diff mbox series

[v3,6/6] efi: restrict arm/arm64 linux loader initrd placement

Message ID 20180627171720.27028-7-leif.lindholm@linaro.org
State New
Headers show
Series efi: arm linux loader unification and correctness | expand

Commit Message

Leif Lindholm June 27, 2018, 5:17 p.m. UTC
The 32-bit arm Linux kernel is built as a zImage, which self-decompresses
down to near start of RAM. In order for an initrd/initramfs to be
accessible, it needs to be placed within the first ~768MB of RAM.
The initrd loader built into the kernel EFI stub restricts this down to
512MB for simplicity - so enable the same restriction in grub.

For arm64, the requirement is within a 1GB aligned 32GB window also
covering the (runtime) kernel image. Since the EFI stub loader itself
will attempt to relocate to near start of RAM, force initrd to be loaded
completely within the first 32GB of RAM.

Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>

---
 grub-core/loader/arm64/linux.c | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

-- 
2.11.0


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Comments

Daniel Kiper July 6, 2018, 4 p.m. UTC | #1
On Wed, Jun 27, 2018 at 06:17:20PM +0100, Leif Lindholm wrote:
> The 32-bit arm Linux kernel is built as a zImage, which self-decompresses

> down to near start of RAM. In order for an initrd/initramfs to be

> accessible, it needs to be placed within the first ~768MB of RAM.

> The initrd loader built into the kernel EFI stub restricts this down to

> 512MB for simplicity - so enable the same restriction in grub.

>

> For arm64, the requirement is within a 1GB aligned 32GB window also

> covering the (runtime) kernel image. Since the EFI stub loader itself

> will attempt to relocate to near start of RAM, force initrd to be loaded

> completely within the first 32GB of RAM.

>

> Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>

> ---

>  grub-core/loader/arm64/linux.c | 39 ++++++++++++++++++++++++++++++++++++++-

>  1 file changed, 38 insertions(+), 1 deletion(-)

>

> diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c

> index 577fbda54..0d550182f 100644

> --- a/grub-core/loader/arm64/linux.c

> +++ b/grub-core/loader/arm64/linux.c

> @@ -193,6 +193,42 @@ grub_linux_unload (void)

>    return GRUB_ERR_NONE;

>  }

>

> +/*

> + * This function returns a pointer to a legally allocated initrd buffer,

> + * or NULL if unsuccessful

> + */

> +static void *

> +allocate_initrd_mem (int initrd_pages)

> +{

> +  grub_addr_t max_addr;

> +

> +  if (grub_efi_get_ram_base (&max_addr) != GRUB_ERR_NONE)

> +    return NULL;

> +

> +  /*

> +   * As per linux/Documentation/arm/Booting

> +   * ARM initrd needs to be covered by kernel linear mapping,

> +   * so place it in the first 512MB of DRAM.

> +   *

> +   * As per linux/Documentation/arm64/booting.txt

> +   * ARM64 initrd needs to be contained entirely within a 1GB aligned window

> +   * of up to 32GB of size that covers the kernel image as well.

> +   * Since the EFI stub loader will attempt to load the kernel near start of

> +   * RAM, place the buffer in the first 32GB of RAM.

> +   */

> +#ifdef __arm__

> +#define INITRD_MAX_ADDRESS_OFFSET (512U * 1024 * 1024)

> +#else /* __aarch64__ */

> +#define INITRD_MAX_ADDRESS_OFFSET (32ULL * 1024 * 1024 * 1024)

> +#endif


May I ask you to move these definitions together with the comment before
the allocate_initrd_mem(). Or even to the beginning of the file just
behind GRUB_MOD_LICENSE(). I prefer the latter. Though I am not
insisting on it.

Daniel

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Leif Lindholm July 6, 2018, 4:33 p.m. UTC | #2
On Fri, Jul 06, 2018 at 06:00:11PM +0200, Daniel Kiper wrote:
> On Wed, Jun 27, 2018 at 06:17:20PM +0100, Leif Lindholm wrote:

> > The 32-bit arm Linux kernel is built as a zImage, which self-decompresses

> > down to near start of RAM. In order for an initrd/initramfs to be

> > accessible, it needs to be placed within the first ~768MB of RAM.

> > The initrd loader built into the kernel EFI stub restricts this down to

> > 512MB for simplicity - so enable the same restriction in grub.

> >

> > For arm64, the requirement is within a 1GB aligned 32GB window also

> > covering the (runtime) kernel image. Since the EFI stub loader itself

> > will attempt to relocate to near start of RAM, force initrd to be loaded

> > completely within the first 32GB of RAM.

