Revert lguest magic and use hook in head.S

Version 2.07 of the boot protocol uses 0x23C for the hardware_subarch
field, that for lguest is "1".  This allows us to use the standard
boot entry point rather than the "GenuineLguest" string hack.

The standard entry point also clears the BSS and copies the boot parameters
and commandline for us, saving more code.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 5 insertions, 29 deletions

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 495e46a1f111..d2235db4085f 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -928,18 +928,8 @@ static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
 /*G:030 Once we get to lguest_init(), we know we're a Guest.  The pv_ops
  * structures in the kernel provide points for (almost) every routine we have
  * to override to avoid privileged instructions. */
-__init void lguest_init(void *boot)
+__init void lguest_init(void)
 {
-        /* Copy boot parameters first: the Launcher put the physical location
-         * in %esi, and head.S converted that to a virtual address and handed
-         * it to us.  We use "__memcpy" because "memcpy" sometimes tries to do
-         * tricky things to go faster, and we're not ready for that. */
-        __memcpy(&boot_params, boot, PARAM_SIZE);
-        /* The boot parameters also tell us where the command-line is: save
-         * that, too. */
-        __memcpy(boot_command_line, __va(boot_params.hdr.cmd_line_ptr),
-               COMMAND_LINE_SIZE);
-
         /* We're under lguest, paravirt is enabled, and we're running at
          * privilege level 1, not 0 as normal. */
         pv_info.name = "lguest";
@@ -1024,11 +1014,6 @@ __init void lguest_init(void *boot)
          * the normal data segment to get through booting. */
         asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");
 
-        /* Clear the part of the kernel data which is expected to be zero.
-         * Normally it will be anyway, but if we're loading from a bzImage with
-         * CONFIG_RELOCATALE=y, the relocations will be sitting here. */
-        memset(__bss_start, 0, __bss_stop - __bss_start);
-
         /* The Host uses the top of the Guest's virtual address space for the
          * Host<->Guest Switcher, and it tells us how much it needs in
          * lguest_data.reserve_mem, set up on the LGUEST_INIT hypercall. */
diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S
index ba4282eba5bf..ebc6ac733899 100644
--- a/arch/x86/lguest/i386_head.S
+++ b/arch/x86/lguest/i386_head.S
@@ -5,11 +5,8 @@
 #include <asm/thread_info.h>
 #include <asm/processor-flags.h>
 
-/*G:020 This is where we begin: we have a magic signature which the launcher
- * looks for.  The plan is that the Linux boot protocol will be extended with a
- * "platform type" field which will guide us here from the normal entry point,
- * but for the moment this suffices.  The normal boot code uses %esi for the
- * boot header, so we do too.
+/*G:020 This is where we begin: head.S notes that the boot header's platform
+ * type field is "1" (lguest), so calls us here.  The boot header is in %esi.
  *
  * WARNING: be very careful here!  We're running at addresses equal to physical
  * addesses (around 0), not above PAGE_OFFSET as most code expectes
@@ -19,19 +16,14 @@
  * The .section line puts this code in .init.text so it will be discarded after
  * boot. */
 .section .init.text, "ax", @progbits
-.ascii "GenuineLguest"
+ENTRY(lguest_entry)
         /* Make initial hypercall now, so we can set up the pagetables. */
         movl $LHCALL_LGUEST_INIT, %eax
         movl $lguest_data - __PAGE_OFFSET, %edx
         int $LGUEST_TRAP_ENTRY
 
-        /* Set up boot information pointer to hand to lguest_init(): it wants
-         * a virtual address. */
-        movl %esi, %eax
-        addl $__PAGE_OFFSET, %eax
-
         /* The Host put the toplevel pagetable in lguest_data.pgdir.  The movsl
-         * instruction uses %esi, so we needed to save it above. */
+         * instruction uses %esi implicitly. */
         movl lguest_data - __PAGE_OFFSET + LGUEST_DATA_pgdir, %esi
 
         /* Copy first 32 entries of page directory to __PAGE_OFFSET entries.
@@ -47,7 +39,6 @@
         /* Set up the initial stack so we can run C code. */
         movl $(init_thread_union+THREAD_SIZE),%esp
 
-
         /* Jumps are relative, and we're running __PAGE_OFFSET too low at the
          * moment. */
         jmp lguest_init+__PAGE_OFFSET