[PATCH 1/3] vmcore: Convert copy_oldmem_page() to take an iov_iter

Matthew Wilcox (Oracle)
2021-12-13T00:06:34Z

Instead of passing in a 'buf' and 'userbuf' argument, pass in an iov_iter.
s390 needs more work to pass the iov_iter down further, or refactor,
but I'd be more comfortable if someone who can test on s390 did that work.

It's more convenient to convert the whole of read_from_oldmem() to
take an iov_iter at the same time, so rename it to read_from_oldmem_iter()
and add a temporary read_from_oldmem() wrapper that creates an iov_iter.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
arch/arm/kernel/crash_dump.c | 14 ++-------
arch/arm64/kernel/crash_dump.c | 14 ++-------
arch/ia64/kernel/crash_dump.c | 12 ++------
arch/mips/kernel/crash_dump.c | 13 ++------
arch/powerpc/kernel/crash_dump.c | 20 +++---------
arch/riscv/kernel/crash_dump.c | 13 ++------
arch/s390/kernel/crash_dump.c | 12 +++++---
arch/sh/kernel/crash_dump.c | 15 +++------
arch/x86/kernel/crash_dump_32.c | 13 ++------
arch/x86/kernel/crash_dump_64.c | 24 ++++++---------
fs/proc/vmcore.c | 53 ++++++++++++++++++++------------
include/linux/crash_dump.h | 9 +++---
12 files changed, 79 insertions(+), 133 deletions(-)

diff --git a/arch/arm/kernel/crash_dump.c b/arch/arm/kernel/crash_dump.c
index 53cb92435392..15d7db782f24 100644
--- a/arch/arm/kernel/crash_dump.c
+++ b/arch/arm/kernel/crash_dump.c
@@ -27,9 +27,8 @@
* @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
* copied or negative error in case of failure.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset,
- int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
void *vaddr;

@@ -40,14 +39,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
if (!vaddr)
return -ENOMEM;

- if (userbuf) {
- if (copy_to_user(buf, vaddr + offset, csize)) {
- iounmap(vaddr);
- return -EFAULT;
- }
- } else {
- memcpy(buf, vaddr + offset, csize);
- }
+ csize = copy_to_iter(vaddr + offset, csize, iter);

iounmap(vaddr);
return csize;
diff --git a/arch/arm64/kernel/crash_dump.c b/arch/arm64/kernel/crash_dump.c
index 58303a9ec32c..991d30aac439 100644
--- a/arch/arm64/kernel/crash_dump.c
+++ b/arch/arm64/kernel/crash_dump.c
@@ -25,9 +25,8 @@
* @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
* copied or negative error in case of failure.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset,
- int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
void *vaddr;

@@ -38,14 +37,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
if (!vaddr)
return -ENOMEM;

- if (userbuf) {
- if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
- memunmap(vaddr);
- return -EFAULT;
- }
- } else {
- memcpy(buf, vaddr + offset, csize);
- }
+ csize = copy_to_iter(vaddr + offset, csize, iter);

memunmap(vaddr);

diff --git a/arch/ia64/kernel/crash_dump.c b/arch/ia64/kernel/crash_dump.c
index 0ed3c3dee4cd..bc331272bbd6 100644
--- a/arch/ia64/kernel/crash_dump.c
+++ b/arch/ia64/kernel/crash_dump.c
@@ -31,21 +31,15 @@
* copying the data to a pre-allocated kernel page and then copying to user
* space in non-atomic context.
*/
-ssize_t
-copy_oldmem_page(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
void *vaddr;

if (!csize)
return 0;
vaddr = __va(pfn<<PAGE_SHIFT);
- if (userbuf) {
- if (copy_to_user(buf, (vaddr + offset), csize)) {
- return -EFAULT;
- }
- } else
- memcpy(buf, (vaddr + offset), csize);
+ csize = copy_to_iter(vaddr + offset, csize, iter);
return csize;
}

diff --git a/arch/mips/kernel/crash_dump.c b/arch/mips/kernel/crash_dump.c
index 2e50f55185a6..926665c798b6 100644
--- a/arch/mips/kernel/crash_dump.c
+++ b/arch/mips/kernel/crash_dump.c
@@ -15,8 +15,8 @@
* Copy a page from "oldmem". For this page, there is no pte mapped
* in the current kernel.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
void *vaddr;

@@ -24,14 +24,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
return 0;

vaddr = kmap_local_pfn(pfn);
-
- if (!userbuf) {
- memcpy(buf, vaddr + offset, csize);
- } else {
- if (copy_to_user(buf, vaddr + offset, csize))
- csize = -EFAULT;
- }
-
+ csize = copy_to_iter(vaddr + offset, csize, iter);
kunmap_local(vaddr);

return csize;
diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index 5693e1c67c2b..541bcc01490c 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -68,18 +68,6 @@ void __init setup_kdump_trampoline(void)
}
#endif /* CONFIG_NONSTATIC_KERNEL */

