- To reduce confuse rename the parts of linuxbios bios that run from

  ram linuxbios_ram instead of linuxbios_c and linuxbios_payload...
- Reordered the linker sections so the LinuxBIOS fallback image can take more the 64KiB on x86
- ROM_IMAGE_SIZE now will work when it is specified as larger than 64KiB.
- Tweaked the reset16.inc and reset16.lds to move the sanity check to see if everything will work.
- Start using romcc's built in preprocessor (This will simplify header compiler checks)
- Add helper functions for examining all of the resources
- Remove debug strings from chip.h
- Add llshell to src/arch/i386/llshell (Sometime later I can try it...)
- Add the ability to catch exceptions on x86
- Add gdb_stub support to x86
- Removed old cpu options
- Added an option so we can detect movnti support
- Remove some duplicate definitions from pci_ids.h
- Remove the 64bit resource code in amdk8/northbridge.c in preparation for making it generic
- Minor romcc bug fixes


git-svn-id: svn://svn.coreboot.org/coreboot/trunk@1727 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

2 files changed, 905 insertions, 0 deletions

diff --git a/src/arch/i386/llshell/llshell.inc b/src/arch/i386/llshell/llshell.inc
new file mode 100644
index 0000000000..8054a0a6e7
--- /dev/null
+++ b/src/arch/i386/llshell/llshell.inc
@@ -0,0 +1,880 @@
+jmp llshell_out
+
+// (c) 2004 Bryan Chafy,  This program is released under the GPL
+
+// LLShell, A low level interactive debug shell
+// Designed to be an interactive shell that operates with zero
+// system resources.  For example at initial boot.
+
+// to use, jump to label "low_level_shell" 
+// set %esp to the return address for exiting
+
+
+#define UART_BASEADDR $0x3f8  
+#define resultreg %esi
+#define subroutinereg %edi
+#define freqtime $2193  // 1.93 * freq
+#define timertime $6000
+.equ	sys_IOPL, 110		
+
+// .data
+// .text
+
+welcome:
+ 	.string "\r\n! Low Level Shell (LLShell)  (c)2004 Bryan Chafy \r\n\r\n"
+prompt:
+	.string "\r\n!> "
+badcmd:
+ 	.string "bad command\r\n"
+sorry:
+ 	.string "sorry, not yet implemented\r\n"
+cmds:
+       	.string "\r\nList of commands:\r\n \
+\r\nbeep                    -- pc speaker beep \
+\r\nrst (or RST)            -- reset \
+\r\nout(b,w,l) <val> <port> -- raw out val at port \
+\r\nin(b,w,l)  <port>       -- show raw port value \
+\r\njmp  <address>          -- jmp to address (llshell addr is in eax) \
+\r\ncall <address>          -- funcion call (assumes a working stack) \
+\r\ncli                     -- clear interrupts \
+\r\nsti                     -- enable interrupts \
+\r\npush <value>            -- push value onto stack \
+\r\npop                     -- pop from stack and display \
+\r\nwm(b,w,l) <addr> <val>  -- write mem \
+\r\ndm   <addr> <lines>     -- dump mem  \
+\r\nmcp  <src> <dst> <size> -- mem copy  \
+\r\nmpat <pat> <dst> <size> -- mem pattern \
+\r\nmemt <begin> <end>      -- memory test \
+\r\npcir(b,w,l) <loc>       -- pci read config \
+\r\npciw(b,w,l) <loc> <val> -- pci write config  \
+\r\ndl   <addr> <size>      -- memory download (display xor cheksum at completion) \
+\r\ncram <addr> <size>      -- enable cache to be ram (experimental) \
+\r\nbaud <val>              -- change baudrate (not yet implemented)  \
+\r\nexit                    -- exit shell \
+\r\nAll values in hex (0x prefixing ok)  \
+\r\n"
+
+cr:     
+	.string "\r\n"
+spaces:     
+	.string "   "
+
+// .globl _start
+//ASSUME CS:@CODE, DS:@DATA
+
+// _start:
+
+// call ioperms
+
+low_level_shell:
+
+mov $preamble,subroutinereg
+jmp beep
+preamble:
+mov $welcome,resultreg
+mov $readcommand,subroutinereg
+jmp displaystring
