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Hi,
I'm writing a kernel module (char device) to communicate some data
(execution trace) from the kernel space to the user space.
My traces are contains in a 512K buffer allocate with vmalloc.
When I try to send them to userspace using copy_to_user, it failed.
So I try to send them in 4K part to avoid this issue. But it failed too.
I copy my code at the end of the mail if anyone have an idea
piga_buffer_user_len is the size of my buffer.
piga_buffer_user is my buffer.
buf is the char * from userspace.
On the user size, I simply do a read with a buffer of 512K (more than
enough because piga_buffer_user_len is always less than that).
Thanks in advance
PS: the code crash on the copy_to_user that reach the 4K size i.e. if I
do one with 4000b it will past but if i do a second one after of 100b it
will crash.
while (piga_buffer_user_len) {
if (count < piga_buffer_user_len) {
printk(KERN_INFO "PIGA-Kernel: Size buffer %d below
requested %d\n",count,piga_buffer_user_len);
retval = -EFAULT;
} else {
int offset;
//offset = src & (PAGE_SIZE-1);
offset=0;
if (piga_buffer_user_len > (PAGE_SIZE-offset)) {
char * kzbuf;
kzbuf = kzalloc((PAGE_SIZE-offset), GFP_KERNEL);
memcpy(kzbuf,piga_buffer_user, (PAGE_SIZE-offset));
printk(KERN_INFO "PIGA-Kernel: (%p) Partial copy buffer
(%p:%p)
size(%ld)\n",buf,piga_buffer_user,(piga_buffer_user+PAGE_SIZE),(PAGE_SIZE-offset));
reter = copy_to_user(buf, kzbuf, (PAGE_SIZE-offset));
if (reter != 0) {
char *ctm = vmalloc(PAGE_SIZE);
memcpy(ctm,kzbuf,PAGE_SIZE-offset);
printk(KERN_INFO "PIGA-Kernel: error in copying to
userspace (%s)\n",ctm);
vfree(ctm);
retval = -EFAULT;
break;
}
kfree(kzbuf);
piga_buffer_user_len -= (PAGE_SIZE-offset);
piga_buffer_user += (PAGE_SIZE-offset);
//src += (PAGE_SIZE-offset);
buf += (PAGE_SIZE-offset);
} else {
char * kzbuf;
kzbuf = kzalloc((PAGE_SIZE-offset), GFP_KERNEL);
memcpy(kzbuf,piga_buffer_user, piga_buffer_user_len);
printk(KERN_INFO "PIGA-Kernel: (%p) Final copy
buffer\n",buf);
piga_buffer_user_len = 0;
reter = copy_to_user(buf, kzbuf, piga_buffer_user_len);
if (reter != 0) {
retval = -EFAULT;
break;
}
kfree(kzbuf);
buf += piga_buffer_user_len;
}
}
}
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