Fix: unexpected E02 from gdb m-packets #2041

ALTracer commented 2025年01月06日 04:18:05 +01:00 (Migrated from github.com)

Detailed description

• This is a minor but important bugfix.
• The existing problem is gdbserver returning unexpected read errors E02 Cannot access memory at address to otherwise normal accesses.
• The PR solves it by fixing a mistranslated bounds-check introduced in ca. v1.10.0-1567-g de645593 of #2014.

Tested on gd32f103cb bluepillplus running bluepill.ini/stlink BMF; and BMDA; against stm32g474ce. At first I expected wrong RCC/Flash config or invalid SRAM mapping, but interactive debugging of BMDA and extended logging proved otherwise.
Note: (gdb) maintenance packet m08070000,201 triggers a 513 byte read which is rejected by BMD. Only <=512 is good because of 1024 byte RSP packet buffer.

Your checklist for this pull request

• I've read the Code of Conduct
• I've read the guidelines for contributing to this repository
• It builds for hardware native (see Building the firmware)
• It builds as BMDA (see Building the BMDA)
• I've tested it to the best of my ability
• My commit messages provide a useful short description of what the commits do

Closing issues

## Detailed description * This is a minor but important bugfix. * The existing problem is gdbserver returning unexpected read errors E02 `Cannot access memory at address` to otherwise normal accesses. * The PR solves it by fixing a mistranslated bounds-check introduced in ca. v1.10.0-1567-g de645593 of #2014. Tested on gd32f103cb bluepillplus running bluepill.ini/stlink BMF; and BMDA; against stm32g474ce. At first I expected wrong RCC/Flash config or invalid SRAM mapping, but interactive debugging of BMDA and extended logging proved otherwise. Note: `(gdb) maintenance packet m08070000,201` triggers a 513 byte read which is rejected by BMD. Only <=512 is good because of 1024 byte RSP packet buffer. ## Your checklist for this pull request * [x] I've read the [Code of Conduct](https://github.com/blackmagic-debug/blackmagic/blob/main/CODE_OF_CONDUCT.md) * [x] I've read the [guidelines for contributing](https://github.com/blackmagic-debug/blackmagic/blob/main/CONTRIBUTING.md) to this repository * [x] It builds for hardware native (see [Building the firmware](https://github.com/blackmagic-debug/blackmagic?tab=readme-ov-file#building-black-magic-debug-firmware)) * [x] It builds as BMDA (see [Building the BMDA](https://github.com/blackmagic-debug/blackmagic?tab=readme-ov-file#building-black-magic-debug-app)) * [x] I've tested it to the best of my ability * [x] My commit messages provide a useful short description of what the commits do ## Closing issues

perigoso commented 2025年01月06日 13:00:08 +01:00 (Migrated from github.com)

Thanks for the cleanup, good catch!

I see this uses alloca a couple lines down, and I do see a way we can optimize that out!

Thanks for the cleanup, good catch! I see this uses alloca a couple lines down, and I do see a way we can optimize that out!