Alexandre IOOSS <erdn...@crans.org> writes:
> [[PGP Signed Part:Undecided]] > On 6/22/21 12:37 PM, Alex Bennée wrote: >> Alexandre IOOSS <erdn...@crans.org> writes: >> >>> [[PGP Signed Part:Undecided]] >>> On 6/22/21 10:48 AM, Alex Bennée wrote: >>>> Alexandre Iooss<erdn...@crans.org> writes: >>>>> [...] >>>>> + >>>>> +The execlog tool traces executed instructions with memory access. It can >>>>> be used >>>>> +for debugging and security analysis purposes. >>>> We should probably mention that this will generate a lot of output. >>>> Running the admittedly memory heavy softmmu memory test: >>>> ./aarch64-softmmu/qemu-system-aarch64 -D test.out -d plugin \ >>>> -plugin contrib/plugins/libexeclog.so \ >>>> -cpu max -serial mon:stdio -M virt \ >>>> -display none -semihosting-config chardev=serial0 \ >>>> -kernel ./tests/tcg/aarch64-softmmu/memory >>>> generates a 8.6Gb text file. I suspect once this is merged you might >>>> want to look at options to target the instrumentation at areas of >>>> specific interest or abbreviate information. >>> >>> Yes! In my downstream version I am triggering the beginning and the >>> end of trace acquisition by matching two virtual addresses of GPIO >>> device access. This works in my case because I'm also using the same >>> GPIO for triggering an oscilloscope, but maybe we would like to >>> upstream something more generic. >>> >>> I'm still thinking about this (maybe for a later patch) but I believe >>> it would be nice to have the following: >>> - If no argument is given to the plugin, log everything. >>> - Allow the user to specify either a memory address, an instruction >>> virtual address or an opcode that would start the acquisition. >>> - Same to stop the acquisition. >> Sounds reasonable to me. >> >>> This would look like this to start/stop acquisition using GPIO PA8 on >>> STM32VLDISCOVERY: >>> >>> ./arm-softmmu/qemu-system-arm -M stm32vldiscovery \ >>> -kernel ./firmware.elf -d plugin \ >>> -plugin libexeclog.so,arg=mem:1073809424,arg=mem:1073809424 >> I quite like the formats you can use for -dfilter, for example: >> 0x1000+0x100,0x2100-0x100,0x3000..0x3100 >> it might even be worth exposing qemu_set_dfilter_ranges as a helper >> function to plugins to avoid copy and paste. > > We could expose "-dfilter", but maybe it is better to reserve it to > filter the output of the plugin rather than triggering the tracing? I meant the parsing code for dfilter style expressions, the dfilter itself ;-) > I could implement a format similar to dfilter to configure triggering. > This would enable someone to start logging on any access to a memory > range. > >> So what would your above command trigger? A write to 1073809424 >> would >> start the trace and the next write to the same address would stop it? >> > > Yes exactly. In this case the first access set the GPIO high, and the > second access set it low. > > I don't believe the plugin can access the value stored in memory (i.e. > differentiating between setting a GPIO output high or low). I don't > find this problematic in my case, but maybe it could be for someone > else. Not currently but in principle it wouldn't be too hard to do. It would just be extra data to copy into a TCG Arg. We would probably want to make it optional though. > > From the discussion I see the following possible patches: > 1. Add an argument to trigger the beginning with one address (memory > or instruction). > 2. Add an argument to trigger the end with one address (memory or > instruction). > 3. Add the support for ranges (in "dfilter" style). > 4. (maybe) Add the support to trigger on an opcode. > 5. Add support for "-dfilter" to filter the logging output. > > Thanks, > -- Alexandre > > [[End of PGP Signed Part]] -- Alex Bennée
