49 lines
2 KiB
C
49 lines
2 KiB
C
// randProbe.c -- verify that crt0's __srandInitFromTime hook ran.
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//
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// With the old (pre-Phase 1.8) crt0 the seed was a constant 1, so the
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// first rand() output was deterministically:
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// (1*1103515245 + 12345) = 0x41C64E4D
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// (>> 16) & 0x7FFF = 0x41C6 & 0x7FFF = 0x41C6 (16838)
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// If __srandInitFromTime ran, rand() now starts from a time-derived
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// seed and the first output is overwhelmingly unlikely to be 0x41C6.
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//
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// We probe via bank-0 single-byte writes ($70..$73) because the
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// runViaFinder harness reads u8 and the const-int byte-store path in
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// our codegen (STA8long) MASKS the address to 16 bits by design
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// (W65816AsmPrinter.cpp:780-782 -- "users who need a banked address
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// should construct a far pointer rather than casting an int"). Using
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// addresses in zero-page / first-page bank-0 sidesteps that limitation
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// and keeps the probe self-contained.
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//
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// $70 (u8) : low byte of rand() #1
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// $71 (u8) : high byte of rand() #1
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// $72 (u8) : non-zero IF rand1 != the deterministic 0x41C6.
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// 0x99 = seeded ok, 0x00 = still seed=1 default = test failed.
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// $73 (u8) : marker 0x99 -- proves the program executed at all.
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//
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// Build + run (GS/OS Finder path):
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// bash demos/build.sh randProbe
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// bash scripts/runViaFinder.sh demos/randProbe.omf \
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// --check 0x72=0x99 0x73=0x99
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// Build + run (GNO command path):
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// bash demos/buildGno.sh randProbe
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// bash scripts/runInGno.sh demos/randProbe.omf --check 0x72=9999
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#include <stdint.h>
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#include <stdlib.h>
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#include "iigs/toolbox.h"
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extern void iigsToolboxInit(void);
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int main(void) {
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iigsToolboxInit(); // TL up under GS/OS already; explicit init keeps
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// the demo bare-metal-runnable too.
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uint16_t r1 = (uint16_t)rand();
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*(volatile uint8_t *)0x70 = (uint8_t)(r1 & 0xFFu);
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*(volatile uint8_t *)0x71 = (uint8_t)((r1 >> 8) & 0xFFu);
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*(volatile uint8_t *)0x72 = (r1 == 0x41C6u) ? 0x00u : 0x99u;
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*(volatile uint8_t *)0x73 = 0x99u;
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for (volatile unsigned long i = 0; i < 300000UL; i++) {}
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return 0;
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}
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