Re: [PATCH v10 1/3] hw/riscv: handle 32 bit CPUs kernel_addr in riscv_load_kernel()

[Alistair Francis]

On Thu, Feb 2, 2023 at 11:58 PM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> load_elf_ram_sym() will sign-extend 32 bit addresses. If a 32 bit QEMU
> guest happens to be running in a hypervisor that are using 64 bits to
> encode its address, kernel_entry can be padded with '1's and create
> problems [1].
>
> Using a translate_fn() callback in load_elf_ram_sym() to filter the
> padding from the address doesn't work. A more detailed explanation can
> be found in [2]. The short version is that glue(load_elf, SZ), from
> include/hw/elf_ops.h, will calculate 'pentry' (mapped into the
> 'kernel_load_base' var in riscv_load_Kernel()) before using
> translate_fn(), and will not recalculate it after executing it. This
> means that the callback does not prevent the padding from
> kernel_load_base to appear.
>
> Let's instead use a kernel_low var to capture the 'lowaddr' value from
> load_elf_ram_sim(), and return it when we're dealing with 32 bit CPUs.
>
> [1] https://lists.gnu.org/archive/html/qemu-devel/2023-01/msg02281.html
> [2] https://lists.gnu.org/archive/html/qemu-devel/2023-02/msg00099.html
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  hw/riscv/boot.c            | 15 +++++++++++----
>  hw/riscv/microchip_pfsoc.c |  3 ++-
>  hw/riscv/opentitan.c       |  3 ++-
>  hw/riscv/sifive_e.c        |  3 ++-
>  hw/riscv/sifive_u.c        |  3 ++-
>  hw/riscv/spike.c           |  3 ++-
>  hw/riscv/virt.c            |  3 ++-
>  include/hw/riscv/boot.h    |  1 +
>  8 files changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
> index c7e0e50bd8..5ec6d32165 100644
> --- a/hw/riscv/boot.c
> +++ b/hw/riscv/boot.c
> @@ -174,11 +174,12 @@ target_ulong riscv_load_firmware(const char 
> *firmware_filename,
>  }
>
>  target_ulong riscv_load_kernel(MachineState *machine,
> +                               RISCVHartArrayState *harts,
>                                 target_ulong kernel_start_addr,
>                                 symbol_fn_t sym_cb)
>  {
>      const char *kernel_filename = machine->kernel_filename;
> -    uint64_t kernel_load_base, kernel_entry;
> +    uint64_t kernel_load_base, kernel_entry, kernel_low;
>
>      g_assert(kernel_filename != NULL);
>
> @@ -189,10 +190,16 @@ target_ulong riscv_load_kernel(MachineState *machine,
>       * the (expected) load address load address. This allows kernels to have
>       * separate SBI and ELF entry points (used by FreeBSD, for example).
>       */
> -    if (load_elf_ram_sym(kernel_filename, NULL, NULL, NULL,
> -                         NULL, &kernel_load_base, NULL, NULL, 0,
> +    if (load_elf_ram_sym(kernel_filename, NULL, NULL, NULL, NULL,
> +                         &kernel_load_base, &kernel_low, NULL, 0,
>                           EM_RISCV, 1, 0, NULL, true, sym_cb) > 0) {
> -        return kernel_load_base;
> +        kernel_entry = kernel_load_base;
> +
> +        if (riscv_is_32bit(harts)) {
> +            kernel_entry = kernel_low;
> +        }
> +
> +        return kernel_entry;
>      }
>
>      if (load_uimage_as(kernel_filename, &kernel_entry, NULL, NULL,
> diff --git a/hw/riscv/microchip_pfsoc.c b/hw/riscv/microchip_pfsoc.c
> index 2b91e49561..712625d2a4 100644
> --- a/hw/riscv/microchip_pfsoc.c
> +++ b/hw/riscv/microchip_pfsoc.c
> @@ -629,7 +629,8 @@ static void 
> microchip_icicle_kit_machine_init(MachineState *machine)
>          kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc.u_cpus,
>                                                           firmware_end_addr);
>
> -        kernel_entry = riscv_load_kernel(machine, kernel_start_addr, NULL);
> +        kernel_entry = riscv_load_kernel(machine, &s->soc.u_cpus,
> +                                         kernel_start_addr, NULL);
>
>          if (machine->initrd_filename) {
