[kernel,cmds] Add sysctl system call and option get/set command

elks/arch/i86/kernel/strace.h

@@ -154,7 +154,7 @@ struct sc_info elks_table1[] = {
     ENTRY("sbrk",           packinfo(1, P_SSHORT, P_NONE,    P_NONE   )),
     ENTRY("ustatfs",        packinfo(3, P_USHORT, P_PDATA,   P_SSHORT )),   // 70
     ENTRY("setitimer",      packinfo(3, P_SSHORT, P_PDATA,   P_PDATA  )),
-    ENTRY(0,                packinfo(0, P_NONE,   P_NONE,    P_NONE   )),
+    ENTRY("sysctl",         packinfo(3, P_SSHORT, P_STR,     P_SSHORT )),
     ENTRY(0,                packinfo(0, P_NONE,   P_NONE,    P_NONE   )),
     ENTRY("uname",          packinfo(1, P_PDATA,  P_NONE,    P_NONE   )),   // 74
 };

elks/arch/i86/kernel/syscall.dat

@@ -92,6 +92,7 @@ setsid		+68	0
 sbrk		+69	2	* Legacy number from Linux
 ustatfs		+70	3
 setitimer	+71	3
+sysctl		+72	3	. ELKS
 uname		+74	1	. was knlvsn
 #
 # From /usr/include/asm-generic/unistd.h

elks/include/linuxmt/kernel.h

@@ -24,6 +24,7 @@
 
 extern char running_qemu;
 extern dev_t dev_console;
+extern int dprintk_on;
 
 extern void do_exit(int) noreturn;
 

elks/include/linuxmt/sysctl.h

@@ -0,0 +1,12 @@
+#ifndef __LINUXMT_SYSCTL_H
+#define __LINUXMT_SYSCTL_H
+
+/* sysctl(2) parameters */
+
+#define CTL_MAXNAMESZ   32      /* max size of option name */
+
+#define CTL_LIST        0       /* get option list from index */
+#define CTL_GET         (-1)    /* get option value by name */
+#define CTL_SET         (-2)    /* set option value by name */
+
+#endif

elks/init/main.c

@@ -73,7 +73,6 @@ static char *envp_init[MAX_INIT_ENVS+1];
 static unsigned char options[OPTSEGSZ];
 
 extern int boot_rootdev;
-extern int dprintk_on;
 static char * INITPROC root_dev_name(int dev);
 static int INITPROC parse_options(void);
 static void INITPROC finalize_options(void);

elks/kernel/Makefile

@@ -37,7 +37,7 @@ include $(BASEDIR)/Makefile-rules
 
 # unused: wait.o lock.o
 OBJS  = sched.o printk.o sleepwake.o version.o sys.o sys2.o fork.o \
-	exit.o time.o signal.o
+	exit.o time.o signal.o sysctl.o
 
 #########################################################################
 # Commands:

elks/kernel/sysctl.c

@@ -0,0 +1,63 @@
+#include <linuxmt/mm.h>
+#include <linuxmt/errno.h>
+#include <linuxmt/string.h>
+#include <linuxmt/sysctl.h>
+
+#include <linuxmt/trace.h>
+#include <linuxmt/kernel.h>
+
+struct sysctl {
+    const char *name;
+    int *value;
+};
+
+static int malloc_debug;
+static int net_debug;
+
+struct sysctl sysctl[] = {
+    { "kern.debug",         &dprintk_on         },  /* debug (^P) on/off */
+    { "kern.strace",        &tracing            },  /* strace=1, kstack=2 */
+    { "kern.console",       (int *)&dev_console },  /* console */
+    { "malloc.debug",       &malloc_debug       },
+    { "net.debug",          &net_debug          },
+};
+
+static char ctlname[CTL_MAXNAMESZ];
+
+#define ARRAYLEN(a)     (sizeof(a)/sizeof(a[0]))
+
+int sys_sysctl(int op, char *name, int *value)
+{
+    int error, n;
+    struct sysctl *sc;
+
+    if (op >= CTL_LIST) {
+        if (!name)
+            return -EFAULT;
+        if (op >= ARRAYLEN(sysctl))
+            return -ENOTDIR;
+        sc = &sysctl[op];
+        return verified_memcpy_tofs(name, (void *)sc->name, strlen(sc->name)+1);
+    }
+
+    n = strlen_fromfs(name, CTL_MAXNAMESZ) + 1;
+    if (n >= CTL_MAXNAMESZ) return -EFAULT;
+    error = verified_memcpy_fromfs(ctlname, name, n);
+    if (error) return error;
+    error = verfy_area(value, sizeof(int));
+    if (error) return error;
+
+    for (sc = sysctl;; sc++) {
+        if (sc >= &sysctl[ARRAYLEN(sysctl)]) return -ENOTDIR;
+        if (!strcmp(sc->name, ctlname))
+            break;
+    }
+
+    if (op == CTL_GET)
+            put_user(*sc->value, value);
+    else if (op == CTL_SET)
+            *sc->value = get_user(value);
+    else
+        return -EINVAL;
+    return 0;
+}

