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Annotation of Gnu-Mach/i386/pc/i16/i16_raw_test_a20.S, revision 1.1.1.1

1.1       root        1: 
                      2: #include <mach/machine/asm.h>
                      3: 
                      4:        .text
                      5:        .code16
                      6: 
                      7: /*
                      8:  * Test the A20 address line; return true if it is enabled.
                      9:  */
                     10: ENTRY(i16_raw_test_a20)
                     11:        xorw    %ax,%ax
                     12:        movw    %ax,%fs
                     13:        notw    %ax
                     14:        movw    %ax,%gs
                     15: 
                     16:        /* See if the values in already in the corresponding locations
                     17:           are the same.  */
                     18:        movw    %fs:0,%ax
                     19:        cmpw    %gs:16,%ax
                     20:        jnz     1f
                     21: 
                     22:        /* Yes; try changing one and see if they're still the same.  */
                     23:        movw    %ax,%dx
                     24:        notw    %ax
                     25:        movw    %ax,%fs:0
                     26:        cmpw    %gs:16,%ax
                     27:        movw    %dx,%fs:0
                     28:        jnz     1f
                     29: 
                     30:        xorl    %eax,%eax
                     31:        ret
                     32: 1:
                     33:        movl    $1,%eax
                     34:        ret
                     35: 

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