-static size_t copy_oldmem_vaddr(void *vaddr, char *buf, size_t csize,
- unsigned long offset, int userbuf)
-{
- if (userbuf) {
- if (copy_to_user((char __user *)buf, (vaddr + offset), csize))
- return -EFAULT;
- } else
- memcpy(buf, (vaddr + offset), csize);
-
- return csize;
-}
-
/**
* copy_oldmem_page - copy one page from "oldmem"
* @pfn: page frame number to be copied
@@ -93,8 +81,8 @@ static size_t copy_oldmem_vaddr(void *vaddr, char *buf, size_t csize,
* Copy a page from "oldmem". For this page, there is no pte mapped
* in the current kernel. We stitch up a pte, similar to kmap_atomic.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
void *vaddr;
phys_addr_t paddr;
@@ -107,10 +95,10 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,

if (memblock_is_region_memory(paddr, csize)) {
vaddr = __va(paddr);
- csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+ csize = copy_to_iter(vaddr + offset, csize, iter);
} else {
vaddr = ioremap_cache(paddr, PAGE_SIZE);
- csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+ csize = copy_to_iter(vaddr + offset, csize, iter);
iounmap(vaddr);
}

diff --git a/arch/riscv/kernel/crash_dump.c b/arch/riscv/kernel/crash_dump.c
index 86cc0ada5752..f4dffb8c7eb7 100644
--- a/arch/riscv/kernel/crash_dump.c
+++ b/arch/riscv/kernel/crash_dump.c
@@ -20,9 +20,8 @@
* @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
* copied or negative error in case of failure.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset,
- int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
void *vaddr;

@@ -33,13 +32,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
if (!vaddr)
return -ENOMEM;

- if (userbuf) {
- if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
- memunmap(vaddr);
- return -EFAULT;
- }
- } else
- memcpy(buf, vaddr + offset, csize);
+ csize = copy_to_iter(vaddr + offset, csize, iter);

memunmap(vaddr);
return csize;
diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
index 785d54c9350c..09bf559f2c5b 100644
--- a/arch/s390/kernel/crash_dump.c
+++ b/arch/s390/kernel/crash_dump.c
@@ -214,8 +214,8 @@ static int copy_oldmem_user(void __user *dst, void *src, size_t count)
/*
* Copy one page from "oldmem"
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
- unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
+ unsigned long offset)
{
void *src;
int rc;
@@ -223,10 +223,12 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
if (!csize)
return 0;
src = (void *) (pfn << PAGE_SHIFT) + offset;
- if (userbuf)
- rc = copy_oldmem_user((void __force __user *) buf, src, csize);
+
+ /* XXX: pass the iov_iter down to a common function */
+ if (iter_is_iovec(iter))
+ rc = copy_oldmem_user(iter->iov->iov_base, src, csize);
else
- rc = copy_oldmem_kernel((void *) buf, src, csize);
+ rc = copy_oldmem_kernel(iter->kvec->iov_base, src, csize);
return rc;
}

diff --git a/arch/sh/kernel/crash_dump.c b/arch/sh/kernel/crash_dump.c
index 5b41b59698c1..26081861cb62 100644
--- a/arch/sh/kernel/crash_dump.c
+++ b/arch/sh/kernel/crash_dump.c
@@ -23,8 +23,8 @@
* Copy a page from "oldmem". For this page, there is no pte mapped
* in the current kernel. We stitch up a pte, similar to kmap_atomic.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
void __iomem *vaddr;

@@ -32,15 +32,8 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
return 0;

vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
-
- if (userbuf) {
- if (copy_to_user((void __user *)buf, (vaddr + offset), csize)) {
- iounmap(vaddr);
- return -EFAULT;
- }
- } else
- memcpy(buf, (vaddr + offset), csize);
-
+ csize = copy_to_iter(vaddr + offset, csize, iter);
iounmap(vaddr);
+
return csize;
}
diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c
index 5fcac46aaf6b..23d38ecf5de2 100644
--- a/arch/x86/kernel/crash_dump_32.c
+++ b/arch/x86/kernel/crash_dump_32.c
@@ -42,8 +42,8 @@ static inline bool is_crashed_pfn_valid(unsigned long pfn)
* Copy a page from "oldmem". For this page, there might be no pte mapped
* in the current kernel.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
- unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
+ unsigned long offset)
{
void *vaddr;

@@ -54,14 +54,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
return -EFAULT;

vaddr = kmap_local_pfn(pfn);
-
- if (!userbuf) {
- memcpy(buf, vaddr + offset, csize);
- } else {
- if (copy_to_user(buf, vaddr + offset, csize))
- csize = -EFAULT;
- }
-
+ csize = copy_to_iter(vaddr + offset, csize, iter);
kunmap_local(vaddr);

return csize;
diff --git a/arch/x86/kernel/crash_dump_64.c b/arch/x86/kernel/crash_dump_64.c
index a7f617a3981d..8d91e5f2e14d 100644
--- a/arch/x86/kernel/crash_dump_64.c
+++ b/arch/x86/kernel/crash_dump_64.c
@@ -12,8 +12,8 @@
#include <linux/io.h>
#include <linux/cc_platform.h>

