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Subject[patch v2 08/10] s390: Add real memory access functions
From: Michael Holzheu <holzheu@linux.vnet.ibm.com>

Add access function for real memory needed by s390 kdump backend.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
---
arch/s390/include/asm/system.h | 2 +
arch/s390/mm/maccess.c | 57 +++++++++++++++++++++++++++++++++++++++++
drivers/s390/char/zcore.c | 20 +-------------
3 files changed, 61 insertions(+), 18 deletions(-)
--- a/arch/s390/include/asm/system.h
+++ b/arch/s390/include/asm/system.h
@@ -114,6 +114,8 @@ extern void pfault_fini(void);
extern void cmma_init(void);
extern int memcpy_real(void *, void *, size_t);
extern void copy_to_absolute_zero(void *dest, void *src, size_t count);
+extern int copy_to_user_real(void __user *dest, void *src, size_t count);
+extern int copy_from_user_real(void *dest, void __user *src, size_t count);

#define finish_arch_switch(prev) do { \
set_fs(current->thread.mm_segment); \
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -11,6 +11,7 @@
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
+#include <linux/gfp.h>
#include <asm/system.h>

/*
@@ -60,6 +61,9 @@ long probe_kernel_write(void *dst, const
return copied < 0 ? -EFAULT : 0;
}

+/*
+ * Copy memory in real mode (kernel to kernel)
+ */
int memcpy_real(void *dest, void *src, size_t count)
{
register unsigned long _dest asm("2") = (unsigned long) dest;
@@ -101,3 +105,56 @@ void copy_to_absolute_zero(void *dest, v
__ctl_load(cr0, 0, 0);
preempt_enable();
}
+
+/*
+ * Copy memory from kernel (real) to user (virtual)
+ */
+int copy_to_user_real(void __user *dest, void *src, size_t count)
+{
+ int offs = 0, size, rc;
+ char *buf;
+
+ buf = (char *) __get_free_page(GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+ rc = -EFAULT;
+ while (offs < count) {
+ size = min(PAGE_SIZE, count - offs);
+ if (memcpy_real(buf, src + offs, size))
+ goto out;
+ if (copy_to_user(dest + offs, buf, size))
+ goto out;
+ offs += size;
+ }
+ rc = 0;
+out:
+ free_page((unsigned long) buf);
+ return rc;
+}
+
+/*
+ * Copy memory from user (virtual) to kernel (real)
+ */
+int copy_from_user_real(void *dest, void __user *src, size_t count)
+{
+ int offs = 0, size, rc;
+ char *buf;
+
+ buf = (char *) __get_free_page(GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+ rc = -EFAULT;
+ while (offs < count) {
+ size = min(PAGE_SIZE, count - offs);
+ if (copy_from_user(buf, src + offs, size))
+ goto out;
+ if (memcpy_real(dest + offs, buf, size))
+ goto out;
+ offs += size;
+ }
+ rc = 0;
+out:
+ free_page((unsigned long) buf);
+ return rc;
+}
+
--- a/drivers/s390/char/zcore.c
+++ b/drivers/s390/char/zcore.c
@@ -142,22 +142,6 @@ static int memcpy_hsa_kernel(void *dest,
return memcpy_hsa(dest, src, count, TO_KERNEL);
}

-static int memcpy_real_user(void __user *dest, unsigned long src, size_t count)
-{
- static char buf[4096];
- int offs = 0, size;
-
- while (offs < count) {
- size = min(sizeof(buf), count - offs);
- if (memcpy_real(buf, (void *) src + offs, size))
- return -EFAULT;
- if (copy_to_user(dest + offs, buf, size))
- return -EFAULT;
- offs += size;
- }
- return 0;
-}
-
static int __init init_cpu_info(enum arch_id arch)
{
struct save_area *sa;
@@ -346,8 +330,8 @@ static ssize_t zcore_read(struct file *f

/* Copy from real mem */
size = count - mem_offs - hdr_count;
- rc = memcpy_real_user(buf + hdr_count + mem_offs, mem_start + mem_offs,
- size);
+ rc = copy_to_user_real(buf + hdr_count + mem_offs,
+ (void *) mem_start + mem_offs, size);
if (rc)
goto fail;



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