+
+readcommand:
+mov $prompt,resultreg
+mov $rcmd,subroutinereg
+jmp displaystring
+
+rcmd:
+mov $readcommand,subroutinereg
+movl $0x0, resultreg
+
+readchar:
+mov  UART_BASEADDR+5,%dx
+in   %dx, %al
+and  $0x9f,%al
+test $0x01,%al
+jz   readchar
+mov  UART_BASEADDR,%dx
+in   %dx,%al             //char in al
+xchg %al,%ah
+
+send_char:
+mov  UART_BASEADDR+5,%dx
+us_wait:
+in   %dx,%al
+test $0x20,%al
+jz us_wait
+mov  UART_BASEADDR,%dx
+xchg %al,%ah
+out  %al,%dx            // output char
+
+cmp  $0x0D,%al      //CR
+jnz  eval_char
+mov  $0x0A,%ah
+jmp  send_char
+
+eval_char:
+cmp  $0x20,%al      //space
+jz   cmdtable
+cmp  $0x0A,%al      //CR
+jz   cmdtable
+cmp  $0x08,%al      //BS
+jnz  additup
+//subit:
+shr  $0x8,resultreg
+jmp  readchar
+additup:
+shl  $0x8,resultreg
+and  $0xff,%eax
+add  %eax,resultreg
+jmp  readchar
+
+cmdtable:
+mov resultreg,%eax
+cmp $0,%eax
+jz  readcommand
+cmp $0x74657374,%eax
+jz  dotest
+cmp $0x68656c70,%eax
+jz  dohelp
+cmp $0x0000003f,%eax
+jz  dohelp
+cmp $0x6f757462,%eax
+jz  dooutb
+cmp $0x6f757477,%eax
+jz  dooutw
+cmp $0x6f75746c,%eax
+jz  dooutd
+cmp $0x00696e62,%eax
+jz doinb
+cmp $0x00696e77,%eax
+jz doinw
+cmp $0x00696e6c,%eax
+jz doind
+cmp $0x63697262,%eax
+jz pcirb
+cmp $0x63697277,%eax
+jz pcirw
+cmp $0x6369726c,%eax
+jz pcirl
+cmp $0x63697762,%eax
+jz pciwb
+cmp $0x63697777,%eax
+jz pciww
+cmp $0x6369776c,%eax
+jz pciwl
+cmp $0x00776d62,%eax
+jz  wmemb
+cmp $0x00776d77,%eax
+jz  wmemw
+cmp $0x00776d6c,%eax
+jz  wmeml
+cmp $0x0000646d,%eax
+jz  dodmem  
+cmp $0x6d656d74,%eax
+jz  memt                    // mem test
+cmp $0x00727374,%eax
+jz  rst                     // reset
+cmp $0x00525354,%eax
+jz  RST
+cmp $0x62656570,%eax
+jz  beep   
+cmp $0x0000646c,%eax
+jz  dodl                    // download to mem <loc> <size>
+cmp $0x006a6d70,%eax
+jz  jmpto                   // jump to location (eax holds return addr)
+cmp $0x62617564,%eax
+jz  baud                    // change baudrate
+cmp $0x00696e74,%eax
+jz  doint                   // trigger an interrupt 
+cmp $0x63616c6c,%eax
+jz  callto                  // call assumes memory
+cmp $0x70757368,%eax
+jz  dopush                  // assumes mem
+cmp $0x00706f70,%eax
+jz  dopop                   // assumes mem
+cmp $0x6372616d,%eax
+jz  cram                    // cache ram trick <location> <size>
+cmp $0x006d6370,%eax
+jz  mcp                     // mem copy <src> <dst> <size>
+cmp $0x6d706174,%eax
+jz  dopattern
+cmp $0x00636c69,%eax
+jz docli
+cmp $0x00737469,%eax
+jz dosti
+cmp $0x65786974,%eax
+jz  doexit
+mov $badcmd,resultreg
+mov $readcommand,subroutinereg
+jmp displaystring
+
+
+readnibbles:
+movl $0x0, resultreg
+readit:
+mov  UART_BASEADDR+5,%dx
+in   %dx, %al
+and  $0x9f,%al
+test $0x1,%al
+jz   readit
+mov  UART_BASEADDR,%dx
+in   %dx,%al
+xchg %al,%ah
+
+sendchar:
+mov  UART_BASEADDR+5,%dx
+us_waitit:
+in   %dx,%al
+test $0x20,%al
+jz   us_waitit
+mov  UART_BASEADDR,%dx
+xchg %al,%ah
+out  %al,%dx            // output char
+
+cmp  $0x78,%al
+jz   readit
+cmp  $0x0D,%al      //CR
+jnz  evalchar
+mov  $0x0A,%ah
+jmp  sendchar
+
+evalchar:
+cmp  $0x20,%al        //space
+jz   gosub
+cmp  $0x0A,%al      //CR
+jz   gosub
+cmp  $0x08,%al      //BS
+jnz  processchar
+//subit:
+shr  $0x04,resultreg
+jmp  readit
+processchar:
+cmp  $0x3A,%al
+jl   subnum
+cmp  $0x47,%al
+jl   subcaps 
+//sublc:
+sub  $0x57,%al
+jmp  additupn
+subcaps:
+sub  $0x37,%al
+jmp  additupn
+subnum:
+sub  $0x30,%al
+additupn:
+shl  $0x04,resultreg
+and  $0xf,%eax
+add  %eax,resultreg
+jmp  readit
+
+gosub:
+jmp  *subroutinereg
+
+//intersubcall
+// eax,edx,esi,edi
+
+// ebx,ecx,ebp,esp(?)
