FreeBSD Kmod Cannot find sys/param.h

Question

I am reading FreeBSD Device Drivers book. The first example is hello.c. But, When I am compiling it, it says hello.c:1:10: fatal error: 'sys/param.h' file not found

hello.c

#include <sys/param.h>
#include <sys/module.h>
#include <sys/kernel.h>
#include <sys/systm.h>

static int
hello_modevent(module_t mod __unused, int event, void *arg __unused)
{
    int error = 0;
    switch (event)
    {
        case MOD_LOAD:
            uprintf("Hello, world\n");
        case MOD_UNLOAD:
            uprintf("GoodBye, cruel world");
        default:
             error = EOPNETSUPP;
    }

return (error);
}

static moduledata_t hello_mod = {
   "hello",
   hello_modevent,
   NULL
}

DECLARE_MODULE(hello, hello_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE); 

Makefile

KMOD= hello
SRCS= hello.c

.include <bsd.kmod.mk>

uname -a FreeBSD FreeBSD-1 10.0-RELEASE FreeBSD 10.0-RELEASE #0 r260789: Fri Jan 17 01:46:25 UTC 2014 root@snap.freebsd.org:/usr/obj/usr/src/sys/GENERIC i386

Thank you very much. Add:

After I type make, the problem is
Warning: Object directory not changed from original /usr/home/user/Workplaces/hello
cc -O2 -pipe -fno-strict-aliasing -Werror -D_KERNEL -DKLD_MODULE -nostdinc   -I. -I@ -I@/contrib/altq -fno-common   -mno-aes -mno-avx -mno-mmx -mno-sse -msoft-float -ffreestanding -fstack-protector -std=iso9899:1999 -Qunused-arguments -fstack-protector -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual  -Wundef -Wno-pointer-sign -fformat-extensions  -Wmissing-include-dirs -fdiagnostics-show-option  -Wno-error-tautological-compare -Wno-error-empty-body  -Wno-error-parentheses-equality  -c hello.c
hello.c:1:10: fatal error: 'sys/param.h' file not found
#include <sys/param.h>
         ^
1 error generated.
*** Error code 1

Answer 1

I didn't change any thing except recompiling the kernel. The problem has been settled, though I do not know the reason. Thanks.

Answer 2

You need to have the kernel source installed if you want to build modules.

Additionally, your code has some errors:

> make
Warning: Object directory not changed from original /home/rsmith/tmp/src/foo
cc -O2 -pipe -fno-strict-aliasing -Werror -D_KERNEL -DKLD_MODULE -nostdinc   -I. -I@ -I@/contrib/altq -fno-common  -fno-omit-frame-pointer  -mno-aes -mno-avx -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float  -fno-asynchronous-unwind-tables -ffreestanding -fstack-protector -std=iso9899:1999 -Qunused-arguments -fstack-protector -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual  -Wundef -Wno-pointer-sign -fformat-extensions  -Wmissing-include-dirs -fdiagnostics-show-option  -Wno-error-tautological-compare -Wno-error-empty-body  -Wno-error-parentheses-equality -c hello.c
hello.c:17:22: error: use of undeclared identifier 'EOPNETSUPP'
             error = EOPNETSUPP;
                     ^
hello.c:27:2: error: expected ';' after top level declarator
}
 ^
 ;
2 errors generated.
*** [hello.o] Error code 1

The constant EOPNETSUPP should be EOPNOTSUPP from /usr/src/sys/sys/errno.h.

The code should look like this:

#include <sys/param.h>
#include <sys/module.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/errno.h>

static int
hello_modevent(module_t mod __unused, int event, void *arg __unused)
{
    int error = 0;
    switch (event)
    {
        case MOD_LOAD:
            uprintf("Hello, world\n");
        case MOD_UNLOAD:
            uprintf("GoodBye, cruel world");
        default:
             error = EOPNOTSUPP;
    }

return (error);
}

static moduledata_t hello_mod = {
   "hello",
   hello_modevent,
   NULL
};

DECLARE_MODULE(hello, hello_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);

This compiles fine on my machine, FreeBSD 9.2-RELEASE amd64