Re: [PATCH v2 2/3] remoteproc: imx_rproc: Pass bootaddr to SM CPU/LMM reset vector

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Thu, Apr 09, 2026 at 08:30:54AM +0800, Peng Fan wrote:
> On Wed, Apr 08, 2026 at 09:46:32AM -0600, Mathieu Poirier wrote:
> >On Wed, Apr 08, 2026 at 01:30:16AM +0000, Peng Fan wrote:
> >> > Subject: Re: [PATCH v2 2/3] remoteproc: imx_rproc: Pass bootaddr to
> >> > SM CPU/LMM reset vector
> >> > 
> >> [...]
> >> > 
> >> > >
> >> > > Aligning the ELF entry point with the hardware reset base on
> >> > Cortex‑M
> >> > > systems is possible, but it comes with several risks.
> >> > 
> >> > I'm not asking to align the ELF entry point with the hardware reset base.
> >> > All I want is to have the correct start address embedded in the ELF file
> >> > to avoid having to use a mask.
> >> 
> >> I see, per my understanding:
> >> FreeRTOS typically exposes __isr_vector, which corresponds to the hardware
> >> reset / vector table base.
> >> Zephyr (Cortex‑M) exposes _vector_table, which serves the same purpose.
> >> I am not certain about other RTOSes, but the pattern seems consistent:
> >> the vector table base is already available as a named ELF symbol.
> >> 
> >> Given that, if the preferred approach is to parse the ELF and explicitly
> >> retrieve the hardware reset base, I can update the implementation accordingly.
> >> If you prefer to parse the elf file to get the hardware reset base,
> >> I could update to use them.
> >> 
> >> Options1: Something as below:
> >> 1. Include rproc_elf_find_symbol in remoteproc_elf_loader.c
> >> 2. Use below in imx_rproc.c
> >> ret = rproc_elf_find_symbol(rproc, fw, "__isr_vector", &vector_base);
> >> if (ret)
> >>     ret = rproc_elf_find_symbol(rproc, fw, "__vector_table", &vector_base);
> >> 
> >> if (!ret)
> >>     rproc->bootaddr = vector_base
> >> else
> >>    dev_info(dev, "no __isr_vector or __vector_table\n")
> >
> >No
> 
> If your concern is about rproc->bootaddr, I could introduce
> imx_rproc->vector_base for i.MX.  Please help detail a bit.
> 
> >
> >> 
> >> This makes the hardware reset base explicit, avoids masking e_entry.
> >> 
> >> Option 2: User‑provided reset symbol via sysfs 
> >> As an alternative, we could expose a sysfs attribute,
> >> e.g. reset_symbol, allowing users to specify the symbol name
> >> to be used as the reset base:
> >> 
> >> echo __isr_vector > /sys/class/remoteproc/remoteprocX/reset_symbol
> >> 
> >
> >Definitely not.
> >
> >The definition of e_entry in the specification is clear, i.e "the address of the
> >entry point from where the process starts executing".  If masking is required
> >because the tool that puts the image together gets the wrong address, then it
> >should be fixed.
> 
> The hardware reset base is the address from which the hardware fetches the
> initial stack pointer and program counter values and loads them into the SP
> and PC registers.  In contrast, bootaddr (i.e. e_entry) represents the address
> at which the CPU starts executing code (the PC value after reset). As you
> pointed out earlier, this distinction is clear.
> 
> In our case, we need to obtain the hardware reset base and pass that value to
> the system firmware. However, e_entry should not be set to the hardware reset
> base. Doing so would introduce the issues I described in [1]. This means we
> should not modify the Zephyr or FreeRTOS build outputs to make e_entry equal
> to the hardware reset base.


As I said earlier, I am _not_ suggesting to make e_entry equal to the hardware
reset base.

We are going in circles here.

> 
> Given these constraints, the feasible solutions I can see are either:
> - option 1 (explicitly retrieving the hardware reset base), or
> - continuing to use masking.
> 
> Please suggest.
> 
> [1] https://lore.kernel.org/all/acs2PAZq2k3zjmDW@shlinux89/
> 
> Thanks,
> Peng
> 
> >
> >> The remoteproc core would then resolve that symbol from
> >> the ELF and set rproc->bootaddr accordingly.
> >> This provides maximum flexibility but does introduce a new user‑visible ABI,
> >> so I see it more as an opt‑in or fallback mechanism.
> >> 
> >> Please let me know which approach you prefer, and I will update
> >> this series accordingly in v3..
> >> 
> >> Thanks,
> >> Peng.
> >> 
> >> 
> >> > 
> >> > > 1, Semantic mismatch (ELF vs. hardware behavior) 2, Debuggers may
> >> > > attempt to set breakpoints or start execution at the entry symbol
> >> > >