tools/power turbostat: Fix PMT mmap size and bounds check

Remove assert(offset == 0), to allow non-zero PMT offsets.

Fix the pmt_mmio_open() mapping to round-up (offset + size).

Fix the offset bounds check to disallow running past the end of the region.

[lenb: commit message re-write]
Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

tools/power/x86/turbostat/turbostat.c

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 0ba51e6..f5a7654 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -10266,13 +10266,11 @@ struct pmt_mmio *pmt_mmio_open(unsigned int target_guid)
 			break;
 		}
 
-		assert(offset == 0);
-
 		fd_pmt = openat(fd_telem_dir, "telem", O_RDONLY);
 		if (fd_pmt == -1)
 			goto loop_cleanup_and_break;
 
-		mmap_size = ROUND_UP_TO_PAGE_SIZE(size);
+		mmap_size = ROUND_UP_TO_PAGE_SIZE(offset + size);
 		mmio = mmap(0, mmap_size, PROT_READ, MAP_SHARED, fd_pmt, 0);
 		if (mmio != MAP_FAILED) {
 			if (debug)
@@ -10444,7 +10442,7 @@ int pmt_add_counter(unsigned int guid, unsigned int seq, const char *name, enum
 		return 1;
 	}
 
-	if (offset >= mmio->size) {
+	if (offset > mmio->size || mmio->size - offset < 8) {
 		if (mode != PMT_OPEN_TRY) {
 			fprintf(stderr, "%s: offset %u outside of PMT MMIO size %u\n", __func__, offset, mmio->size);
 			exit(1);