
+
+  char *p;
+  int fd, separate;
+  long lsize, olddynam, newdynam, newtot, overflow, header[HLONG];
+  char cpu;
+  long max;
+
+  if (argc != 3) usage();
+  p = argv[1];
+  if (*p != '=' && *p != '+' && *p != '-') usage();
+  lsize = atol(p + 1);
+
+  fd = open(argv[2], O_RDWR);
+  if (fd < 0) stderr3("chmem: can't open ", argv[2], "\n");
+
+  if (read(fd, (char *) header, sizeof(header)) != sizeof(header))
+	stderr3("chmem: ", argv[2], "bad header\n");
+  if ((header[0] & 0xFFFFL) != MAGIC)
+	stderr3("chmem: ", argv[2], " not executable\n");
+  separate = (header[0] & SEPBIT ? 1 : 0);
+
+  cpu = (char) (header[0] >> 24);	/* cpu byte is most significant */
+  if (cpu == CPU_8086 && *(unsigned short *) &header[0] != MAGIC)
+	cpu = CPU_68K;		/* 8086 code with 68K byte order == 68K */
+  switch(cpu) {
+	case CPU_8086:	max = MAX_8086;	break;
+	case CPU_386:	max = MAX_386;	break;
+	case CPU_68K:	max = MAX_68K;	break;
+	default:	stderr3("chmem: ", argv[2], "bad CPU type\n");
+  }  
+
+  if (lsize < 0) stderr3("chmem: ", p+1, " negative size not allowed\n");
+  if (lsize > max) stderr3("chmem: ", p + 1, " too large\n");
+
+  olddynam = header[TOT] - header[DATA] - header[BSS];
+  if (separate == 0) olddynam -= header[TEXT];
+
+  if (*p == '=')
+	newdynam = lsize;
+  else if (*p == '+')
+	newdynam = olddynam + lsize;
+  else if (*p == '-')
+	newdynam = olddynam - lsize;
+
+  newtot = header[DATA] + header[BSS] + newdynam;
+  if (separate == 0) newtot += header[TEXT];
+  overflow = (newtot > max ? newtot - max : 0);
+  newdynam -= overflow;
+  newtot -= overflow;
+  lseek(fd, (long) TOTPOS, SEEK_SET);
+  if (write(fd, (char *) &newtot, 4) < 0)
+	stderr3("chmem: can't modify ", argv[2], "\n");
+  printf("%s: Stack+malloc area changed from %ld to %ld bytes.\n",
+         argv[2], olddynam, newdynam);
+  exit(0);
+}
+
+usage()
+{
+  std_err("chmem {=+-} amount file\n");
+  exit(1);
+}
+
+stderr3(s1, s2, s3)
+char *s1, *s2, *s3;
+{
+  std_err(s1);
+  std_err(s2);
+  std_err(s3);
+  exit(1);
+}