+// ds,es,fs,gs
+
+dotest:
+mov $ramtest,resultreg
+mov $test1a,subroutinereg
+jmp displayhex
+test1a:
+mov $welcome,resultreg
+mov $readcommand,subroutinereg
+jmp displayhex
+
+dodmem:
+
+movl $dmem1a, subroutinereg
+jmp  readnibbles
+dmem1a:
+mov  resultreg,%ebx    // address
+movl $dmem1b, subroutinereg
+jmp  readnibbles
+dmem1b:
+mov  resultreg,%ecx    // length
+
+dmemloop:
+mov %ebx,resultreg
+mov $daddr1,subroutinereg
+jmp displayhex
+daddr1:
+mov $spaces,resultreg
+mov $startshowm,subroutinereg
+jmp displaystring
+
+startshowm:
+mov (%ebx),resultreg
+mov $showm1,subroutinereg
+jmp displayhexlinear
+showm1:
+add $0x04,%ebx
+mov (%ebx),resultreg
+mov $showm2,subroutinereg
+jmp displayhexlinear
+showm2:
+add $0x04,%ebx
+mov (%ebx),resultreg
+mov $showm3,subroutinereg
+jmp displayhexlinear
+showm3:
+add $0x04,%ebx
+mov (%ebx),resultreg
+mov $showa0,subroutinereg
+jmp displayhexlinear
+
+showa0:
+sub $0xC,%ebx
+mov (%ebx),resultreg
+mov $showa1,subroutinereg
+jmp displayasciilinear
+showa1:
+add $0x04,%ebx
+mov (%ebx),resultreg
+mov $showa2,subroutinereg
+jmp displayasciilinear
+showa2:
+add $0x04,%ebx
+mov (%ebx),resultreg
+mov $showa3,subroutinereg
+jmp displayasciilinear
+showa3:
+add $0x04,%ebx
+mov (%ebx),resultreg
+mov $doneshow,subroutinereg
+jmp displayasciilinear
+doneshow:
+mov $cr,resultreg
+mov $doneshow1,subroutinereg
+jmp displaystring
+doneshow1:
+dec %cx
+cmp $0x0,%cx
+jz  exitdmem 
+add $0x04,%ebx
+jmp dmemloop
+exitdmem:
+jmp readcommand
+
+dooutb:
+// out val,port
+movl $outb1a, subroutinereg
+jmp  readnibbles
+outb1a:
+mov  resultreg,%ebx
+movl $outb1b, subroutinereg
+jmp  readnibbles
+outb1b:
+mov  resultreg,%edx
+mov  %ebx,%eax
+out  %al,%dx
+jmp  readcommand
+
+dooutw:
+// out val,port
+movl $outw1a, subroutinereg
+jmp  readnibbles
+outw1a:
+mov  resultreg,%ebx
+movl $outw1b, subroutinereg
+jmp  readnibbles
+outw1b:
+mov  resultreg,%edx
+mov  %ebx,%eax
+out  %ax,%dx
+jmp  readcommand
+
+dooutd:
+// out val,port
+movl $outd1a, subroutinereg
+jmp  readnibbles
+outd1a:
+mov  resultreg,%ebx
+movl $outd1b, subroutinereg
+jmp  readnibbles
+outd1b:
+mov  resultreg,%edx
+mov  %ebx,%eax
+out  %eax,%dx
+jmp  readcommand
+
+wmemb:
+movl $wmemba, subroutinereg
+jmp  readnibbles
+wmemba:
+mov  resultreg,%ebx
+movl $wmembb, subroutinereg
+jmp  readnibbles
+wmembb:
+mov  resultreg,%eax
+mov  %al,(%ebx)
+jmp  readcommand
+
+wmemw:
+movl $wmemwa, subroutinereg
+jmp  readnibbles
+wmemwa:
+mov  resultreg,%ebx
+movl $wmemwb, subroutinereg
+jmp  readnibbles
+wmemwb:
+mov  resultreg,%eax
+mov  %ax,(%ebx)
+jmp  readcommand
+
+wmeml:
+movl $wmemla, subroutinereg
+jmp  readnibbles
+wmemla:
+mov  resultreg,%ebx
+movl $wmemlb, subroutinereg
+jmp  readnibbles
