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hw/arm/boot: Report error if there is no fw_cfg device in the machine

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If the user provides both a BIOS/firmware image and also a guest
kernel filename, arm_setup_firmware_boot() will pass the
kernel image to the firmware via the fw_cfg device. However we
weren't checking whether there really was a fw_cfg device present,
and if there wasn't we would crash.

This crash can be provoked with a command line such as
 qemu-system-aarch64 -M raspi3 -kernel /dev/null -bios /dev/null -display none

It is currently only possible on the raspi3 machine, because unless
the machine sets info->firmware_loaded we won't call
arm_setup_firmware_boot(), and the only machines which set that are:
 * virt (has a fw-cfg device)
 * sbsa-ref (checks itself for kernel_filename && firmware_loaded)
 * raspi3 (crashes)

But this is an unfortunate beartrap to leave for future machine
model implementors, so we should handle this situation in boot.c.

Check in arm_setup_firmware_boot() whether the fw-cfg device exists
before trying to load files into it, and if it doesn't exist then
exit with a hopefully helpful error message.

Because we now handle this check in a machine-agnostic way, we
can remove the check from sbsa-ref.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/503
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20210726163351.32086-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2021-07-26 17:33:51 +01:00
parent 4d6646c7de
commit dae257394a
2 changed files with 9 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
hw/arm/boot.c
View file

@ -1243,6 +1243,15 @@ static void arm_setup_firmware_boot(ARMCPU *cpu, struct arm_boot_info *info)
bool try_decompressing_kernel;
fw_cfg = fw_cfg_find();
if (!fw_cfg) {
error_report("This machine type does not support loading both "
"a guest firmware/BIOS image and a guest kernel at "
"the same time. You should change your QEMU command "
"line to specify one or the other, but not both.");
exit(1);
}
try_decompressing_kernel = arm_feature(&cpu->env,
ARM_FEATURE_AARCH64);

7
hw/arm/sbsa-ref.c
View file

@ -691,13 +691,6 @@ static void sbsa_ref_init(MachineState *machine)
firmware_loaded = sbsa_firmware_init(sms, sysmem, secure_sysmem);
if (machine->kernel_filename && firmware_loaded) {
error_report("sbsa-ref: No fw_cfg device on this machine, "
"so -kernel option is not supported when firmware loaded, "
"please load OS from hard disk instead");
exit(1);
}
/*
* This machine has EL3 enabled, external firmware should supply PSCI
* implementation, so the QEMU's internal PSCI is disabled.