Huang, Ying wrote:
This patchset defines a 32-bit boot protocol for x86 platform,
adds an extensible boot parameter passing mechanism, export the boot
parameters via sysfs.
The patchset has been tested against kernel of git version
v2.6.23-6623-g55b70a0 on x86_64 and i386.
Hi Huang,
This patchset should be rebased on top of Rusty's changes; the rebase is
fairly trivial and I was originally intending to simply commit the
rebase as-is, with the boot protocol version bumped to 2.08.
However, the documentation section is simply wrong in a number of
places. In particular:
+In 32-bit boot protocol, the first step in loading a Linux kernel
+should still be to load the real-mode code and then examine the kernel
+header at offset 0x01f1. But, it is not necessary to load all
+real-mode code, just first 4K bytes traditionally known as "zero page"
+is needed.
This is incorrect. The zeropage (which really is better referred to as
struct boot_param) should be initialized to all zero, except for the
setup header (starting at offset 0x1f0 or 0x1f1(*)) to the length
specified either by boot protocol version or by the byte at offset 0x201.
+At entry, the CPU must be in 32-bit protected mode with paging
+disabled; the CS and DS must be 4G flat segments; %esi holds the base
+address of the "zero page"; %esp, %ebp, %edi should be zero.
You also need to have a GDT loaded with the selectors for __BOOT_CS
(0x10) and __BOOT_DS (0x18) containing appropriate values, and you
should enter with interrupts disabled. For safety, set up ES and SS as
well as DS.
The bit about %esp, %ebp and %edi being zero is nonsense, although
specifying at least %ebp == %edi == 0 for future use isn't a bad idea.
On the other hand, %ebx *is* supposed to be zero.
The documentation in zero-page.txt is wrong when it comes to protocol
versions. Most of these fields are ancient, and only a handful of the
remainder can be tied to specific protocol versions.
+ struct setup_data {
+ u64 next;
+ u32 type;
+ u32 len;
+ u8 data[0];
+ } __attribute__((packed));
Why packed?
Time permitting, I might rewrite this myself, but it may be quicker for
you to update it.
-hpa
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