-static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
- unsigned long offset, int userbuf,
+static ssize_t __copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset,
bool encrypted)
{
void *vaddr;
@@ -29,13 +29,7 @@ static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
if (!vaddr)
return -ENOMEM;

- if (userbuf) {
- if (copy_to_user((void __user *)buf, vaddr + offset, csize)) {
- iounmap((void __iomem *)vaddr);
- return -EFAULT;
- }
- } else
- memcpy(buf, vaddr + offset, csize);
+ csize = copy_to_iter(vaddr + offset, csize, iter);

set_iounmap_nonlazy();
iounmap((void __iomem *)vaddr);
@@ -55,10 +49,10 @@ static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
* Copy a page from the old kernel's memory. For this page, there is no pte
* mapped in the current kernel. We stitch up a pte, similar to kmap_atomic.
*/
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
- unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
+ unsigned long offset)
{
- return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, false);
+ return __copy_oldmem_page(iter, pfn, csize, offset, false);
}

/**
@@ -66,10 +60,10 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
* memory with the encryption mask set to accommodate kdump on SME-enabled
* machines.
*/
-ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
- unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page_encrypted(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset)
{
- return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, true);
+ return __copy_oldmem_page(iter, pfn, csize, offset, true);
}

ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 509f85148fee..049bafe9c007 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -132,9 +132,8 @@ static int open_vmcore(struct inode *inode, struct file *file)
}

/* Reads a page from the oldmem device from given offset. */
-ssize_t read_from_oldmem(char *buf, size_t count,
- u64 *ppos, int userbuf,
- bool encrypted)
+ssize_t read_from_oldmem_iter(struct iov_iter *iter, size_t count,
+ u64 *ppos, bool encrypted)
{
unsigned long pfn, offset;
size_t nr_bytes;
@@ -155,29 +154,23 @@ ssize_t read_from_oldmem(char *buf, size_t count,

/* If pfn is not ram, return zeros for sparse dump files */
if (!pfn_is_ram(pfn)) {
- tmp = 0;
- if (!userbuf)
- memset(buf, 0, nr_bytes);
- else if (clear_user(buf, nr_bytes))
- tmp = -EFAULT;
+ tmp = iov_iter_zero(nr_bytes, iter);
} else {
if (encrypted)
- tmp = copy_oldmem_page_encrypted(pfn, buf,
+ tmp = copy_oldmem_page_encrypted(iter, pfn,
nr_bytes,
- offset,
- userbuf);
+ offset);
else
- tmp = copy_oldmem_page(pfn, buf, nr_bytes,
- offset, userbuf);
+ tmp = copy_oldmem_page(iter, pfn, nr_bytes,
+ offset);
}
- if (tmp < 0) {
+ if (tmp < nr_bytes) {
up_read(&vmcore_cb_rwsem);
- return tmp;
+ return -EFAULT;
}

*ppos += nr_bytes;
count -= nr_bytes;
- buf += nr_bytes;
read += nr_bytes;
++pfn;
offset = 0;
@@ -187,6 +180,27 @@ ssize_t read_from_oldmem(char *buf, size_t count,
return read;
}

+ssize_t read_from_oldmem(char *buf, size_t count,
+ u64 *ppos, int userbuf,
+ bool encrypted)
+{
+ struct iov_iter iter;
+ struct iovec iov;
+ struct kvec kvec;
+
+ if (userbuf) {
+ iov.iov_base = (__force void __user *)buf;
+ iov.iov_len = count;
+ iov_iter_init(&iter, READ, &iov, 1, count);
+ } else {
+ kvec.iov_base = buf;
+ kvec.iov_len = count;
+ iov_iter_kvec(&iter, READ, &kvec, 1, count);
+ }
+
+ return read_from_oldmem_iter(&iter, count, ppos, encrypted);
+}
+
/*
* Architectures may override this function to allocate ELF header in 2nd kernel
*/
@@ -231,11 +245,10 @@ int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
/*
* Architectures which support memory encryption override this.
*/
-ssize_t __weak
-copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
- unsigned long offset, int userbuf)
+ssize_t __weak copy_oldmem_page_encrypted(struct iov_iter *iter,
+ unsigned long pfn, size_t csize, unsigned long offset)
{
- return copy_oldmem_page(pfn, buf, csize, offset, userbuf);
+ return copy_oldmem_page(iter, pfn, csize, offset);
}

/*
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 620821549b23..a1cf7d5c03c7 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -24,11 +24,10 @@ extern int remap_oldmem_pfn_range(struct vm_area_struct *vma,
unsigned long from, unsigned long pfn,
unsigned long size, pgprot_t prot);

-extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
- unsigned long, int);
-extern ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf,
- size_t csize, unsigned long offset,
- int userbuf);
+ssize_t copy_oldmem_page(struct iov_iter *i, unsigned long pfn, size_t csize,
+ unsigned long offset);
+ssize_t copy_oldmem_page_encrypted(struct iov_iter *iter, unsigned long pfn,
+ size_t csize, unsigned long offset);

void vmcore_cleanup(void);

--
2.33.0