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    SubjectRe: [PATCH] Fix mmap_kmem (was: [question] What's the difference between /dev/kmem and /dev/mem)
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    On Sat, 2005-08-13 at 09:56 -0700, Linus Torvalds wrote:
    >
    > On Sat, 13 Aug 2005, Arjan van de Ven wrote:
    > > >
    > > > So I'd be perfectly happy to fix this, but I'd be even happier if we made
    > > > the whole kmem thing a config variable (maybe even default it to "off").
    > >
    > > attached is a simple patch that does exactly this...
    >
    > Well, you should have fixed the bug that Steven had at the same time. Now
    > his patch won't even apply any more, I suspect ;)

    Patch is forgiving ;)

    attached is the same patch but now with Steven's change made as well

    diff -purN linux-before/drivers/char/Kconfig linux-2.6.12/drivers/char/Kconfig
    --- linux-before/drivers/char/Kconfig 2005-08-13 18:38:11.210821000 +0200
    +++ linux-2.6.12/drivers/char/Kconfig 2005-08-13 18:44:31.182935339 +0200
    @@ -1000,6 +1000,12 @@ config MMTIMER
    The mmtimer device allows direct userspace access to the
    Altix system timer.

    +config DEVKMEM
    + tristate "Userspace access to virtual kernel memory (/dev/kmem)"
    + help
    + The /dev/kmem device allows userspace access to kernel virtual
    + memory, which can be useful for kernel debugging.
    +
    source "drivers/char/tpm/Kconfig"

    endmenu
    diff -purN linux-before/drivers/char/mem.c linux-2.6.12/drivers/char/mem.c
    --- linux-before/drivers/char/mem.c 2005-08-13 18:38:11.261815000 +0200
    +++ linux-2.6.12/drivers/char/mem.c 2005-08-13 18:41:09.002351297 +0200
    @@ -259,22 +259,6 @@ static int mmap_mem(struct file * file,
    return 0;
    }

    -static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
    -{
    - unsigned long long val;
    - /*
    - * RED-PEN: on some architectures there is more mapped memory
    - * than available in mem_map which pfn_valid checks
    - * for. Perhaps should add a new macro here.
    - *
    - * RED-PEN: vmalloc is not supported right now.
    - */
    - if (!pfn_valid(vma->vm_pgoff))
    - return -EIO;
    - val = (u64)vma->vm_pgoff << PAGE_SHIFT;
    - vma->vm_pgoff = __pa(val) >> PAGE_SHIFT;
    - return mmap_mem(file, vma);
    -}

    #ifdef CONFIG_CRASH_DUMP
    /*
    @@ -313,6 +297,25 @@ static ssize_t read_oldmem(struct file *
    extern long vread(char *buf, char *addr, unsigned long count);
    extern long vwrite(char *buf, char *addr, unsigned long count);

    +#ifdef CONFIG_DEVKMEM
    +
    +static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
    +{
    + unsigned long long val;
    + /*
    + * RED-PEN: on some architectures there is more mapped memory
    + * than available in mem_map which pfn_valid checks
    + * for. Perhaps should add a new macro here.
    + *
    + * RED-PEN: vmalloc is not supported right now.
    + */
    + val = (u64)vma->vm_pgoff << PAGE_SHIFT;
    + vma->vm_pgoff = __pa(val) >> PAGE_SHIFT;
    + if (!pfn_valid(vma->vm_pgoff))
    + return -EIO;
    + return mmap_mem(file, vma);
    +}
    +
    /*
    * This function reads the *virtual* memory as seen by the kernel.
    */
    @@ -521,6 +524,8 @@ static ssize_t write_kmem(struct file *
    return virtr + wrote;
    }

    +#endif
    +
    #if (defined(CONFIG_ISA) || !defined(__mc68000__)) && (!defined(CONFIG_PPC_ISERIES) || defined(CONFIG_PCI))
    static ssize_t read_port(struct file * file, char __user * buf,
    size_t count, loff_t *ppos)
    @@ -768,6 +773,7 @@ static struct file_operations mem_fops =
    .open = open_mem,
    };

    +#ifdef CONFIG_DEVKMEM
    static struct file_operations kmem_fops = {
    .llseek = memory_lseek,
    .read = read_kmem,
    @@ -775,6 +781,7 @@ static struct file_operations kmem_fops
    .mmap = mmap_kmem,
    .open = open_kmem,
    };
    +#endif

    static struct file_operations null_fops = {
    .llseek = null_lseek,
    @@ -843,9 +850,11 @@ static int memory_open(struct inode * in
    case 1:
    filp->f_op = &mem_fops;
    break;
    +#ifdef CONFIG_DEVKMEM
    case 2:
    filp->f_op = &kmem_fops;
    break;
    +#endif
    case 3:
    filp->f_op = &null_fops;
    break;
    @@ -894,7 +903,9 @@ static const struct {
    struct file_operations *fops;
    } devlist[] = { /* list of minor devices */
    {1, "mem", S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
    +#ifdef CONFIG_DEVKMEM
    {2, "kmem", S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
    +#endif
    {3, "null", S_IRUGO | S_IWUGO, &null_fops},
    #if (defined(CONFIG_ISA) || !defined(__mc68000__)) && (!defined(CONFIG_PPC_ISERIES) || defined(CONFIG_PCI))
    {4, "port", S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
    \
     
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      Last update: 2005-08-13 19:28    [W:0.030 / U:1.040 seconds]
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