topic Re: Is it possible to set a hardware breakpoint on a memory write in Linux on the i.MX6ULL? in i.MX Processors

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

JohnKlug — Thu, 13 Mar 2025 21:18:41 GMT

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

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

JosephAtNXP — Thu, 13 Mar 2025 22:50:38 GMT

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

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

JohnKlug — Fri, 14 Mar 2025 00:37:15 GMT

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

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

JohnKlug — Fri, 14 Mar 2025 14:26:51 GMT

Maybe this code is obsolete that you sent?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?

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

JohnKlug — Mon, 24 Mar 2025 22:01:47 GMT

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.