Messages in this thread | | | From | Der Herr Hofrat <> | Subject | mmap question | Date | Tue, 24 Sep 2002 09:26:23 +0200 (CEST) |
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Hi !
trying to write up a simple mmap for a pseudo device that accesses a kmalloc'ed area.
The driver is a character driver that only has mmap implemented - the kmalloc is done in init module and the pointer to the buffer is in global context. I expected to be able to write to the mmap'ed area from user-space but it never shows up in kernel space (the printk in driver_mmap always shows the init_msg passed in init_module).
the basic framework I'm using is below - can anybody point me to an obvious error or to some docs that would explain how to share an kmalloc'ed area with user-space via mmap ?
thx ! hofrat
---driver--- char *kmalloc_area; ... static int driver_mmap(struct file *file, struct vm_area_struct *vma) { vma->vm_flags |= VM_LOCKED|VM_SHARED;
printk("message buffer: %s\",kmalloc_area); remap_page_range(vma->vm_start, virt_to_phys(kmalloc_area), LEN, PAGE_SHARED); return 0; } static struct file_operations simple_fops={ mmap: driver_mmap, };
int init_module(void){ ... kmalloc_area=kmalloc(LEN,GFP_USER); strncpy(kmalloc_area,init_msg,sizeof(init_msg)); ... }
---user-app---
int main(void) { int fd; char msg[]="some message - should appear in kernel space"; unsigned int *addr;
if((fd=open("/dev/simple-device", O_RDWR))<0) addr = mmap(0, LEN, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); memset(addr,0,LEN); strncpy(addr,msg,sizeof(msg)); return 0; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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