Simple ppc64/ppc64le generated machine code example

jitlab1.c

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <linux/memfd.h>

uint32_t* jitcode;
uint32_t* jitcode_x;
int (*calljit)();

// op comes right out of the PowerISA 3.0 documentation
#define IMM(op, regsd, rega, imm)            (uint32_t)(((op)<<26)|((regsd)<<21)|((rega)<<16)|             (((uint64_t)(imm))&0xFFFF))

int main(int argc, char** argv) {
	int fd, rv = 0;
	size_t pagesize;

	pagesize = sysconf(_SC_PAGE_SIZE);
/*
	if (posix_memalign((void **)&jitcode, pagesize, rv) != 0) {
		perror("posix_memalign");
		return -1;
	}
	if (mprotect(jitcode, pagesize, PROT_READ|PROT_WRITE|PROT_EXEC)) {
		perror("mprotect");
		return -1;
	}
*/
/*
	fd = memfd_create("jitlab", MFD_CLOEXEC);
*/
	fd = syscall(__NR_memfd_create, "jitlab", MFD_CLOEXEC);
	ftruncate(fd, pagesize);
	jitcode = (uint32_t*)mmap(NULL, pagesize,
		PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

	jitcode[0] = IMM(14, 3,  0, 2020);   // li r3, 2020
	jitcode[1] = IMM(19, 20, 0,   32);   // blr

	fprintf(stdout, "jitcode at 0x%llx\n", (uint64_t)jitcode);
	asm volatile(
		"dcbst %y0\n"
		"sync\n"
		"icbi %y0\n"
		"isync\n"
	:: "Z"(*jitcode));

	jitcode_x = (uint32_t*)mmap(NULL, pagesize,
		PROT_READ|PROT_EXEC, MAP_SHARED, fd, 0);
	calljit = (int (*)())jitcode_x;
	rv = calljit();

	fprintf(stdout, "result = %d\n", rv);
	munmap(jitcode, pagesize);
	munmap(jitcode_x, pagesize);
	close(fd);
	return 0;
}