x86/efi: Correct EFI boot stub use of code32_start
code32_start should point at the start of the protected mode code, and *not* at the beginning of the bzImage. This is much easier to do in assembly so document that callers of make_boot_params() need to fill out code32_start. The fallout from this bug is that we would end up relocating the image but copying the image at some offset, resulting in what appeared to be memory corruption. Reported-by: Thomas Bächler <thomas@archlinux.org> Signed-off-by: Matt Fleming <matt.fleming@intel.com>
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Matt Fleming

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396f1a08db
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7e8213c1f3
@@ -1016,6 +1016,9 @@ void setup_graphics(struct boot_params *boot_params)
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* Because the x86 boot code expects to be passed a boot_params we
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* need to create one ourselves (usually the bootloader would create
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* one for us).
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*
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* The caller is responsible for filling out ->code32_start in the
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* returned boot_params.
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*/
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struct boot_params *make_boot_params(struct efi_config *c)
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{
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@@ -1081,8 +1084,6 @@ struct boot_params *make_boot_params(struct efi_config *c)
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hdr->vid_mode = 0xffff;
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hdr->boot_flag = 0xAA55;
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hdr->code32_start = (__u64)(unsigned long)image->image_base;
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hdr->type_of_loader = 0x21;
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/* Convert unicode cmdline to ascii */
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