Longer command line for kexec on i386

Longer command line for kexec on i386

[Ed Swierk]

I'm attempting to get kexec to pass a command line longer than 256 bytes to the
new kernel, using kexec-tools-testing-20070330 and kernel 2.6.22.1.  The new
kernel is a bzImage, and I'm using kexec to tack on a command line and an initrd.

I made the following change to kexec:

--- kexec-tools-testing-20070330.orig/include/x86/x86-linux.h
+++ kexec-tools-testing-20070330/include/x86/x86-linux.h
@@ -148,14 +148,13 @@
 #endif
        struct e820entry e820_map[E820MAX];     /* 0x2d0 */
                                                /* 0x550 */
-#define COMMAND_LINE_SIZE 256
+#define COMMAND_LINE_SIZE 2048
 };

 struct x86_linux_faked_param_header {
        struct x86_linux_param_header hdr;      /* 0x00 */
        uint8_t reserved16[688];                /* 0x550 */
-       uint8_t command_line[COMMAND_LINE_SIZE]; /* 0x800 */
-       uint8_t reserved17[1792];               /* 0x900 - 0x1000 */
+       uint8_t command_line[COMMAND_LINE_SIZE]; /* 0x800 - 0x1000 */
 };

 struct x86_linux_header {

but I'm now seeing intermittent corruption of the initrd in the new kernel--a
few bytes at different locations each time.

I suspect I've neglected some other important changes to the boot protocol.  Any
clues would be appreciated.

Thanks,
--Ed

Re: Longer command line for kexec on i386

[Ed Swierk]

Ed Swierk <eswierk <at> arastra.com> writes:

> I made the following change to kexec:
>
> [deleted]
> 
> but I'm now seeing intermittent corruption of the initrd in the new kernel--a
> few bytes at different locations each time.
> 
> I suspect I've neglected some other important changes to the boot protocol.  

The corruption is due to a "hardware" bug (qemu), which was in fact corrupting
memory (http://article.gmane.org/gmane.comp.emulators.qemu/18774).  Extending
the command line in kexec somehow made the corruption noticeable.

--Ed