Re: [Minios-devel] [UNIKRAFT PATCHv4 31/43] plat/kvm: Parse command line from device tree for Arm64

[Julien Grall <julien.grall@xxxxxxx>]

Hi Wei,

On 06/07/18 10:03, Wei Chen wrote:
> QEMU/KVM can pass parameters to virtual machine through command
> line. For Arm64, this command line has been stored in device
> tree. We should parse it from device tree for further usage.
I don't think this code is KVM specific :).

> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> ---
>   plat/kvm/arm/setup.c | 32 ++++++++++++++++++++++++++++++++
>   1 file changed, 32 insertions(+)
>
> diff --git a/plat/kvm/arm/setup.c b/plat/kvm/arm/setup.c
> index 892a0a9..a881152 100644
> --- a/plat/kvm/arm/setup.c
> +++ b/plat/kvm/arm/setup.c
> @@ -36,6 +36,9 @@
>   #include <uk/assert.h>
>   #include <uk/essentials.h>
>   
> +#define MAX_CMDLINE_SIZE 1024
> +static char cmdline[MAX_CMDLINE_SIZE];
> +
>   void *_libkvmplat_dtb;
>   
>   static void _init_dtb(void *dtb_pointer)
> @@ -49,6 +52,32 @@ static void _init_dtb(void *dtb_pointer)
>         uk_printd(DLVL_INFO, "Found device tree on: %p\n", dtb_pointer);
>   }
>   
> +static void _dtb_get_cmdline(char *cmdline, size_t maxlen)
> +{
> +       int fdtchosen, len;
> +       const char *fdtcmdline;
> +
> +       /* TODO: Proper error handling */
> +       fdtchosen = fdt_path_offset(_libkvmplat_dtb, "/chosen");
> +       if (!fdtchosen)
> +               goto enocmdl;
> +       fdtcmdline = fdt_getprop(_libkvmplat_dtb, fdtchosen, "bootargs", &len);
> +       if (!fdtcmdline || (len <= 0))
> +               goto enocmdl;
> +
> +       strncpy(cmdline, fdtcmdline, MIN(maxlen, (unsigned int) len));
> +       /* ensure null termination */
> +       cmdline[((unsigned int) len - 1) <= (maxlen - 1) ?
> +               ((unsigned int) len - 1) : (maxlen - 1)] = '\0';
I don't think you need to copy the command line in an internal buffer. 
Device-Tree string are null terminated and AFAICT you keep the DT around 
for ever.
So how about turning cmdline to a pointer?

> +
> +       uk_printd(DLVL_INFO, "Command line: %s\n", cmdline);
> +       return;
> +
> +enocmdl:
> +       uk_printd(DLVL_INFO, "No command line found\n");
> +       strcpy(cmdline, CONFIG_UK_NAME);
> +}
> +
>   static void _init_cpufeatures(void)
>   {
>         /* TODO */
> @@ -61,4 +90,7 @@ void _libkvmplat_start(void *dtb_pointer)
>         _libkvmplat_init_console();
>   
>   	uk_printd(DLVL_INFO, "Entering from KVM (arm64)...\n");
> +
> +       /* Get command line from DTB */
> +       _dtb_get_cmdline(cmdline, sizeof(cmdline));
>   }
Cheers,

--
Julien Grall

_______________________________________________
Minios-devel mailing list
Minios-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/minios-devel