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Re: [PATCH, RFC, RFT] ARM relocation fixes

From: Leif Lindholm
Subject: Re: [PATCH, RFC, RFT] ARM relocation fixes
Date: Mon, 2 Dec 2013 12:28:46 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Dec 02, 2013 at 11:59:44AM +0100, Vladimir 'φ-coder/phcoder' Serbinenko 
> On 02.12.2013 11:53, Leif Lindholm wrote:
> > On Sun, Dec 01, 2013 at 07:06:32AM +0100, Vladimir 'φ-coder/phcoder' 
> > Serbinenko wrote:
> >> Current ARM relocation doesn't handle the cases when the relocation cant
> >> be satisfied directly (like thumb call over 1M of distance or jump24 to
> >> thumb mode. Attached patch adds missing tampoline and missing relocation
> >> handling to EFI code (it didn't allow to use ARM (no-Thumb) binary with
> >> EFI).
> >> I couldn't test it on either arm-efi or ARM64
> > 
> > Amusingly, I wrote the attached
> Nothing is attached to your mail. Right now could you pause work on
> */dl.c: I'm reorganising them to declare more of it as platform
> independent and unify handling (ARM dl.c is unnecessarily different from
> other versions and forget some of ELF handling)

Ok, I'll hold off.

> > on Saturday, based on a bug report
> > from Jon Masters @ Red Hat. Although an unlikely corner case, it does
> > probably need the addition of grub_arch_dl_get_tramp_got_size() from
> > your implementation in order to ensure the "veneers"[1] don't end up
> > in a heap region different to and too far away from the one the module
> > is loaded into.
> > 
> > I'll have a look and a poke on both 32- and 64-bit stuff and respond..
> > 
> > I would say the modifications to grub-mkimage for arm64 are probably
> > unnessecary: AArch64 relative branch range is +-128MB, and I don't
> > think we'll see grub kernel images that big.
> There are no changes of this kind to mkimage. I only added missing ARM
> handling and the functions which now became mkimage-specific were moved
> to it.

Well, I was referring specifically to:
--- a/util/grub-mkimagexx.c
+++ b/util/grub-mkimagexx.c
@@ -731,13 +731,13 @@ SUFFIX (relocate_addresses) (Elf_Ehdr *e, Elf_Shdr 
                   case R_AARCH64_JUMP26:
                   case R_AARCH64_CALL26:
-                      grub_err_t err;
                       sym_addr -= offset;
                       sym_addr -= SUFFIX (entry_point);
-                      err = grub_arm64_reloc_xxxx26((grub_uint32_t *)target,
+                      if (!grub_arm_64_check_xxxx26_offset (sym_addr))
+                        grub_util_error ("%s", _("CALL26 Relocation out of 
+                      grub_arm64_set_xxxx26_offset((grub_uint32_t *)target,
-                      if (err)
-                        grub_util_error ("%s", grub_errmsg);
which isn't wrong, but that offset test can only fail when your GRUB
kernel is greater than 128MB in size.


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