67 lines
1.2 KiB
ArmAsm
67 lines
1.2 KiB
ArmAsm
/*
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gint_vbr
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Some of the work, especially related to setting and un-setting the vbr
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address needs to be done in assembler.
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*/
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.global _gint_getVBR
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.global _gint_setVBR
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/*
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gint_getVBR()
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Returns the current vbr address.
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*/
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_gint_getVBR:
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rts
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stc vbr, r0
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/*
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gint_setVBR()
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This is quite the hard part when modifying the vbr. We need to set
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immediately the interrupt priorities of our own handler, or restore
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the ones used by the system ; otherwise we may receive interrupts
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requests that the new handler doesn't handle, which will cause the
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whole program to freeze.
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Therefore, we must set vbr *and* change interrupt priorities while
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having disabled all the interrupts in the status register. That's why
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this function takes as parameter the priority management function.
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*/
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_gint_setVBR:
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sts.l pr, @-r15
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/* Blocking all interrupts. */
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mov.l sr_block, r0
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stc sr, r3
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or r0, r3
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ldc r3, sr
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/* Setting the vbr address. */
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ldc r4, vbr
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/* Calling the priority manager. */
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jsr @r5
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nop
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/* Activating interrupts again. */
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mov.l sr_block, r0
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not r0, r0
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stc sr, r3
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and r0, r3
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ldc r3, sr
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lds.l @r15+, pr
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rts
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nop
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.align 4
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sr_block:
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.long (1 << 28)
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