+wmemlb:
+mov  resultreg,%eax
+mov  %eax,(%ebx)
+jmp  readcommand
+
+doinb:
+// in port
+movl $inb1a, subroutinereg
+jmp  readnibbles
+inb1a:
+mov  resultreg,%edx
+mov  $0x0,%eax
+in   %dx,%al
+mov  %eax,resultreg
+mov  $readcommand,subroutinereg
+jmp  displayhex
+
+doinw:
+// in port
+movl $inw1a, subroutinereg
+jmp  readnibbles
+inw1a:
+mov  resultreg,%edx
+mov  $0x0,%eax
+in   %dx,%ax
+mov  %eax,resultreg
+mov  $readcommand,subroutinereg
+jmp  displayhex
+
+doind:
+// in port
+movl $ind1a, subroutinereg
+jmp  readnibbles
+ind1a:
+mov  resultreg,%edx
+in   %dx,%eax
+mov  %eax,resultreg
+mov  $readcommand,subroutinereg
+jmp  displayhex
+
+jmpto:
+movl $jmp1a, subroutinereg
+jmp  readnibbles
+jmp1a:
+mov  $readcommand,%eax
+jmp  *resultreg
+
+callto:
+movl $call1a, subroutinereg
+jmp  readnibbles
+call1a:
+mov  $readcommand,%eax
+call *resultreg
+jmp  readcommand
+
+dopush:
+movl $push1a, subroutinereg
+jmp  readnibbles
+push1a:
+mov  resultreg,%eax
+push %eax
+jmp  readcommand
+
+doint:
+movl $int1a, subroutinereg
+jmp  readnibbles
+int1a:
+mov  resultreg,%eax
+// need to lookup int table? 
+// int  %eax
+jmp  readcommand
+
+doenter:
+//setup stack frame
+
+
+dopop:
+movl $readcommand, subroutinereg
+pop  resultreg
+jmp  displayhex
+
+docli:
+cli
+jmp  readcommand
+
+dosti:
+sti
+jmp  readcommand
+
+
+displaystring:
+// resultreg= pointer to string terminated by \0
+dsloop:
+movb  (resultreg),%ah
+cmp  $0x0, %ah
+jz   displaystringexit
+mov  UART_BASEADDR+5,%dx
+us_waits:
+in   %dx,%al
+test $0x20,%al
+jz us_waits
+mov  UART_BASEADDR,%dx
+xchg %al,%ah
+out  %al,%dx            // output char
+inc  resultreg
+jmp  dsloop
+displaystringexit:
+jmp  *subroutinereg
+
+displayhexlinear:
+mov  resultreg,%eax
+xchg %al,%ah     
+rol  $0x10,%eax
+xchg %al,%ah
+mov  %eax,resultreg
+displayhex:
+rol  $0x10,%ecx
+mov  $0x8,%cx
+dhloop:
+cmp  $0xf,%cl
+je   exitdisplayhex
+rol  $0x04,resultreg
+movl resultreg,%eax
+and  $0xf,%al
+cmp  $0xa,%al
+jl   addnum
+//addcaps
+add $0x37,%al
+jmp  outcharhex
+addnum:
+add  $0x30,%al
+outcharhex:
+xchg %al,%ah
+mov  UART_BASEADDR+5,%dx
+us_waith:
+in   %dx,%al
+test $0x20,%al
+jz us_waith
+mov  UART_BASEADDR,%dx
+xchg %al,%ah
+out  %al,%dx            // output char
+dec  %cx
+cmp  $0x0,%cx
+jne  dhloop
+mov  $0x20,%al
+mov  $0x10,%cl
+jmp  outcharhex
+exitdisplayhex:
+rol  $0x10,%ecx
+jmp  *subroutinereg
+
+displayasciilinear:
+mov  resultreg,%eax
+xchg %al,%ah     
+rol  $0x10,%eax
+xchg %al,%ah
+mov  %eax,resultreg
+displayascii:
+rol  $0x10,%ecx
+mov  $0x4,%cx
+daloop:
+rol  $0x08,resultreg
+movl resultreg,%eax
+cmp  $0x7e,%al
+jg   unprintable
+cmp  $0x20,%al
+jl   unprintable
+jmp  outcharascii
+unprintable:
+mov  $0x2e,%al          // dot
