Compile error: Kernel module

Question

I am a newbie at kernel programming & I wish to run this kernel module (posted below)... and i ran the makefile (posted below) for that, but I am getting the following errors: Can someone please help me understand how to overcome this: The kernel program should run error free as it is taken from Intel's implementation:

obj-m += hello-1.o

all:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

This is the error:

snehil@ubuntu:~/Desktop/measure$ make
make -C /lib/modules/3.0.0-12-generic/build M=/home/snehil/Desktop/measure modules
make[1]: Entering directory `/usr/src/linux-headers-3.0.0-12-generic'
CC [M]  /home/snehil/Desktop/measure/measure1.o
/home/snehil/Desktop/measure/measure1.c: In function ‘hello_start’:
/home/snehil/Desktop/measure/measure1.c:108:2: error: implicit declaration of function
  ‘kmalloc’ [-Werror=implicit-function-declaration]
/home/snehil/Desktop/measure/measure1.c:108:8: warning: assignment makes pointer from  
 integer without a cast [enabled by default]
/home/snehil/Desktop/measure/measure1.c:115:11: warning: assignment makes pointer from
 integer without a cast [enabled by default]
/home/snehil/Desktop/measure/measure1.c:124:12: warning: assignment makes pointer from  
integer without a cast [enabled by default]
/home/snehil/Desktop/measure/measure1.c:130:13: warning: assignment makes pointer from
integer without a cast [enabled by default]
cc1: some warnings being treated as errors

make[2]: *** [/home/snehil/Desktop/measure/measure1.o] Error 1
make[1]: *** [_module_/home/snehil/Desktop/measure] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-3.0.0-12-generic'
make: *** [all] Error 2
snehil@ubuntu:~/Desktop/measure$ gcc measure1
gcc: error: measure1: No such file or directory
gcc: fatal error: no input files
compilation terminated.

This is the kernel module code:

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/hardirq.h>
#include <linux/preempt.h>
#include <linux/sched.h>

#define SIZE_OF_STAT 100000
#define BOUND_OF_LOOP 1000
#define UINT64_MAX (18446744073709551615ULL)

void inline Filltimes(uint64_t **times) {
unsigned long flags;
int i, j;
uint64_t start, end;
unsigned cycles_low, cycles_high, cycles_low1, cycles_high1;
volatile int variable = 0;

asm volatile ("CPUID\n\t"
"RDTSC\n\t"
"mov %%edx, %0\n\t"
"mov %%eax, %1\n\t": "=r" (cycles_high), "=r" (cycles_low)::"%rax", "%rbx", "%rcx", 
          "%rdx");
asm volatile ("CPUID\n\t"
"RDTSC\n\t"
"CPUID\n\t"
"RDTSC\n\t"
"mov %%edx, %0\n\t"
"mov %%eax, %1\n\t": "=r" (cycles_high), "=r" (cycles_low):: "%rax", "%rbx", "%rcx",
 "%rdx");
asm volatile ("CPUID\n\t"
"RDTSC\n\t"::: "%rax", "%rbx", "%rcx", "%rdx");


for (j=0; j<BOUND_OF_LOOP; j++) {
for (i =0; i<SIZE_OF_STAT; i++) { 

variable = 0;

preempt_disable();
raw_local_irq_save(flags);

asm volatile (
"CPUID\n\t"
"RDTSC\n\t"
"mov %%edx, %0\n\t"
"mov %%eax, %1\n\t": "=r" (cycles_high), "=r" (cycles_low):: "%rax", "%rbx", "%rcx", 
"%rdx");
/*call the function to measure here*/
asm volatile(
"CPUID\n\t"
"RDTSC\n\t"
"mov %%edx, %0\n\t"
 "mov %%eax, %1\n\t": "=r" (cycles_high1), "=r" (cycles_low1):: "%rax", "%rbx", "%rcx",
"%rdx");

raw_local_irq_restore(flags);
preempt_enable();


start = ( ((uint64_t)cycles_high << 32) | cycles_low );

end = ( ((uint64_t)cycles_high1 << 32) | cycles_low1 );

