[SeaBIOS] [PATCH v2 00/19] SeaBIOS as Compatibility Support Module for UEFI/OVMF

[David Woodhouse]

On Tue, 2013-02-05 at 23:14 -0500, Kevin O'Connor wrote:
> I think the reloc_init() change that I wrote (patch 1) may have been a
> mistake because of the VISIBLE32INIT proliferation that it causes.  I
> put together an alternate approach which requires csm_return().

Hm, there is strangeness here.

I disabled CONFIG_RELOCATE_INIT, and I made the Lock call in OVMF's
LegacyRegion code a no-op so it's never actually locking it; just to
eliminate certain classes of problem.

I also fixed your code as follows:

commit debcd72c34a6b8eba91c9157b15422d418fe8868
Author: David Woodhouse <David.Woodhouse at intel.com>
Date:   Wed Feb 6 13:25:34 2013 +0000

    Fix handle_csm invocation to compensate for BUILD_BIOS_ADDR
    
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>

diff --git a/src/csm.c b/src/csm.c
index 473d322..91a1a57 100644
--- a/src/csm.c
+++ b/src/csm.c
@@ -49,7 +49,8 @@ csm_maininit(struct bregs *regs)
     regs->ax = 0;
 
     // Return directly to UEFI instead of unwinding stack.
-    csm_return(regs);
+    if (CONFIG_RELOCATE_INIT)
+        csm_return(regs);
 }
 
 /* Legacy16InitializeYourself */
diff --git a/src/romlayout.S b/src/romlayout.S
index 07d1645..cbe6b1c 100644
--- a/src/romlayout.S
+++ b/src/romlayout.S
@@ -385,7 +385,6 @@ entry_elf:
         .code16gcc
 
         EXPORTFUNC entry_csm
-        .global csm_return
 entry_csm:
         // Backup register state
         pushfw
@@ -405,15 +404,16 @@ entry_csm:
         movw %ax, %ss
         movl $BUILD_STACK_ADDR, %esp
 
-        // Jump to 32bit mode and call handle_csm32(bregs)
+        // Jump to 32bit mode and call handle_csm(bregs)
         movl $(1f + BUILD_BIOS_ADDR), %edx
         jmp transition32
         .code32
 1:      movl %ebx, %eax
-        calll _cfunc32flat_handle_csm
+        calll _cfunc32flat_handle_csm - BUILD_BIOS_ADDR
         movl $2f, %edx
         jmp transition16big
 
+        .global csm_return
 csm_return:
         movl %eax, %ebx
         movl $2f, %edx

It kind of works. Sometimes. But other times it just locks up in OVMF code at...

handle_csm16 regs 0x0004ffd4 AX=0001
Legacy16UpdateBbs table 480a:0008
MajorVersion 0000
MinorVersion 0000
AcpiTable 00000000
SmbiosTable 00000000
SmbiosTableLength 00000000
DevicePathType 0000
PciIrqMask 0000
NumberE820Entries 0000000c
NumberBbsEntries 00000100
BBsTable 0004a1ea
SmmTable 00000000
OsMemoryAbove1Mb 07a15000
UnconventionalDeviceTable 00000000
handle_csm16 returning AX=0000
enter handle_15:
   a=00002401  b=00000008  c=00000000  d=00000003 ds=0000 es=480a ss=4000
  si=00000000 di=00000000 bp=00000000 sp=0000ffc6 cs=4f00 ip=0030  f=3002
Buffer: EFI DVD/CDROM
Select Item: 0x19

This is most easily reproduced by pressing a key to enter the boot menu.
And if I add '-d in_asm' or '-enable-kvm' to the qemu command line it's
a lot *less* likely to trigger. I don't think I've *ever* seen it with
KVM enabled in fact... but remember, the whole region should be
*unlocked* so I don't know why.

If I then revert romlayout.S to the version I had in my tree (which
obviously won't work with CONFIG_RELOCATE_INIT but as I said, I turned
that off), everything works fine.

I'm using qemu-system-x86_64 v1.3.0 (the Fedora package).


-- 
dwmw2

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