elkscmd/Applications

@@ -100,6 +100,7 @@ sys_utils/console               :sysutil                :1200k
 sys_utils/unreal16              :sysutil                            :1440c
 sys_utils/beep                  :sysutil                :1200k
 sys_utils/decomp                :sysutil         :360c          :1440k
+sys_utils/sysctl                :sysutil                :1200k
 screen/screen                   :screen                 :1200k
 cron/cron                       :cron                   :1200k
 cron/crontab                    :cron                   :1200k

elkscmd/sys_utils/.gitignore

@@ -22,6 +22,7 @@ ps
 reboot
 sercat
 shutdown
+sysctl
 umount
 unreal16
 who

elkscmd/sys_utils/Makefile

@@ -40,6 +40,7 @@ PRGS = \
 	console \
 	makeboot \
 	decomp \
+	sysctl \
 	# EOL
 
 HOSTPRGS = hostdecomp
@@ -125,6 +126,9 @@ unreal.o: $(ELKS_LIB)/unreal.S
 beep: beep.o
 	$(LD) $(LDFLAGS) -o beep beep.o $(LDLIBS)
 
+sysctl: sysctl.o
+	$(LD) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
 unreal16: unreal16.o unreal.o
 	$(LD) -melks-libc -mcmodel=small -c unreal16.S -o unreal16.o
 	$(LD) -melks-libc -mcmodel=small -nostdlib -o unreal16 unreal16.o unreal.o

elkscmd/sys_utils/sysctl.c

@@ -0,0 +1,105 @@
+/*
+ * sysctl - system control utility for ELKS
+ *
+ * 8 May 2024 Greg Haerr
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdarg.h>
+#include <sys/sysctl.h>
+
+#define errmsg(str) write(STDERR_FILENO, str, sizeof(str) - 1)
+
+static int digit(char c, int base)
+{
+    int d;
+    if (c <= '9') {
+        d = c - '0';
+    } else if (c < 'A') {   /* NEATLIBC bugfix */
+        return -1;
+    } else if (c <= 'Z') {
+        d = 10 + c - 'A';
+    } else {
+        d = 10 + c - 'a';
+    }
+    return d < base ? d : -1;
+}
+
+static int strtoi(const char *s)
+{
+    int num;
+    int dig;
+    int base;
+    int sgn = 1;
+
+    if (*s == '-')
+        sgn = ',' - *s++;
+    if (*s == '0') {
+        if (s[1] == 'x' || s[1] == 'X') {
+            base = 16;
+            s += 2;
+        } else
+            base = 8;
+    } else {
+        base = 10;
+    }
+    for (num = 0; (dig = digit(*s, base)) >= 0; s++)
+        num = num*base + dig;
+    num *= sgn;
+    return num;
+}
+
+static void msg(int fd, const char *s, ...)
+{
+    va_list va;
+
+    va_start(va, s);
+    do {
+        write(fd, s, strlen(s));
+        s = va_arg(va, const char *);
+    } while (s);
+    va_end(va);
+}
+
+int main(int ac, char **av)
+{
+    int i, ret, val;
+    char name[CTL_MAXNAMESZ];
+
+    if (ac < 2) {
+        errmsg("usage: sysctl [-a] [name[=value]]\n");
+        exit(-1);
+    }
+
+    if (av[1][0] == '-' && av[1][1] == 'a') {
+        for (i = 0;; i++) {
+            ret = sysctl(CTL_LIST+i, name, 0);
+            if (ret) exit(0);
+            ret = sysctl(CTL_GET, name, &val);
+            msg(STDOUT_FILENO, name, "=", itoa(val), "\n", 0);
+        }
+    }
+
+    for (i = 1; i < ac; i++) {
+        char *p = strchr(av[i], '=');
+        if (p) {
+            *p = '\0';
+            val = strtoi(p+1);
+            ret = sysctl(CTL_SET, av[i], &val);
+            if (ret) {
+                msg(STDOUT_FILENO, "Unknown option: ", av[i], "\n", 0);
+                continue;
+            }
+        }
+        ret = sysctl(CTL_GET, av[i], &val);
+        if (ret)
+            msg(STDERR_FILENO, "Invalid option: ", av[i], "\n", 0);
+        else {
+            msg(STDOUT_FILENO, av[i], "=", itoa(val), "\n", 0);
+        }
+    }
+    return ret;
+}

libc/include/sys/sysctl.h

@@ -0,0 +1,9 @@
+#ifndef __SYS_SYSCTL_H
+#define __SYS_SYSCTL_H
+
+#include <features.h>
+#include __SYSINC__(sysctl.h)
+
+int sysctl(int op, char *name, int *value);
+
+#endif