Is it possible to set a hardware breakpoint on a memory write in Linux on the i.MX6ULL?

[JohnKlug]

		attr.bp_addr = (unsigned long)&mydata;
		attr.bp_len = HW_BREAKPOINT_LEN_4;
		attr.bp_type = HW_BREAKPOINT_W;
		bps = register_wide_hw_breakpoint(&attr, gpio_dump_stack, NULL);
		if(IS_ERR(bps)) {
		    pr_err("Failed to register hardware breakpoint: %ld\n",PTR_ERR(bps));
		    bps = NULL;
NULL);
		}

This prints:
Failed to register hardware breakpoint: -19

-19 is ENODEV.


I have the following flags added to the kernel:
CONFIG_HAVE_HW_BREAKPOINT=y
CONFIG_KPROBES=y

I am using kernel:
https://github.com/nxp-imx/linux-imx.git

With branch lf-5.15.y

[JohnKlug]

Unfortunately the sample fails in symbol_get:



bash# modprobe databrkpt
[ 3868.245139] failing symbol_get of non-GPLONLY symbol jiffies.
modprobe: ERROR: could not insert 'databrkpt': No such device or address

I shortened the driver name to databrkpt.

This error is found in the code here:

Symbol not found error 

[JohnKlug]

Maybe this code is obsolete that you sent?

jiffies probably is no longer a symbol.

Here is a symbol:

bash# modprobe databrkpt ksym=pm_power_off_prepare
[ 1405.440261] Failed to register hardware breakpoint: -19
[ 1405.445552] Breakpoint registration failed
modprobe: ERROR: could not insert 'databrkpt': No such device


pm_poweroff_prepare is found here:


kernel/reboot.c:EXPORT_SYMBOL_GPL(pm_power_off_prepare);

So the question remains, how does one set a hardware breakpoint? Are there kernel configuration parameters that I have not set?

[JosephAtNXP]

Hi,

Thank you for your interest in NXP Semiconductor products,

You can base the usage of HW BP in the next sample.

It should support any transaction of SDMA memory bus and the core.

Regards

[JohnKlug]

We happen to have the Technexion PICO-PI-IMX8M with four cores. The driver you suggests works fine on the i.MX8 CPU on this board. So I will have to move my driver to this platform to debug it.