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#ifndef REALMODE_H
#define REALMODE_H
#include <stdint.h>
#include <registers.h>
#include <ipxe/uaccess.h>
/*
* Data structures and type definitions
*
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
/*
* Declaration of variables in .data16
*
* To place a variable in the .data16 segment, declare it using the
* pattern:
*
* int __data16 ( foo );
* #define foo __use_data16 ( foo );
*
* extern uint32_t __data16 ( bar );
* #define bar __use_data16 ( bar );
*
* static long __data16 ( baz ) = 0xff000000UL;
* #define baz __use_data16 ( baz );
*
* i.e. take a normal declaration, add __data16() around the variable
* name, and add a line saying "#define <name> __use_data16 ( <name> )
*
* You can then access them just like any other variable, for example
*
* int x = foo + bar;
*
* This magic is achieved at a cost of only around 7 extra bytes per
* group of accesses to .data16 variables. When using KEEP_IT_REAL,
* there is no extra cost.
*
* You should place variables in .data16 when they need to be accessed
* by real-mode code. Real-mode assembly (e.g. as created by
* REAL_CODE()) can access these variables via the usual data segment.
* You can therefore write something like
*
* static uint16_t __data16 ( foo );
* #define foo __use_data16 ( foo )
*
* int bar ( void ) {
* __asm__ __volatile__ ( REAL_CODE ( "int $0xff\n\t"
* "movw %ax, foo" )
* : : );
* return foo;
* }
*
* Variables may also be placed in .text16 using __text16 and
* __use_text16. Some variables (e.g. chained interrupt vectors) fit
* most naturally in .text16; most should be in .data16.
*
* If you have only a pointer to a magic symbol within .data16 or
* .text16, rather than the symbol itself, you can attempt to extract
* the underlying symbol name using __from_data16() or
* __from_text16(). This is not for the faint-hearted; check the
* assembler output to make sure that it's doing the right thing.
*/
/**
* Convert segment:offset address to user buffer
*
* @v segment Real-mode segment
* @v offset Real-mode offset
* @ret buffer User buffer
*/
static inline __always_inline userptr_t
real_to_user ( unsigned int segment, unsigned int offset ) {
return ( phys_to_user ( ( segment << 4 ) + offset ) );
}
/**
* Copy data to base memory
*
* @v dest_seg Destination segment
* @v dest_off Destination offset
* @v src Source
* @v len Length
*/
static inline __always_inline void
copy_to_real ( unsigned int dest_seg, unsigned int dest_off,
void *src, size_t n ) {
copy_to_user ( real_to_user ( dest_seg, dest_off ), 0, src, n );
}
/**
* Copy data to base memory
*
* @v dest Destination
* @v src_seg Source segment
* @v src_off Source offset
* @v len Length
*/
static inline __always_inline void
copy_from_real ( void *dest, unsigned int src_seg,
unsigned int src_off, size_t n ) {
copy_from_user ( dest, real_to_user ( src_seg, src_off ), 0, n );
}
/**
* Write a single variable to base memory
*
* @v var Variable to write
* @v dest_seg Destination segment
* @v dest_off Destination offset
*/
#define put_real( var, dest_seg, dest_off ) \
copy_to_real ( (dest_seg), (dest_off), &(var), sizeof (var) )
/**
* Read a single variable from base memory
*
* @v var Variable to read
* @v src_seg Source segment
* @v src_off Source offset
*/
#define get_real( var, src_seg, src_off ) \
copy_from_real ( &(var), (src_seg), (src_off), sizeof (var) )
/*
* REAL_CODE ( asm_code_str )
*
* This can be used in inline assembly to create a fragment of code
* that will execute in real mode. For example: to write a character
* to the BIOS console using INT 10, you would do something like:
*
* __asm__ __volatile__ ( REAL_CODE ( "int $0x16" )
* : "=a" ( character ) : "a" ( 0x0000 ) );
*
*/
#endif /* REALMODE_H */
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