+outcharascii:
+xchg %al,%ah
+mov  UART_BASEADDR+5,%dx
+us_waita:
+in   %dx,%al
+test $0x20,%al
+jz us_waita
+mov  UART_BASEADDR,%dx
+xchg %al,%ah
+out  %al,%dx            // output char
+dec  %cx
+cmp  $0x0,%cx
+jne  daloop
+rol  $0x10,%ecx
+jmp  *subroutinereg
+
+rst:
+cli
+movb $0x0fe,%al
+out  %al,$0x64
+hlt
+
+RST:
+cli
+lidt %cs:0x03fff
+int  $0x3
+hlt
+
+
+beep:
+mov  timertime,%eax
+rol  $0x10,%eax
+mov  $0xb6,%al
+out  %al,$0x43
+mov  freqtime,%ax
+out  %al,$0x42
+xchg %al,%ah
+out  %al,$0x42
+
+in   $0x61,%al
+or   $0x03,%al
+out  %al,$0x61
+
+//timer here
+timer:
+in   $0x42,%al
+// xchg %al,%ah
+in   $0x42,%al
+// xchg %al,%ah
+cmp  $0x0,%al
+jnz  timer
+rol  $0x10,%eax
+dec  %ax
+cmp  $0x0,%ax;
+rol  $0x10,%eax
+jnz  timer
+// timer
+
+in   $0x61,%al
+and  $0xfc,%al
+out  %al,$0x61
+jmp  *subroutinereg
+
+dohelp:
+mov $cmds,resultreg
+mov $readcommand,subroutinereg
+jmp displaystring
+
+memt:
+movl $memt1, subroutinereg
+jmp  readnibbles
+memt1:
+mov  resultreg,%ecx
+movl $memt2, subroutinereg
+jmp  readnibbles
+memt2:
+mov  resultreg,%ebx
+xchg %ecx,%eax
+mov  $readcommand,%esp   // internal to linux bios
+jmp ramtest
+
+pcirb:
+movl $pcirb1, subroutinereg
+jmp  readnibbles
+pcirb1:
+mov  resultreg,%eax
+PCI_READ_CONFIG_BYTE
+and  $0xff,%eax
+mov  %eax,resultreg
+mov  $readcommand,subroutinereg
+jmp  displayhex
+
+pcirw:
+movl $pcirw1, subroutinereg
+jmp  readnibbles
+pcirw1:
+mov  resultreg,%eax
+PCI_READ_CONFIG_WORD
+and  $0xffff,%eax
+mov  %eax,resultreg
+mov  $readcommand,subroutinereg
+jmp  displayhex
+
+pcirl:
+movl $pcirl1, subroutinereg
+jmp  readnibbles
+pcirl1:
+mov  resultreg,%eax
+PCI_READ_CONFIG_DWORD
+mov  %eax,resultreg
+mov  $readcommand,subroutinereg
+jmp  displayhex
+
+
+
+
+pciwb:
+movl $pciwb1, subroutinereg
+jmp  readnibbles
+pciwb1:
+mov  resultreg,%ebx
+movl $pciwb2, subroutinereg
+jmp  readnibbles
+pciwb2:
+mov  resultreg,%edx
+mov  %ebx,%eax
+PCI_WRITE_CONFIG_BYTE
+jmp  readcommand
+
+pciww:
+movl $pciww1, subroutinereg
+jmp  readnibbles
+pciww1:
+mov  resultreg,%ebx
+movl $pciww2, subroutinereg
+jmp  readnibbles
+pciww2:
+mov  resultreg,%ecx
+mov  %ebx,%eax
+PCI_WRITE_CONFIG_WORD
+jmp  readcommand
+
+pciwl:
+movl $pciwl1, subroutinereg
+jmp  readnibbles
+pciwl1:
+mov  resultreg,%ebx
+movl $pciwl2, subroutinereg
+jmp  readnibbles
+pciwl2:
+mov  resultreg,%ecx
+mov  %ebx,%eax
+PCI_WRITE_CONFIG_DWORD
+jmp  readcommand
+
+cram:
+//likely not working.  Just testing for now
+movl $cram1, subroutinereg
+jmp  readnibbles
+cram1:
+mov resultreg,%ebx
+movl $cram1, subroutinereg
+jmp  readnibbles
+cram2:
+mov resultreg,%ecx
+// enable it
+mov %cr0,%eax
+and $0x9fffffff,%eax  // also try 0x0fff, 0x2ff(write back)...
