fix(esp_ulp): Add support for multiple ULP program embedding without name collision (IDFGH-14152)

[X-Ryl669]

Description

Currently, the ULP's auto variable name embedding script has multiple issues:

1. It names variable in the global namespace (in extern "C" mode) so multiple ULP program using the same variable name results in impossible-to-solve access and memory corruption (see linked issue)
2. It doesn't support generating arrays (so one has to trick/hack around a declared variable, rendering the whole process useless)
3. It create a useless linker script in the build process
4. It creates a lots of useless symbols declaration (like all functions and global included objects), which, if used in the HP core, crashes the HP core

This PR fixes it:

1. It changes from using nm cross compilation tool to readelf tool for extracting symbols. This allows keeping the symbol's scope (global or local), the symbol type (object or function or ...) and the symbol size (for arrays).
2. It only extract the meaningful symbols and doesn't pollute the global scope with unusable symbols like ulp_lp_core_lp_ana_peri_intr_handler
3. It allows to specify the prefix to use for generating the ULP's variable name (defaults to the current ulp_ prefix, but now, you can specify it)
4. You can use C++ prefix too (like a namespace ULPmain:: and it'll mangle the name and work without extern "C"): perfect to move the shorter variables in their own namespace and avoid collisions without dumb long names
5. It removes the generated linker script (useless to specify the symbol location, it can be done in the header file directly).
6. It add support for array uint32_t myVariable[32] is correctly exported so can be used like a native variable in HP core, no more hacky ((uint32_t*)myVariable)[0] like specified in the documentation.

From a user perspective, nothing changes (the useless symbol will be removed, but they couldn't be used anyway previously).
However, she can now replace the line:

set(ulp_app_name ulp_${COMPONENT_NAME})
set(ulp_sources "ulp/ulp_main.c")
set(ulp_exp_dep_srcs ${srcs})

ulp_embed_binary(${ulp_app_name} "${ulp_sources}" "${ulp_exp_dep_srcs}")

set(ulp_app_name2 ulp_ds_cal)
set(ulp_sources2 "ulp/ulp_ds_cal.c")

ulp_embed_binary_prefix(${ulp_app_name2} "${ulp_sources2}" "${ulp_exp_dep_srcs}")

to this:

set(ulp_app_name ulp_${COMPONENT_NAME})
set(ulp_sources "ulp/ulp_main.c")
set(ulp_exp_dep_srcs ${srcs})

ulp_embed_binary_prefix(${ulp_app_name} "ULPmain::" "${ulp_sources}" "${ulp_exp_dep_srcs}")

set(ulp_app_name2 ulp_ds_cal)
set(ulp_sources2 "ulp/ulp_ds_cal.c")

ulp_embed_binary_prefix(${ulp_app_name2} "ULPds_cal::" "${ulp_sources2}" "${ulp_exp_dep_srcs}")

And build collision-free and working multiple ULP binary.

Related

Fix #14945 and other issues too related to misusage of ULP symbols in HP core.

Testing

I've tested on my system with ESP32C6. I haven't tested with other CPU types.
However, the tools used in this PR are common cross compilation tools, it shouldn't depend on the CPU architecture.

Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

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[igrr]

Should the file name be .hpp for C++ case, making it clear that the file shall not be usable from C code?

[X-Ryl669]

Can be. It probably make more sense, I'll change that.

[X-Ryl669]

Tried to do that but it's a PITA since changing the extension here means also making the CMake code conditional to the prefix type (make all dependency tracking & artifacts as variable, ...). I don't think it matters anyway, the only way to get a C++ header is to specify a prefix with a namespace declaration, and in that case, if the .h header is included in a C source file, the compiler will just choke on the "namespace" part so it's pretty obvious.

[igrr]

@X-Ryl669 Thank you for the PR. We can definitely accept the changes related to customization the prefix (ulp_). The part related to replacement of the linker script with inline assembly looks more risky for the reason mentioned above.

[X-Ryl669]

I've reworked the PR to fit the review. I've reverted the linker script removal and instead changed its format so if the declared symbols already exists, it errors out with a meaningful error. This should prevent silent building and runtime crash on colliding name for multiple ULP programs. I've also removed the ulp_embed_binary_prefix and instead added a named parameter to the function (called PREFIX). I've fixed the documentation to match the changes and describe the new prefix option.