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[pxe] Introduce PXE exit hook for NBP chaining 

It might be the case that we wish to chain to an NBP without
being "in the way".  We now implement a hook in our exit path
for gPXE *.*pxe build targets.  The hook is a pointer to a
SEG16:OFF16 which we try to jump to during exit.  By default,
this pointer results in the usual exit path.

We also implement the "pxenv_file_exit_hook" PXE API routine
to allow the user to specify an alternate SEG16:OFF16 to jump
to during exit.

Unfortunately, this additional PXE extension has a cost
in code size.  Fortunately, a look at the size difference
for a gPXE .rom build target shows zero size difference
after compression.

The routine is documented in doc/pxe_extensions as follows:

FILE EXIT HOOK

Op-Code:	PXENV_FILE_EXIT_HOOK (00e7h)

Input:	Far pointer to a t_PXENV_FILE_EXIT_HOOK parameter
		structure that has been initialized by the caller.

Output:	PXENV_EXIT_SUCCESS or PXENV_EXIT_FAILURE must be
		returned in AX.  The Status field in the parameter
		structure must be set to one of the values represented
		by the PXENV_STATUS_xxx constants.

Description:Modify the exit path to jump to the specified code.
		Only valid for pxeprefix-based builds.

typedef struct s_PXENV_FILE_EXIT_HOOK {
        PXENV_STATUS_t Status;
        SEGOFF16_t Hook;
} t_PXENV_FILE_EXIT_HOOK;

Set before calling API service:

Hook:	The SEG16:OFF16 of the code to jump to.

Returned from API service:

Status:	See PXENV_STATUS_xxx constants.

Requested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Shao Miller <shao.miller@yrdsb.edu.on.ca>
Signed-off-by: Marty Connor <mdc@etherboot.org>
This commit is contained in:
Shao Miller 2010-01-23 22:12:27 -05:00 committed by Marty Connor
parent 5efc2fcb60
commit 112a3f2de2
6 changed files with 112 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
src/arch/i386/include/pxe.h
View File

@ -67,6 +67,7 @@ union u_PXENV_ANY {
struct s_PXENV_GET_FILE_SIZE get_file_size;
struct s_PXENV_FILE_EXEC file_exec;
struct s_PXENV_FILE_API_CHECK file_api_check;
struct s_PXENV_FILE_EXIT_HOOK file_exit_hook;
};
typedef union u_PXENV_ANY PXENV_ANY_t;

22
src/arch/i386/include/pxe_api.h
View File

@ -1778,6 +1778,28 @@ extern PXENV_EXIT_t pxenv_file_api_check ( struct s_PXENV_FILE_API_CHECK *file_a
/** @} */ /* pxenv_file_api_check */
/** @defgroup pxenv_file_exit_hook PXENV_FILE_EXIT_HOOK
*
* FILE EXIT HOOK
*
* @{
*/
/** PXE API function code for pxenv_file_exit_hook() */
#define PXENV_FILE_EXIT_HOOK 0x00e7
/** Parameter block for pxenv_file_exit_hook() */
struct s_PXENV_FILE_EXIT_HOOK {
PXENV_STATUS_t Status; /**< PXE status code */
SEGOFF16_t Hook; /**< SEG16:OFF16 to jump to */
} PACKED;
typedef struct s_PXENV_FILE_EXIT_HOOK PXENV_FILE_EXIT_HOOK_t;
extern PXENV_EXIT_t pxenv_file_exit_hook ( struct s_PXENV_FILE_EXIT_HOOK *file_exit_hook );
/** @} */ /* pxenv_file_exit_hook */
/** @} */ /* pxe_file_api */
/** @defgroup pxe_loader_api PXE Loader API

5
src/arch/i386/interface/pxe/pxe_call.c
View File

@ -104,6 +104,7 @@ union pxenv_call {
PXENV_EXIT_t ( * get_file_size ) ( struct s_PXENV_GET_FILE_SIZE * );
PXENV_EXIT_t ( * file_exec ) ( struct s_PXENV_FILE_EXEC * );
PXENV_EXIT_t ( * file_api_check ) ( struct s_PXENV_FILE_API_CHECK * );
PXENV_EXIT_t ( * file_exit_hook ) ( struct s_PXENV_FILE_EXIT_HOOK * );
};
/**
@ -310,6 +311,10 @@ __asmcall void pxe_api_call ( struct i386_all_regs *ix86 ) {
pxenv_call.file_api_check = pxenv_file_api_check;
param_len = sizeof ( pxenv_any.file_api_check );
break;
case PXENV_FILE_EXIT_HOOK:
pxenv_call.file_exit_hook = pxenv_file_exit_hook;
param_len = sizeof ( pxenv_any.file_exit_hook );
break;
default:
DBG ( "PXENV_UNKNOWN_%hx", opcode );
pxenv_call.unknown = pxenv_unknown;

