wolfBoot PolarFire SoC M-mode target with the Yocto RISC-V toolchain and ECC384 FIT signing

[dgarske]

Builds wolfBoot's standalone M-mode PolarFire SoC target (polarfire_mpfs250_m.config, which replaces the Hart Software Services (HSS)) with the BSP's riscv64 Linux toolchain, and signs the Microchip BSP FIT for it.

What it adds

• wolfboot.inc - WOLFBOOT_GIT_URI / WOLFBOOT_GIT_BRANCH, so a fork or pre-merge branch can be selected from local.conf
• wolfboot-signed-image.bb - WOLFBOOT_SIGN_ALGO / WOLFBOOT_HASH_ALGO (defaults unchanged: rsa4096 / sha3), and a version-independent image_signed.bin link in the deploy directory for wic layouts
• wic/mpfs-wolfboot.wks - the BSP SD layout with the signed FIT raw in partition 1, where wolfBoot's disk loader reads it
• README section for the PolarFire quick start (Libero config directory, ECC384 key pair, gzip FIT)

Changes to wolfboot_git.bb

• Toolchain flags for the bootloader go into .config as CFLAGS_EXTRA / LDFLAGS_EXTRA instead of CC / LD on the make command line, which leaked the cross compiler into the sub-makes that build wolfBoot's host-side tools. A wolfBoot tree without the LDFLAGS_EXTRA consumer still gets the link flags through the LD override, so existing pins keep building.
• -fno-pie / -no-pie / -Wl,--build-id=none: a default-PIE Linux toolchain otherwise produces a PIE and places a build-id note at the image base, ahead of the boot vector.
• WOLFBOOT_NOSTDLIB for targets whose ABI the sysroot's libgcc does not match (M-mode is soft-float lp64 on an lp64d toolchain), plus empty gnu/stubs-<abi>.h for the ABI names glibc's stubs.h would otherwise fail to find.
• Objects are cleared before make, so a re-run of do_compile with changed flags does not reuse objects from the previous configuration.

Needs the wolfBoot side of this change (LDFLAGS_EXTRA consumer, prebuilt KEYGEN_TOOL / SIGN_TOOL, libgcc-free FDT byte swaps): wolfSSL/wolfBoot#921.

Hardware / test status

PolarFire SoC Video Kit (MPFS250TS), meta-mchp linux4microchip+fpga-2025.10 (Scarthgap): wolfboot.elf programmed to eNVM with mpfsBootmodeProgrammer, the wic written to the SD card; wolfBoot verifies the ECC384-signed FIT and boots Linux 6.12 to the login prompt. The existing ZynqMP flow was not re-tested on hardware.

Scope

The Libero fpga_design_config directory and the signing key pair stay user-supplied paths. HSS payload generation for the S-mode (HSS-hosted) wolfBoot configuration is not covered.

[Copilot]

Copilot review overview

🟡 Changes recommended

The default wolfBoot revision lacks required linker support, and the Wic partition mapping conflicts with wolfBoot’s configured A/B slots.

Review effort: Balanced
Findings: 2

Open (2)

• Pin wolfBoot revision supporting LDFLAGS_EXTRA · New
• Correct GPT slot mapping for A/B failover · New

What changed in this PR

Adds PolarFire SoC M-mode wolfBoot builds and ECC384-signed FIT image generation using Yocto’s RISC-V toolchain.

Changes:

• Adds configurable wolfBoot sources and signing algorithms.
• Adds PolarFire-specific toolchain handling and documentation.
• Adds a PolarFire SD-card Wic layout.

File	Description
wic/​mpfs-wolfboot.wks	Defines the PolarFire SD-card layout.
recipes-wolfssl/​wolfboot/​wolfboot.inc	Makes wolfBoot repository and branch configurable.
recipes-wolfssl/​wolfboot/​wolfboot-signed-image.bb	Supports configurable signing and stable artifact naming.
recipes-wolfssl/​wolfboot/​wolfboot_git.bb	Adds RISC-V toolchain flags and native key-tool handling.
recipes-wolfssl/​wolfboot/​README.md	Documents the PolarFire build and deployment flow.

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