Re: [PATCH v13 1/2] generic-loader: Add a generic loader

[Alistair Francis]

On Thu, Nov 28, 2024 at 2:09 AM Philippe Mathieu-Daudé
<philmd@linaro.org> wrote:
>
> Hi,
>
> [very old patch merged as commit e481a1f63c93]
>
> On 30/9/16 02:25, Alistair Francis wrote:
> > Add a generic loader to QEMU which can be used to load images or set
> > memory values.
> >
> > Internally inside QEMU this is a device. It is a strange device that
> > provides no hardware interface but allows QEMU to monkey patch memory
> > specified when it is created. To be able to do this it has a reset
> > callback that does the memory operations.
> >
> > This device allows the user to monkey patch memory. To be able to do
> > this it needs a backend to manage the datas, the same as other
> > memory-related devices. In this case as the backend is so trivial we
> > have merged it with the frontend instead of creating and maintaining a
> > seperate backend.
> >
> > Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
> > Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> > Acked-by: Markus Armbruster <armbru@redhat.com>
> > ---
>
> > diff --git a/hw/core/generic-loader.c b/hw/core/generic-loader.c
> > new file mode 100644
> > index 0000000..79ab6df
> > --- /dev/null
> > +++ b/hw/core/generic-loader.c
> > @@ -0,0 +1,211 @@
> > +/*
> > + * Generic Loader
> > + *
> > + * Copyright (C) 2014 Li Guang
> > + * Copyright (C) 2016 Xilinx Inc.
> > + * Written by Li Guang <lig.fnst@cn.fujitsu.com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms of the GNU General Public License as published by the
> > + * Free Software Foundation; either version 2 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it will be useful, but 
> > WITHOUT
> > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
> > + * for more details.
> > + *
> > + */
> > +
> > +/*
> > + * Internally inside QEMU this is a device. It is a strange device that
> > + * provides no hardware interface but allows QEMU to monkey patch memory
> > + * specified when it is created. To be able to do this it has a reset
> > + * callback that does the memory operations.
> > +
> > + * This device allows the user to monkey patch memory. To be able to do
> > + * this it needs a backend to manage the datas, the same as other
> > + * memory-related devices. In this case as the backend is so trivial we
> > + * have merged it with the frontend instead of creating and maintaining a
> > + * seperate backend.
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "qom/cpu.h"
> > +#include "hw/sysbus.h"
> > +#include "sysemu/dma.h"
> > +#include "hw/loader.h"
> > +#include "qapi/error.h"
> > +#include "hw/core/generic-loader.h"
> > +
> > +#define CPU_NONE 0xFFFFFFFF
> > +
> > +static void generic_loader_reset(void *opaque)
> > +{
> > +    GenericLoaderState *s = GENERIC_LOADER(opaque);
> > +
> > +    if (s->set_pc) {
> > +        CPUClass *cc = CPU_GET_CLASS(s->cpu);
> > +        cpu_reset(s->cpu);
> > +        if (cc) {
> > +            cc->set_pc(s->cpu, s->addr);
> > +        }
> > +    }
> > +
> > +    if (s->data_len) {
> > +        assert(s->data_len < sizeof(s->data));
> > +        dma_memory_write(s->cpu->as, s->addr, &s->data, s->data_len);
> > +    }
> > +}
> > +
> > +static void generic_loader_realize(DeviceState *dev, Error **errp)
> > +{
> > +    GenericLoaderState *s = GENERIC_LOADER(dev);
> > +    hwaddr entry;
> > +    int big_endian;
> > +    int size = 0;
> > +
> > +    s->set_pc = false;
> > +
> > +    /* Perform some error checking on the user's options */
> > +    if (s->data || s->data_len  || s->data_be) {
> > +        /* User is loading memory values */
> > +        if (s->file) {
> > +            error_setg(errp, "Specifying a file is not supported when 
> > loading "
> > +                       "memory values");
> > +            return;
> > +        } else if (s->force_raw) {
> > +            error_setg(errp, "Specifying force-raw is not supported when "
> > +                       "loading memory values");
> > +            return;
> > +        } else if (!s->data_len) {
> > +            /* We cant' check for !data here as a value of 0 is still 
> > valid. */
> > +            error_setg(errp, "Both data and data-len must be specified");
> > +            return;
> > +        } else if (s->data_len > 8) {
> > +            error_setg(errp, "data-len cannot be greater then 8 bytes");
>
> If s->data_len < 8 (like 4 or 2) ...
>
> > +            return;
> > +        }
> > +    } else if (s->file || s->force_raw)  {
> > +        /* User is loading an image */
> > +        if (s->data || s->data_len || s->data_be) {
> > +            error_setg(errp, "data can not be specified when loading an "
> > +                       "image");
> > +            return;
> > +        }
> > +        s->set_pc = true;
> > +    } else if (s->addr) {
> > +        /* User is setting the PC */
> > +        if (s->data || s->data_len || s->data_be) {
> > +            error_setg(errp, "data can not be specified when setting a "
> > +                       "program counter");
> > +            return;
> > +        } else if (!s->cpu_num) {
> > +            error_setg(errp, "cpu_num must be specified when setting a "
> > +                       "program counter");
> > +            return;
> > +        }
> > +        s->set_pc = true;
> > +    } else {
> > +        /* Did the user specify anything? */
> > +        error_setg(errp, "please include valid arguments");
> > +        return;
> > +    }
> > +
> > +    qemu_register_reset(generic_loader_reset, dev);
> > +
> > +    if (s->cpu_num != CPU_NONE) {
> > +        s->cpu = qemu_get_cpu(s->cpu_num);
> > +        if (!s->cpu) {
> > +            error_setg(errp, "Specified boot CPU#%d is nonexistent",
> > +                       s->cpu_num);
> > +            return;
> > +        }
> > +    } else {
> > +        s->cpu = first_cpu;
> > +    }
> > +
> > +#ifdef TARGET_WORDS_BIGENDIAN
> > +    big_endian = 1;
> > +#else
> > +    big_endian = 0;
> > +#endif
> > +
> > +    if (s->file) {
> > +        if (!s->force_raw) {
> > +            size = load_elf_as(s->file, NULL, NULL, &entry, NULL, NULL,
> > +                               big_endian, 0, 0, 0, s->cpu->as);
> > +
> > +            if (size < 0) {
> > +                size = load_uimage_as(s->file, &entry, NULL, NULL, NULL, 
> > NULL,
> > +                                      s->cpu->as);
> > +            }
> > +        }
> > +
> > +        if (size < 0 || s->force_raw) {
> > +            /* Default to the maximum size being the machine's ram size */
> > +            size = load_image_targphys_as(s->file, s->addr, ram_size,
> > +                                          s->cpu->as);
> > +        } else {
> > +            s->addr = entry;
> > +        }
> > +
> > +        if (size < 0) {
> > +            error_setg(errp, "Cannot load specified image %s", s->file);
> > +            return;
> > +        }
> > +    }
> > +
> > +    /* Convert the data endiannes */
> > +    if (s->data_be) {
> > +        s->data = cpu_to_be64(s->data);
> > +    } else {
> > +        s->data = cpu_to_le64(s->data);
>
> ... and if we swap, we ignore the data-len and swap 64-bit
> regardless, returning invalid data.
>
> I.e. data=0x1122, data-len=2, once swapped we get data=0x0000.
>
> Is that expected?

I don't think that's expected

Alistair