Viewport calculation.

viewport

#include <stdio.h>
#include <stdint.h>
#include <assert.h>

typedef union {
	uint64_t ll;
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
	struct {
		uint32_t lo;
		uint32_t hi;
	};
#else
	struct {
		uint32_t hi;
		uint32_t lo;
	};
#endif
} u_t;

// From include/qemu/bitops.h
static inline uint64_t deposit64(uint64_t value, int start, int length,
				 uint64_t fieldval)
{
	uint64_t mask;
	assert(start >= 0 && length > 0 && length <= 64 - start);
	mask = (~0ULL >> (64 - length)) << start;
	return (value & ~mask) | ((fieldval << start) & mask);
}

static inline uint64_t extract64(uint64_t value, int start, int length)
{
	assert(start >= 0 && length > 0 && length <= 64 - start);
	return (value >> start) & (~0ULL >> (64 - length));
}

void original(uint64_t base, uint32_t limit, uint64_t truelimit)
{
	uint64_t tlimit;
	uint64_t size;

	printf("Original\n");

	size = (uint64_t)limit - base + 1;
	tlimit = base + size - 1;

	printf("Base 0x%lx inferd limit 0x%lx size 0x%lx %s\n",
		base, tlimit, size,
		tlimit == truelimit ? "Good" : "Bad"); 
}

void truncated(uint64_t base, uint32_t limit, uint64_t truelimit)
{
	uint32_t tbase;
	uint32_t tsize;
	uint64_t size;
	uint64_t tlimit;

	printf("Trucated\n");

	// Use 32 bit calculation
	tbase = base; // Truncate
	tsize = limit - tbase;
	// Return to 64 bit
	size = tsize;
	size++;
	tlimit = base + size - 1;

	printf("Base 0x%lx inferd limit 0x%lx size 0x%lx %s\n",
		base, tlimit, size,
		tlimit == truelimit ? "Good" : "Bad"); 
}

void peters(uint64_t base, uint32_t limit, uint64_t truelimit)
{
	uint64_t size;
	uint64_t tlimit;

	printf("Peter's\n");

	tlimit = deposit64(limit, 32, 32, extract64(base, 32, 32));
	size = tlimit - base + 1;
	tlimit = base + size - 1;

	printf("Base 0x%lx inferd limit 0x%lx size 0x%lx %s\n",
		base, tlimit, size,
		tlimit == truelimit ? "Good" : "Bad"); 
}

void my_patch(uint64_t base, uint32_t limit, uint64_t truelimit)
{
	uint64_t tbase;
	uint64_t tlimit;
	uint64_t size;

	printf("My patch\n");

	tbase = base & 0xffffffff;
	tlimit = 0x100000000 + (uint64_t)limit;
	size = ((tlimit - tbase) & 0xffffffff) + 1;

	tlimit = base + size - 1;

	printf("Base 0x%lx inferd limit 0x%lx size 0x%lx %s\n",
		base, tlimit, size,
		tlimit == truelimit ? "Good" : "Bad"); 
}

void do_math(uint64_t base, uint32_t limit, uint64_t truelimit)
{
	uint64_t tlimit;
	uint64_t size;
	uint32_t tsize;
	uint32_t tbase;

	original(base, limit, truelimit);

	printf("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");

	truncated(base, limit, truelimit);

	printf("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");

	peters(base, limit, truelimit);

	printf("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");

	my_patch(base, limit, truelimit);
}

void nxp_example_init(u_t *base, u_t *limit)
{
	base->lo = 0xd0000000;
	base->hi = 0x80000000;
	limit->lo = 0xd000ffff;
	limit->hi = 0x80000000;
}

void peter_example_init(u_t *base, u_t *limit)
{
	base->lo = 0xd0000000;
	base->hi = 0x80000000;
	limit->lo = 0xffffffff;
	limit->hi = 0x80000000;
}

int main(int arc, char *argv[])
{
	u_t base;
	u_t limit;

	printf("=======================================================\n");

	nxp_example_init(&base, &limit);

	printf("-> NXP example: Base 0x%lx Limit 0x%lx\n", base.ll, limit.ll); 
	do_math(base.ll, limit.lo, limit.ll);

	printf("-------------------------------------------------------\n");

	nxp_example_init(&base, &limit);

	base.ll += 0x200000000;
	limit.ll += 0x200000000;


	printf("-> NXP example shifted by 0x200000000 Base 0x%lx Limit 0x%lx\n", base.ll, limit.ll); 
	do_math(base.ll, limit.lo, limit.ll);

	printf("-------------------------------------------------------\n");

	nxp_example_init(&base, &limit);

	base.ll += 0x2ffff000;
	limit.ll += 0x2ffff000;

	printf("-> NXP example shifted by 0x2ffff000 Base 0x%lx Limit 0x%lx\n", base.ll, limit.ll); 
	do_math(base.ll, limit.lo, limit.ll);

	printf("=======================================================\n");

	peter_example_init(&base, &limit);

	printf("Peter's: Base 0x%lx Limit 0x%lx\n", base.ll, limit.ll); 
	do_math(base.ll, limit.lo, limit.ll);

	printf("-------------------------------------------------------\n");

	peter_example_init(&base, &limit);

	base.ll += 0x200000000;
	limit.ll += 0x200000000;

	printf("-> Peter's shifted by 0x200000000 Base 0x%lx Limit 0x%lx\n", base.ll, limit.ll); 
	do_math(base.ll, limit.lo, limit.ll);

	printf("-------------------------------------------------------\n");

	peter_example_init(&base, &limit);

	base.ll += 0x2ffff000;
	limit.ll += 0x2ffff000;

	printf("-> Peter's shifted by 0x2ffff000 Base 0x%lx Limit 0x%lx\n", base.ll, limit.ll); 
	do_math(base.ll, limit.lo, limit.ll);

	printf("=======================================================\n");

	return 0;
}