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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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