[PATCH v8 3/7] kexec, x86: clean boot_params area for entry-32bit path

[Yinghai Lu]

On Wed, Jan 30, 2013 at 1:34 PM, H. Peter Anvin <hpa at zytor.com> wrote:
> On 01/30/2013 01:25 PM, Yinghai Lu wrote:
>>
>> +static void clean_boot_params(unsigned char *real_mode, unsigned long size)
>> +{
>> +     unsigned long end;
>> +
>> +     /* clear value before header */
>> +     memset(real_mode, 0, 0x1f1);
>> +     /* clear value after setup_header  */
>> +     end = *(real_mode + 0x201);
>
> real_mode[0x201] might be clearer...
>
>> +     end += 0x202;
>> +     if (end < size)
>> +             memset(real_mode + end, 0, size - end);
>> +}
>
> You don't actually need the test... the value is inherently smaller than
> 0x301 which is less than the size.
>
> That being said, if you want to sanity-check it you can check that the
> value is in a sensible range -- the permitted range is 0x22 to 0x7f
> inclusive, corresponding to a total end value of 0x224 to 0x281.

yes.

how about clear all and copy only setup_header?

that looks more readable.

Index: kexec-tools/kexec/arch/i386/kexec-bzImage.c
===================================================================
--- kexec-tools.orig/kexec/arch/i386/kexec-bzImage.c
+++ kexec-tools/kexec/arch/i386/kexec-bzImage.c
@@ -211,7 +211,16 @@ int do_bzImage_load(struct kexec_info *i
        /* The argument/parameter segment */
        setup_size = kern16_size + command_line_len + PURGATORY_CMDLINE_SIZE;
        real_mode = xmalloc(setup_size);
-       memcpy(real_mode, kernel, kern16_size);
+       if (!real_mode_entry) {
+               unsigned long size = kernel[0x201] + 0x202 - 0x1f1;
+
+               /* only copy setup_header */
+               memset(real_mode, 0, setup_size);
+               if (size > 0x7f)
+                       size = 0x7f;
+               memcpy(real_mode + 0x1f1, kernel + 0x1f1, size);
+       } else
+               memcpy(real_mode, kernel, kern16_size);

        if (info->kexec_flags & (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT)) {
                /* If using bzImage for capture kernel, then we will not be