+mov %eax,%cr0
+//wbinvd ??
+cacheloop:
+mov (%ebx),%eax
+inc %ebx
+loop cacheloop
+// disable it
+mov %cr0,%eax
+or  $0x60000000,%eax
+mov %eax,%cr0
+//wbinvd ??
+
+dodl:
+movl $dl1, subroutinereg
+jmp  readnibbles
+dl1:
+mov  resultreg,%ebx
+movl $dl2, subroutinereg
+jmp  readnibbles
+dl2:
+mov  resultreg,%ecx
+mov  resultreg,subroutinereg
+mov  %ebx,resultreg
+dlloop:
+mov  UART_BASEADDR+5,%dx
+in   %dx, %al
+and  $0x9f,%al
+test $0x01,%al
+jz   dlloop
+mov  UART_BASEADDR,%dx
+in   %dx,%al
+mov  %al,(%ebx)
+inc  %ebx
+loop dlloop
+csum:
+mov subroutinereg,%ecx
+shr $0x02,%ecx
+mov resultreg,%ebx
+mov $0x0,%eax
+csumloop:
+rol $0x03,%eax
+mov (%ebx),%dl
+xor  %dl,%al
+inc  %ebx
+loop csumloop
+mov $readcommand,subroutinereg
+mov %eax,resultreg
+jmp displayhex
+
+baud:
+mov $sorry,resultreg
+mov $readcommand,subroutinereg
+jmp displaystring
+
+mcp:
+movl $mcp1, subroutinereg
+jmp  readnibbles
+mcp1:
+mov  resultreg,%ebx
+movl $mcp2, subroutinereg
+jmp  readnibbles
+mcp2:
+mov  resultreg,%ecx
+movl $mcp3, subroutinereg
+jmp  readnibbles
+mcp3:
+mov  resultreg,%eax
+xchg %ecx,%eax
+mcploop:
+mov  (%ebx),%dl
+mov  %dl,(%eax)
+inc  %ebx
+inc  %eax
+loop mcploop
+jmp  readcommand
+
+dopattern:
+movl $pat1, subroutinereg
+jmp  readnibbles
+pat1:
+mov  resultreg,%ebx
+movl $pat2, subroutinereg
+jmp  readnibbles
+pat2:
+mov  resultreg,%ecx
+movl $pat3, subroutinereg
+jmp  readnibbles
+pat3:
+mov  resultreg,%eax
+xchg %ecx,%eax
+patloop:
+rol $0x08,%ebx
+mov %bl,(%eax)
+inc %eax
+loop patloop
+jmp readcommand
+
+
+doexit:
+         // LB specific:
+RETSP    // if there's no stack yet, caller must set %esp manually
+// RET_LABEL(low_level_shell)
+
+
+//Linux OS Specific
+ioperms:
+movl	$sys_IOPL, %eax		# system-call ID-number
+movl	$3, %ebx		# new value for IO0PL
+int	$0x80			# enter the kernel
+ret
+
+llshell_out:
diff --git a/src/arch/i386/llshell/readme.linuxbios b/src/arch/i386/llshell/readme.linuxbios
new file mode 100644
index 0000000000..fb23d1a9d4
--- /dev/null
+++ b/src/arch/i386/llshell/readme.linuxbios
@@ -0,0 +1,25 @@
+
+1) Include llshell.inc in your northbridge Config file
+2) In raminit.inc (or whatever), make a jmp out to low_level_shell, setting
+   a return label in %esp.
+For example:
+ram_set_registers:
+
+	mov $llshell_ret1,%esp
+	jmp low_level_shell
+llshell_ret1:
+
+        /* Disable and invalidate the cache */
+        invd
+        mov %cr0, %eax
+        ....
+3) Optionally, comment out two lines in ramtest.inc:
+5:
+        CONSOLE_INFO_TX_STRING($rt_toomany)
+        // intel_chip_post_macro(0xf1)
+        // jmp  .Lhlt
+otherwise, a ramtest failure will hang
+
+4) build and flash as normal
+If it worked, the speaker will beep, and you'll get a shell.
+Type help or ? at the prompt for a list of commands.