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The original BBL boot method had the kernel embedded as an opaque blob that was blindly jumped to, which OpenSBI implemented as fw_payload. OpenSBI then implemented fw_jump, which allows the payload to be loaded elsewhere, but still blindly jumps to a fixed address at which the kernel is to be loaded. Finally, OpenSBI introduced fw_dynamic, which allows the previous stage to inform it where to jump to, rather than having to blindly guess like fw_jump, or embed the payload as part of the build like fw_payload. When used with an opaque binary (i.e. the output of objcopy -O binary), it matches the behaviour of the previous methods. However, when used with an ELF, QEMU currently passes on the ELF's entry point address, which causes a discrepancy compared with all the other boot methods if that entry point is not the first instruction in the binary. This difference specific to fw_dynamic with an ELF is not apparent when booting Linux, since its entry point is the first instruction in the binary. However, FreeBSD has a separate ELF entry point, following the calling convention used by its bootloader, that differs from the first instruction in the binary, used for the legacy SBI entry point, and so the specific combination of QEMU's default fw_dynamic firmware with booting FreeBSD as an ELF rather than a raw binary does not work. Thus, align the behaviour when loading an ELF with the behaviour when loading a raw binary; namely, use the base address of the loaded kernel in place of the entry point. The uImage code is left as-is in using the U-Boot header's entry point, since the calling convention for that entry point is the same as the SBI one and it mirrors what U-Boot will do. Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com> Reviewed-by: Alistair Francis <alistair.francis@wdc.com> Message-Id: <20211214032456.70203-1-jrtc27@jrtc27.com> Signed-off-by: Alistair Francis <alistair.francis@wdc.com> |
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.. | ||
boot.c | ||
Kconfig | ||
meson.build | ||
microchip_pfsoc.c | ||
numa.c | ||
opentitan.c | ||
riscv_hart.c | ||
shakti_c.c | ||
sifive_e.c | ||
sifive_u.c | ||
spike.c | ||
virt.c |