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SubjectRe: [PATCH v2 10/10] x86, efi: EFI boot stub support
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On Thu, 2011-09-15 at 14:44 +0200, Maarten Lankhorst wrote:
> Thanks, that makes much more sense. The man page makes mention
> of extra arguments, but it kind of looked like the way to pass it was by
> using -u -@ - which didn't work of course. :)
>
> So for reference:
> efibootmgr -L 'EFI Native Linux Boot' -l '\vmlinuz.efi' -d /dev/sdb -u root=/dev/sdb2 console=ttyS0,115200n8
>
> or as ASCII (reads much prettier in efibootmgr -v)
> efibootmgr -L 'EFI Native Linux Boot' -l '\vmlinuz.efi' -d /dev/sdb root=/dev/sdb2 console=ttyS0,115200n8
>
> This is the fixed patch I'm using for booting native linux kernel,
> with passing args tested for UCS-2 and ASCII. It seems that
> options_size can be halved safely, otherwise too much data is
> copied from input.

Thanks for looking at this Maarten. I've been staring at this code for
far too long to notice buglets like this ;-)

> I keep the first word, since otherwise the first argument is stripped off,
> and it's probably harmless for the kernel to read something like
> \vmlinuz.efi when you don't do a direct boot.
>
> Signed-off-by: Maarten Lankhorst <m.b.lankhorst@gmail.com>
>
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index 6c34828..f77f9f5 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -619,12 +619,12 @@ static efi_status_t make_boot_params(struct boot_params *boot_params,
> unsigned long cmdline;
> u8 nr_entries;
> u16 *s2;
> - u8 *s1;
> + u8 *s1, *s2_8;
> int i;
>
> hdr->type_of_loader = 0x21;
>
> - status = low_alloc(options_size, 1, &cmdline);
> + status = low_alloc(options_size+1, 1, &cmdline);
> if (status != EFI_SUCCESS)
> goto fail;

If no options were passed to the stub then we really don't want to do
the allocation at all. Speaking of 'options_size', have you tested the
values that get passed in from image->load_options? Running with the
OVMF firmware under qemu I get sizes that are always larger than the
NUL-byte in the argument string. For example, executing "bzImage foo"
results in image->load_options being 38!

Remember that ->options_size represents 16-bit characters and cmdline is
going to be ASCII. options_size will always be larger than the value we
need, so there's no need for the +1. At the moment we're actually
allocating too much memory and that needs to be fixed.

> @@ -633,27 +633,29 @@ static efi_status_t make_boot_params(struct boot_params *boot_params,
> /* Convert unicode cmdline to ascii */
> s1 = (u8 *)(unsigned long)hdr->cmd_line_ptr;
> s2 = (u16 *)options;
> + s2_8 = (u8*)options;
>
> - if (s2 && options_size) {
> - /* Skip first word, that's the kernel name */
> - while (*s2 && *s2 != ' ' && *s2 != '\n') {
> - options_size--;
> - s2++;
> - }
> -
> - /* skip space */
> - if (*s2 == ' ') {
> - options_size--;
> - s2++;
> - }
> -
> - while (options_size-- != 0) {
> + if (options_size < 2 || !s2) {
> + *s1 = '\0';
> + } else if (s2_8[1] && s2_8[1] < 0x80 && s2_8[0] < 0x80) {
> + /* Passed as ASCII */
> + s2 = NULL;
> + memcpy(s1, s2_8, options_size);
> + hdr->cmdline_size = options_size;
> + } else {
> + options_size /= 2; /* Passed as UCS-2 */
> + while (options_size-- != 0 && *s2) {
> *s1++ = *s2++;
> hdr->cmdline_size++;
> }
> -
> *s1 = '\0';
> + s1 = (u8 *)(unsigned long)hdr->cmd_line_ptr;
> }
> + if (hdr->cmdline_size && s1[hdr->cmdline_size - 1] == '\0')
> + hdr->cmdline_size--;
> + if (hdr->cmdline_size && s1[hdr->cmdline_size - 1] == '\n')
> + hdr->cmdline_size--;
> + s1[hdr->cmdline_size] = '\0';
>
> hdr->ramdisk_image = 0;
> hdr->ramdisk_size = 0;

Hmm... I'm really not convinced that we need to support ASCII cmdline
arguments, sorry. efibootmgr has support for UCS-2, so that's what
should be used.

Thanks for the review!

--
Matt Fleming, Intel Open Source Technology Center



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