if ( (end - start) < 0) {
printk(KERN_ERR "\n\n>>>>>>>>>>>>>>  CRITICAL ERROR IN TAKING THE TIME!!!!!!\n loop(%d)
 stat(%d) start = %llu, end = %llu, variable = %u\n", j, i, start, end, variable);
times[j][i] = 0;
}
else 
{
times[j][i] = end - start;
}
}
}   
return;
}
uint64_t var_calc(uint64_t *inputs, int size)
{
 int i;
uint64_t acc = 0, previous = 0, temp_var = 0;
for (i=0; i< size; i++) {
if (acc < previous) goto overflow;
previous = acc;
acc += inputs[i];
}
acc = acc * acc;
if (acc < previous) goto overflow;
previous = 0;
for (i=0; i< size; i++){
if (temp_var < previous) goto overflow;
previous = temp_var;
temp_var+= (inputs[i]*inputs[i]);
}
 temp_var = temp_var * size;
if (temp_var < previous) goto overflow;
temp_var =(temp_var - acc)/(((uint64_t)(size))*((uint64_t)(size)));
 return (temp_var);
overflow:
printk(KERN_ERR "\n\n>>>>>>>>>>>>>> CRITICAL OVERFLOW ERROR IN var_calc!!!!!!\n\n");
return -EINVAL;
}
static int __init hello_start(void)
{
int i = 0, j = 0, spurious = 0, k =0;
uint64_t **times;
uint64_t *variances;
uint64_t *min_values;
uint64_t max_dev = 0, min_time = 0, max_time = 0, prev_min =0, tot_var=0,    
max_dev_all=0, var_of_vars=0, var_of_mins=0;

printk(KERN_INFO "Loading hello module...\n");

times = kmalloc(BOUND_OF_LOOP*sizeof(uint64_t*), GFP_KERNEL);
if (!times) {
printk(KERN_ERR "unable to allocate memory for times\n");
return 0;
}

for (j=0; j<BOUND_OF_LOOP; j++) {
times[j] = kmalloc(SIZE_OF_STAT*sizeof(uint64_t), GFP_KERNEL);
if (!times[j]) {
printk(KERN_ERR "unable to allocate memory for times[%d]\n", j);
for (k=0; k<j; k++)
kfree(times[k]);
return 0;
}
}

variances = kmalloc(BOUND_OF_LOOP*sizeof(uint64_t), GFP_KERNEL);
if (!variances) {
printk(KERN_ERR "unable to allocate memory for variances\n");
return 0;
}

min_values = kmalloc(BOUND_OF_LOOP*sizeof(uint64_t), GFP_KERNEL);
if (!min_values) {
printk(KERN_ERR "unable to allocate memory for min_values\n");
return 0;
}


Filltimes(times);

for (j=0; j<BOUND_OF_LOOP; j++) {

max_dev = 0;
min_time = 0;
max_time = 0;

for (i =0; i<SIZE_OF_STAT; i++) {
if ((min_time == 0)||(min_time > times[j][i]))
min_time = times[j][i];
if (max_time < times[j][i])
max_time = times[j][i];
}

max_dev = max_time - min_time;
min_values[j] = min_time;

if ((prev_min != 0) && (prev_min > min_time))
spurious++;
if (max_dev > max_dev_all)
max_dev_all = max_dev;

variances[j] = var_calc(times[j], SIZE_OF_STAT);
tot_var += variances[j];

printk(KERN_ERR "loop_size:%d >>>> variance(cycles): %llu; max_deviation: %llu ;min 
 time: %llu", j, variances[j], max_dev, min_time);

prev_min = min_time;
}

var_of_vars = var_calc(variances, BOUND_OF_LOOP);
var_of_mins = var_calc(min_values, BOUND_OF_LOOP);
printk(KERN_ERR "\n total number of spurious min values = %d", spurious);
printk(KERN_ERR "\n total variance = %llu", (tot_var/BOUND_OF_LOOP));
printk(KERN_ERR "\n absolute max deviation = %llu", max_dev_all);
printk(KERN_ERR "\n variance of variances = %llu", var_of_vars);
printk(KERN_ERR "\n variance of minimum values = %llu", var_of_mins);

for (j=0; j<BOUND_OF_LOOP; j++) {
kfree(times[j]);
}
kfree(times);
kfree(variances);
kfree(min_values);
return 0;
}

static void __exit hello_end(void)
{
printk(KERN_INFO "Goodbye Mr.\n");
}

module_init(hello_start);
module_exit(hello_end);

Answer 1

If you are using kmalloc or kzalloc() for memory allocation you have to include #include<linux/slab.h>. They are called as slab allocators, these slab are chunks i.e. "cache" present in RAM and are physically contiguous. These slab allocator use underlying "Buddy System Algorithm", buddy allocator to provide more fine-grained allocation.

Fore more referrence go through the below link: http://en.wikipedia.org/wiki/Slab_allocation http://en.wikipedia.org/wiki/Buddy_algorithm

Hope this answers your question!!!!!.

Answer 2

You haven't included the header for kmalloc. Add #include <linux/slab.h> to your code.