The M7 processor supports an Application Data Integrity (ADI) feature that detects invalid data accesses. When software allocates memory and enables ADI on the allocated memory, it chooses a 4-bit version number, sets the version in the upper 4 bits of the 64-bit pointer to that data, and stores the 4-bit version in every cacheline of that data. Hardware saves the latter in spare bits in the cache and memory hierarchy. On each load and store, the processor compares the upper 4 VA (virtual address) bits to the cacheline's version. If there is a mismatch, the processor generates a version mismatch trap which can be either precise or disrupting. The trap is an error condition which the kernel delivers to the process as a SIGSEGV signal.
Note that only 64-bit applications can use ADI and need to be built with ADI-enabled.
Values of the ADI version tags, which are in granularity of a cacheline (64 bytes), can be viewed or modified.
adi (examine | x) [ / n ] addradi examine command displays the value of one ADI version tag per
cacheline.
n is a decimal integer specifying the number in bytes; the default is 1. It specifies how much ADI version information, at the ratio of 1:ADI block size, to display.
addr is the address in user address space where you want gdb to begin displaying the ADI version tags.
Below is an example of displaying ADI versions of variable "shmaddr".
(gdb) adi x/100 shmaddr
0xfff800010002c000: 0 0
adi (assign | a) [ / n ] addr = tagadi assign command is used to assign new ADI version tag
to an address.
n is a decimal integer specifying the number in bytes; the default is 1. It specifies how much ADI version information, at the ratio of 1:ADI block size, to modify.
addr is the address in user address space where you want gdb to begin modifying the ADI version tags.
tag is the new ADI version tag.
For example, do the following to modify then verify ADI versions of variable "shmaddr":
(gdb) adi a/100 shmaddr = 7
(gdb) adi x/100 shmaddr
0xfff800010002c000: 7 7