> >

> > Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>

> > ---

> >  grub-core/loader/arm64/linux.c | 39 ++++++++++++++++++++++++++++++++++++++-

> >  1 file changed, 38 insertions(+), 1 deletion(-)

> >

> > diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c

> > index 577fbda54..0d550182f 100644

> > --- a/grub-core/loader/arm64/linux.c

> > +++ b/grub-core/loader/arm64/linux.c

> > @@ -193,6 +193,42 @@ grub_linux_unload (void)

> >    return GRUB_ERR_NONE;

> >  }

> >

> > +/*

> > + * This function returns a pointer to a legally allocated initrd buffer,

> > + * or NULL if unsuccessful

> > + */

> > +static void *

> > +allocate_initrd_mem (int initrd_pages)

> > +{

> > +  grub_addr_t max_addr;

> > +

> > +  if (grub_efi_get_ram_base (&max_addr) != GRUB_ERR_NONE)

> > +    return NULL;

> > +

> > +  /*

> > +   * As per linux/Documentation/arm/Booting

> > +   * ARM initrd needs to be covered by kernel linear mapping,

> > +   * so place it in the first 512MB of DRAM.

> > +   *

> > +   * As per linux/Documentation/arm64/booting.txt

> > +   * ARM64 initrd needs to be contained entirely within a 1GB aligned window

> > +   * of up to 32GB of size that covers the kernel image as well.

> > +   * Since the EFI stub loader will attempt to load the kernel near start of

> > +   * RAM, place the buffer in the first 32GB of RAM.

> > +   */

> > +#ifdef __arm__

> > +#define INITRD_MAX_ADDRESS_OFFSET (512U * 1024 * 1024)

> > +#else /* __aarch64__ */

> > +#define INITRD_MAX_ADDRESS_OFFSET (32ULL * 1024 * 1024 * 1024)

> > +#endif

> 

> May I ask you to move these definitions together with the comment before

> the allocate_initrd_mem(). Or even to the beginning of the file just

> behind GRUB_MOD_LICENSE(). I prefer the latter. Though I am not

> insisting on it.


I'm OK with either. I stuck it here because it is information that is
_only_ relevant to this particular piece of code. So my preference
leans the other way. Will update for v4.

/
    Leif

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diff mbox series

Patch

diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c
index 577fbda54..0d550182f 100644
--- a/grub-core/loader/arm64/linux.c
+++ b/grub-core/loader/arm64/linux.c
@@ -193,6 +193,42 @@  grub_linux_unload (void)
   return GRUB_ERR_NONE;
 }
 
+/*
+ * This function returns a pointer to a legally allocated initrd buffer,
+ * or NULL if unsuccessful
+ */
+static void *
+allocate_initrd_mem (int initrd_pages)
+{
+  grub_addr_t max_addr;
+
+  if (grub_efi_get_ram_base (&max_addr) != GRUB_ERR_NONE)
+    return NULL;
+
+  /*
+   * As per linux/Documentation/arm/Booting
+   * ARM initrd needs to be covered by kernel linear mapping,
+   * so place it in the first 512MB of DRAM.
+   *
+   * As per linux/Documentation/arm64/booting.txt
+   * ARM64 initrd needs to be contained entirely within a 1GB aligned window
+   * of up to 32GB of size that covers the kernel image as well.
+   * Since the EFI stub loader will attempt to load the kernel near start of
+   * RAM, place the buffer in the first 32GB of RAM.
+   */
+#ifdef __arm__
+#define INITRD_MAX_ADDRESS_OFFSET (512U * 1024 * 1024)
+#else /* __aarch64__ */
+#define INITRD_MAX_ADDRESS_OFFSET (32ULL * 1024 * 1024 * 1024)
+#endif
+
+  max_addr += INITRD_MAX_ADDRESS_OFFSET - 1;
+
+  return grub_efi_allocate_pages_real (max_addr, initrd_pages,
+				       GRUB_EFI_ALLOCATE_MAX_ADDRESS,
+				       GRUB_EFI_LOADER_DATA);
+}
+
 static grub_err_t
 grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
 		 int argc, char *argv[])
@@ -221,7 +257,8 @@  grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
   grub_dprintf ("linux", "Loading initrd\n");
 
   initrd_pages = (GRUB_EFI_BYTES_TO_PAGES (initrd_size));
-  initrd_mem = grub_efi_allocate_any_pages (initrd_pages);
+  initrd_mem = allocate_initrd_mem (initrd_pages);
+
   if (!initrd_mem)
     {
       grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));