40
src/arch/i386/interface/pxe/pxe_file.c
View File

@ -12,9 +12,12 @@
#include <gpxe/posix_io.h>
#include <gpxe/features.h>
#include <pxe.h>
#include <realmode.h>
/*
* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
* Portions (C) 2010 Shao Miller <shao.miller@yrdsb.edu.on.ca>.
* [PXE exit hook logic]
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
@ -230,6 +233,9 @@ PXENV_EXIT_t pxenv_file_exec ( struct s_PXENV_FILE_EXEC *file_exec ) {
return PXENV_EXIT_SUCCESS;
}
segoff_t __data16 ( pxe_exit_hook ) = { 0, 0 };
#define pxe_exit_hook __use_data16 ( pxe_exit_hook )
/**
* FILE API CHECK
*
@ -260,7 +266,41 @@ PXENV_EXIT_t pxenv_file_api_check ( struct s_PXENV_FILE_API_CHECK *file_api_chec
file_api_check->Magic = 0xe9c17b20;
file_api_check->Provider = 0x45585067; /* "gPXE" */
file_api_check->APIMask = 0x0000007f; /* Functions e0-e6 */
/* Check to see if we have a PXE exit hook */
if ( pxe_exit_hook.segment | pxe_exit_hook.offset )
/* Function e7, also */
file_api_check->APIMask |= 0x00000080;
file_api_check->Flags = 0; /* None defined */
return PXENV_EXIT_SUCCESS;
}
}
/**
* FILE EXIT HOOK
*
* @v file_exit_hook Pointer to a struct
* s_PXENV_FILE_EXIT_HOOK
* @v s_PXENV_FILE_EXIT_HOOK::Hook SEG16:OFF16 to jump to
* @ret #PXENV_EXIT_SUCCESS Successfully set hook
* @ret #PXENV_EXIT_FAILURE We're not an NBP build
* @ret s_PXENV_FILE_EXIT_HOOK::Status PXE status code
*
*/
PXENV_EXIT_t pxenv_file_exit_hook ( struct s_PXENV_FILE_EXIT_HOOK
*file_exit_hook ) {
DBG ( "PXENV_FILE_EXIT_HOOK" );
/* Check to see if we have a PXE exit hook */
if ( pxe_exit_hook.segment | pxe_exit_hook.offset ) {
/* We'll jump to the specified SEG16:OFF16 during exit */
pxe_exit_hook.segment = file_exit_hook->Hook.segment;
pxe_exit_hook.offset = file_exit_hook->Hook.offset;
file_exit_hook->Status = PXENV_STATUS_SUCCESS;
return PXENV_EXIT_SUCCESS;
}
DBG ( " not NBP" );
file_exit_hook->Status = PXENV_STATUS_UNSUPPORTED;
return PXENV_EXIT_FAILURE;
}

12
src/arch/i386/prefix/pxeprefix.S
View File

@ -718,6 +718,13 @@ run_gpxe:
lret
.section ".text16", "ax", @progbits
1:
/* Update the exit hook */
movw %cs,pxe_exit_hook+2
push %ax
mov $2f,%ax
mov %ax,pxe_exit_hook
pop %ax
/* Run main program */
pushl $main
pushw %cs
@ -731,7 +738,10 @@ run_gpxe:
movw %di, %ss
movl %ebp, %esp
/* Check PXE stack magic */
/* Jump to hook if applicable */
ljmpw *pxe_exit_hook
2: /* Check PXE stack magic */
popl %eax
cmpl $STACK_MAGIC, %eax
jne 1f

33
src/doc/pxe_extensions
View File

@ -277,3 +277,36 @@ Provider: Set to 0x45585067 ("gPXE"). Another implementation of this
APIMask: Bitmask of supported API functions (one bit for each function
in the range 00e0h to 00ffh).
Flags: Set to zero, reserved for future use.
FILE EXIT HOOK
Op-Code: PXENV_FILE_EXIT_HOOK (00e7h)
Input: Far pointer to a t_PXENV_FILE_EXIT_HOOK parameter
structure that has been initialized by the caller.
Output: PXENV_EXIT_SUCCESS or PXENV_EXIT_FAILURE must be
returned in AX. The Status field in the parameter
structure must be set to one of the values represented
by the PXENV_STATUS_xxx constants.
Description: Modify the exit path to jump to the specified code.
Only valid for pxeprefix-based builds.
typedef struct s_PXENV_FILE_EXIT_HOOK {
PXENV_STATUS_t Status;
SEGOFF16_t Hook;
} t_PXENV_FILE_EXIT_HOOK;
Set before calling API service:
Hook: The SEG16:OFF16 of the code to jump to.
Returned from API service:
Status: See PXENV_STATUS_xxx constants.