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vmcore: Convert __read_vmcore to use an iov_iter
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This gets rid of copy_to() and let us use proc_read_iter() instead
of proc_read().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
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@intel-lab-lkp
Matthew Wilcox (Oracle) authored and intel-lab-lkp committed Dec 13, 2021
1 parent e1684ad commit 687563a
Showing 1 changed file with 31 additions and 52 deletions.
83 changes: 31 additions & 52 deletions fs/proc/vmcore.c
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Expand Up @@ -251,22 +251,8 @@ ssize_t __weak copy_oldmem_page_encrypted(struct iov_iter *iter,
return copy_oldmem_page(iter, pfn, csize, offset);
}

/*
* Copy to either kernel or user space
*/
static int copy_to(void *target, void *src, size_t size, int userbuf)
{
if (userbuf) {
if (copy_to_user((char __user *) target, src, size))
return -EFAULT;
} else {
memcpy(target, src, size);
}
return 0;
}

#ifdef CONFIG_PROC_VMCORE_DEVICE_DUMP
static int vmcoredd_copy_dumps(void *dst, u64 start, size_t size, int userbuf)
static int vmcoredd_copy_dumps(struct iov_iter *iter, u64 start, size_t size)
{
struct vmcoredd_node *dump;
u64 offset = 0;
Expand All @@ -279,14 +265,13 @@ static int vmcoredd_copy_dumps(void *dst, u64 start, size_t size, int userbuf)
if (start < offset + dump->size) {
tsz = min(offset + (u64)dump->size - start, (u64)size);
buf = dump->buf + start - offset;
if (copy_to(dst, buf, tsz, userbuf)) {
if (copy_to_iter(buf, tsz, iter) < tsz) {
ret = -EFAULT;
goto out_unlock;
}

size -= tsz;
start += tsz;
dst += tsz;

/* Leave now if buffer filled already */
if (!size)
Expand Down Expand Up @@ -342,33 +327,30 @@ static int vmcoredd_mmap_dumps(struct vm_area_struct *vma, unsigned long dst,
/* Read from the ELF header and then the crash dump. On error, negative value is
* returned otherwise number of bytes read are returned.
*/
static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
int userbuf)
static ssize_t __read_vmcore(struct iov_iter *iter, loff_t *fpos)
{
ssize_t acc = 0, tmp;
size_t tsz;
u64 start;
struct vmcore *m = NULL;

if (buflen == 0 || *fpos >= vmcore_size)
if (iter->count == 0 || *fpos >= vmcore_size)
return 0;

/* trim buflen to not go beyond EOF */
if (buflen > vmcore_size - *fpos)
buflen = vmcore_size - *fpos;
/* trim iter to not go beyond EOF */
if (iter->count > vmcore_size - *fpos)
iter->count = vmcore_size - *fpos;

/* Read ELF core header */
if (*fpos < elfcorebuf_sz) {
tsz = min(elfcorebuf_sz - (size_t)*fpos, buflen);
if (copy_to(buffer, elfcorebuf + *fpos, tsz, userbuf))
tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
if (copy_to_iter(elfcorebuf + *fpos, tsz, iter) < tsz)
return -EFAULT;
buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;

/* leave now if filled buffer already */
if (buflen == 0)
if (iter->count == 0)
return acc;
}

Expand All @@ -389,71 +371,64 @@ static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
/* Read device dumps */
if (*fpos < elfcorebuf_sz + vmcoredd_orig_sz) {
tsz = min(elfcorebuf_sz + vmcoredd_orig_sz -
(size_t)*fpos, buflen);
(size_t)*fpos, iter->count);
start = *fpos - elfcorebuf_sz;
if (vmcoredd_copy_dumps(buffer, start, tsz, userbuf))
if (vmcoredd_copy_dumps(iter, start, tsz))
return -EFAULT;

buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;

/* leave now if filled buffer already */
if (!buflen)
if (!iter->count)
return acc;
}
#endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */

/* Read remaining elf notes */
tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, buflen);
tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
kaddr = elfnotes_buf + *fpos - elfcorebuf_sz - vmcoredd_orig_sz;
if (copy_to(buffer, kaddr, tsz, userbuf))
if (copy_to_iter(kaddr, tsz, iter) < tsz)
return -EFAULT;

buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;

/* leave now if filled buffer already */
if (buflen == 0)
if (iter->count == 0)
return acc;
}

list_for_each_entry(m, &vmcore_list, list) {
if (*fpos < m->offset + m->size) {
tsz = (size_t)min_t(unsigned long long,
m->offset + m->size - *fpos,
buflen);
iter->count);
start = m->paddr + *fpos - m->offset;
tmp = read_from_oldmem(buffer, tsz, &start,
userbuf, cc_platform_has(CC_ATTR_MEM_ENCRYPT));
tmp = read_from_oldmem_iter(iter, tsz, &start,
cc_platform_has(CC_ATTR_MEM_ENCRYPT));
if (tmp < 0)
return tmp;
buflen -= tsz;
*fpos += tsz;
buffer += tsz;
acc += tsz;

/* leave now if filled buffer already */
if (buflen == 0)
if (iter->count == 0)
return acc;
}
}

return acc;
}

static ssize_t read_vmcore(struct file *file, char __user *buffer,
size_t buflen, loff_t *fpos)
static ssize_t read_vmcore(struct kiocb *iocb, struct iov_iter *iter)
{
return __read_vmcore((__force char *) buffer, buflen, fpos, 1);
return __read_vmcore(iter, &iocb->ki_pos);
}

/*
* The vmcore fault handler uses the page cache and fills data using the
* standard __vmcore_read() function.
* standard __read_vmcore() function.
*
* On s390 the fault handler is used for memory regions that can't be mapped
* directly with remap_pfn_range().
Expand All @@ -463,18 +438,22 @@ static vm_fault_t mmap_vmcore_fault(struct vm_fault *vmf)
#ifdef CONFIG_S390
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
pgoff_t index = vmf->pgoff;
struct iov_iter iter;
struct kvec kvec;
struct page *page;
loff_t offset;
char *buf;
int rc;

page = find_or_create_page(mapping, index, GFP_KERNEL);
if (!page)
return VM_FAULT_OOM;
if (!PageUptodate(page)) {
offset = (loff_t) index << PAGE_SHIFT;
buf = __va((page_to_pfn(page) << PAGE_SHIFT));
rc = __read_vmcore(buf, PAGE_SIZE, &offset, 0);
kvec.iov_base = page_address(page);
kvec.iov_len = PAGE_SIZE;
iov_iter_kvec(&iter, READ, &kvec, 1, PAGE_SIZE);

rc = __read_vmcore(&iter, &offset);
if (rc < 0) {
unlock_page(page);
put_page(page);
Expand Down Expand Up @@ -724,7 +703,7 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)

static const struct proc_ops vmcore_proc_ops = {
.proc_open = open_vmcore,
.proc_read = read_vmcore,
.proc_read_iter = read_vmcore,
.proc_lseek = default_llseek,
.proc_mmap = mmap_vmcore,
};
Expand Down

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