lkml.org 
[lkml]   [2011]   [Aug]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 8/9] x86, efi: EFI boot stub support
Date
Matt Fleming <matt@console-pimps.org> writes:
> +
> + status = efi_call_phys3(sys_table->boottime->allocate_pool,
> + EFI_LOADER_DATA, sizeof(*idt),
> + (void **)&idt);
> + if (status != EFI_SUCCESS)
> + goto fail;
> +
> + idt->size = 0;
> + idt->address = 0;
> +
> + status = make_boot_params(boot_params, image, handle);
> + if (status != EFI_SUCCESS)
> + goto fail;
> +
> + memset((char *)gdt->address, 0x0, gdt->size);
> + desc = (u64 *)gdt->address;
> +
> + /*
> + * 4Gb - (0x100000*0x1000 = 4Gb)
> + * base address=0
> + * code read/exec
> + * granularity=4096, 386 (+5th nibble of limit)
> + */
> + desc[2] = 0x00cf9a000000ffff;
> +
> + /*
> + * 4Gb - (0x100000*0x1000 = 4Gb)
> + * base address=0
> + * data read/write
> + * granularity=4096, 386 (+5th nibble of limit)
> + */
> + desc[3] = 0x00cf92000000ffff;
> +
> + /* Task segment value */
> + desc[4] = 0x0080890000000000;

The code would benefit from more variables/defines and less magic numbers.

I assume this is all virtual, otherwise it would be really scary.

> + asm volatile ("lidt %0" :: "m" (*idt));
> + asm volatile ("lgdt %0" :: "m" (*gdt));
> +
> + asm volatile("cli");

::: "memory" to avoid moving

> +
> + return boot_params;
> +fail:
> + return NULL;

Does the caller actually something useful here for NULL? Better to have
messages when any of this fails.

> +int memcmp(const void *s1, const void *s2, size_t len)
> +{
> + u8 diff;
> + asm("repe; cmpsb; setnz %0"
> + : "=qm" (diff), "+D" (s1), "+S" (s2), "+c" (len));

This doesn't describe to gcc that the inline assembler
reads s1 and s2. At the minimum add a memory clobber.

> +
> +/**
> + * strlen - Find the length of a string
> + * @s: The string to be sized
> + */
> +size_t strlen(const char *s)
> +{
> + const char *sc;
> +
> + for (sc = s; *sc != '\0'; ++sc)
> + /* nothing */;
> + return sc - s;
> +}

Why not just link in/#include lib/string.c ?


-Andi
--
ak@linux.intel.com -- Speaking for myself only


\
 
 \ /
  Last update: 2011-08-11 20:11    [W:0.081 / U:3.104 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site