probe-run assumes stack fits within a memory region

[thejpster]

Describe the bug

The memory map for the RP2040 in probe-rs describes a 256 KiB block at 0x2000_0000 (SRAM_REGION_0 .. SRAM_REGION_3, striped) and then two 4 KiB blocks at 0x2004_0000 (SRAM_REGION_4) and 0x2004_1000 (SRAM_REGION_5).

probe-rs finds the reset stack pointer, and then assumes that the stack must lie within a single memory region.

I have written an application where the top of stack is at 0x2004_1000 and I have 8 KiB of space allocated - 4 KiB from a SRAM_REGION_4 and then 4 KiB from the top of the striped region. The regions are consecutive, so this works fine.

However, probe-run tells me I only have 4096 bytes of stack (not 8192 bytes) and thus tells me I have used all of my stack, when I have not.

To Reproduce
Steps to reproduce the behavior:

memory.x:

MEMORY {
    /*
     * This is bootloader for the RP2040. It must live at the start of the
       external flash chip.
     */
    BOOT2 : ORIGIN = 0x10000000, LENGTH = 0x100
    /*
     * The Pico has 2048 KiB of external Flash Memory. We allow ourselves 128
     * KiB for the BIOS, leaving the rest
     * for the OS and any user applications.
     */
    FLASH : ORIGIN = 0x10000100, LENGTH = 128K - 0x100
    /*
     * This is the remainder of the 2048 KiB flash chip.
     */
    FLASH_OS : ORIGIN = 0x10020000, LENGTH = 2048K - 128K
    /*
     * This is the bottom of the four striped banks of SRAM in the RP2040.
     */
    RAM_OS : ORIGIN = 0x20000000, LENGTH = 0x39000
    /*
     * This is the top of the four striped banks of SRAM in the RP2040.
     *
     * We give ourselves size 4K pages [0x39_000..0x3E_FFF]
     */
    RAM : ORIGIN = 0x20039000, LENGTH = 24K
    /*
     * This 4K from the top of striped RAM, plus the fifth bank - another a 4KB
     * block. We use this for Core 0 Stack. We tried 4K but it wasn't enough.
     */
    RAM_CORE0_STACK : ORIGIN = 0x2003F000, LENGTH = 8K
    /*
     * This is the sixth bank, a 4KB block. We use this for Core 1 Stack.
     * As of 0.5.1 Pico BIOS uses about 316 bytes of this but we give it the
     * full 4K so it can have uncontended access to this SRAM bank.
     */
    RAM_CORE1_STACK : ORIGIN = 0x20041000, LENGTH = 4K
}

/*
 * This is where the call stack for Core 0 will be located. The stack is of
 * the full descending type. You may want to use this variable to locate the
 * call stack and static variables in different memory regions.
 */
_stack_start = ORIGIN(RAM_CORE0_STACK) + LENGTH(RAM_CORE0_STACK);
_stack_bottom = ORIGIN(RAM_CORE0_STACK);
_stack_len = LENGTH(RAM_CORE0_STACK);

Expected and observed behavior

probe-run could:

• Realise that memory regions may be contiguous and a stack may spread across them
• Use the symbol table to find where each value in memory lives.
• Start at the stack top and work downwards until it hits a discontinuity in the memory regions, or it hits memory allocated for a variable.

config.toml
The contents of your project's .cargo/config.toml file

[target.thumbv6m-none-eabi]
# This will make a UF2 and copy it to the RP2040's Mass Storage Device bootloader
# runner = "elf2uf2-rs -d"
# This will flash over SWD with any compatible probe it finds. You need 0.3.1 or higher for RP2040 support.
runner = "probe-run --chip RP2040 --measure-stack"
rustflags = [
  # This is needed if your flash or ram addresses are not aligned to 0x10000 in memory.x
  # See https://github.com/rust-embedded/cortex-m-quickstart/pull/95
  "-C",
  "link-arg=--nmagic",
  # LLD (shipped with the Rust toolchain) is used as the default linker
  "-C",
  "link-arg=-Tlink.x",
  # Support defmt formatted logging
  "-C",
  "link-arg=-Tdefmt.x",
]

[build]
target = "thumbv6m-none-eabi" # Cortex-M0 and Cortex-M0+

Probe details

$ probe-run --list-probes
the following probes were found:
[0]: Debug Probe (CMSIS-DAP) (VID: 2e8a, PID: 000c, Serial: E6614103E7104D2F, CmsisDap)```
$ probe-run --version
0.3.9 
supported defmt versions: 3, 4

Operating System:

Linux