>              riscv_load_initrd(machine, kernel_entry);
> diff --git a/hw/riscv/opentitan.c b/hw/riscv/opentitan.c
> index 353f030d80..7fe4fb5628 100644
> --- a/hw/riscv/opentitan.c
> +++ b/hw/riscv/opentitan.c
> @@ -101,7 +101,8 @@ static void opentitan_board_init(MachineState *machine)
>      }
>
>      if (machine->kernel_filename) {
> -        riscv_load_kernel(machine, memmap[IBEX_DEV_RAM].base, NULL);
> +        riscv_load_kernel(machine, &s->soc.cpus,
> +                          memmap[IBEX_DEV_RAM].base, NULL);
>      }
>  }
>
> diff --git a/hw/riscv/sifive_e.c b/hw/riscv/sifive_e.c
> index 3e3f4b0088..1a7d381514 100644
> --- a/hw/riscv/sifive_e.c
> +++ b/hw/riscv/sifive_e.c
> @@ -114,7 +114,8 @@ static void sifive_e_machine_init(MachineState *machine)
>                            memmap[SIFIVE_E_DEV_MROM].base, 
> &address_space_memory);
>
>      if (machine->kernel_filename) {
> -        riscv_load_kernel(machine, memmap[SIFIVE_E_DEV_DTIM].base, NULL);
> +        riscv_load_kernel(machine, &s->soc.cpus,
> +                          memmap[SIFIVE_E_DEV_DTIM].base, NULL);
>      }
>  }
>
> diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
> index d3ab7a9cda..71be442a50 100644
> --- a/hw/riscv/sifive_u.c
> +++ b/hw/riscv/sifive_u.c
> @@ -598,7 +598,8 @@ static void sifive_u_machine_init(MachineState *machine)
>          kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc.u_cpus,
>                                                           firmware_end_addr);
>
> -        kernel_entry = riscv_load_kernel(machine, kernel_start_addr, NULL);
> +        kernel_entry = riscv_load_kernel(machine, &s->soc.u_cpus,
> +                                         kernel_start_addr, NULL);
>
>          if (machine->initrd_filename) {
>              riscv_load_initrd(machine, kernel_entry);
> diff --git a/hw/riscv/spike.c b/hw/riscv/spike.c
> index cc3f6dac17..1fa91167ab 100644
> --- a/hw/riscv/spike.c
> +++ b/hw/riscv/spike.c
> @@ -305,7 +305,8 @@ static void spike_board_init(MachineState *machine)
>          kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc[0],
>                                                           firmware_end_addr);
>
> -        kernel_entry = riscv_load_kernel(machine, kernel_start_addr,
> +        kernel_entry = riscv_load_kernel(machine, &s->soc[0],
> +                                         kernel_start_addr,
>                                           htif_symbol_callback);
>
>          if (machine->initrd_filename) {
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index a061151a6f..d0531cc641 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -1277,7 +1277,8 @@ static void virt_machine_done(Notifier *notifier, void 
> *data)
>          kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc[0],
>                                                           firmware_end_addr);
>
> -        kernel_entry = riscv_load_kernel(machine, kernel_start_addr, NULL);
> +        kernel_entry = riscv_load_kernel(machine, &s->soc[0],
> +                                         kernel_start_addr, NULL);
>
>          if (machine->initrd_filename) {
>              riscv_load_initrd(machine, kernel_entry);
> diff --git a/include/hw/riscv/boot.h b/include/hw/riscv/boot.h
> index 511390f60e..6295316afb 100644
> --- a/include/hw/riscv/boot.h
> +++ b/include/hw/riscv/boot.h
> @@ -44,6 +44,7 @@ target_ulong riscv_load_firmware(const char 
> *firmware_filename,
>                                   hwaddr firmware_load_addr,
>                                   symbol_fn_t sym_cb);
>  target_ulong riscv_load_kernel(MachineState *machine,
> +                               RISCVHartArrayState *harts,
>                                 target_ulong firmware_end_addr,
>                                 symbol_fn_t sym_cb);
>  void riscv_load_initrd(MachineState *machine, uint64_t kernel_entry);
> --
> 2.39.1
>
>