[PATCH] docs: platform: update qemu_virt.md

[Anup Patel]

On Thu, Mar 19, 2026 at 6:28 PM <runmin.zhang at ingenic.com> wrote:
>
> From: Zhang RunMin <runmin.zhang at ingenic.com>
>
> When using GDB for debugging, if FW_TEXT_START is not set to 0x80000000
> during compilation, the following error occurs:
>
> Reading symbols from build/platform/generic/firmware/fw_payload.elf...
> Remote debugging using localhost:1234
> mips_warm_boot ()
>     at /home/zrmin/opensbi/platform/generic/mips/mips_warm_boot.S:11
> 11      j       _start_warm
> (gdb) b _start
> Breakpoint 1 at 0x0: file /home/zrmin/opensbi/firmware/fw_base.S, line 50.
> (gdb) c
> Continuing.
> Remote connection closed
> (gdb)
>
> With FW_TEXT_START=0x80000000, debugging works correctly:
> Reading symbols from build/platform/generic/firmware/fw_payload.elf...
> Remote debugging using localhost:1234
> 0x0000000000001000 in ?? ()
> (gdb) b _start
> Breakpoint 1 at 0x80000000: file /home/zrmin/opensbi/firmware/fw_base.S, line 50.
> (gdb) c
> Continuing.
>
> Breakpoint 1, _start () at /home/zrmin/opensbi/firmware/fw_base.S:50
> 50      MOV_3R  s0, a0, s1, a1, s2, a2
> (gdb)
>
> This is because QEMU loads OpenSBI at address 0x80000000. When
> FW_TEXT_START does not match this address, the debug symbols are
> incorrectly offset, causing GDB to fail to set breakpoints properly.
>
> Signed-off-by: Zhang RunMin <runmin.zhang at ingenic.com>

LGTM.

Reviewed-by: Anup Patel <anup at brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup

> ---
>  docs/platform/qemu_virt.md | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/docs/platform/qemu_virt.md b/docs/platform/qemu_virt.md
> index fd87ee5a..4513df8b 100644
> --- a/docs/platform/qemu_virt.md
> +++ b/docs/platform/qemu_virt.md
> @@ -158,6 +158,9 @@ qemu-system-riscv32 -M virt -m 256M -nographic \
>  Debugging with GDB
>  ------------------
>
> +Note: the command line examples here assume that OpenSBI was compiled using
> +the `DEBUG=1 FW_TEXT_START=0x80000000` configuration.
> +
>  In a first console start OpenSBI with QEMU:
>
>  ```
> --
> 2.43.0
>
>
> --
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