ArmVirtPkg/PrePi: use standard PeCoff routines for self-relocation

Instead of having a GCC specific routine to perform self-relocation
based on ELF metadata, use the PE/COFF metadata and the existing
PeCoff library routines. This reduces the amount of bespoke assembler
code that is a burden to maintain, and is not portable across the set
of toolchains we support.

This does require some special care, as we have no control over how
the C code references global symbols, so we need to emit these
references from the calling assembler code. Otherwise, they may be
emitted as absolute references, in which case they need to be fixed
up themselves, leading to a circular dependency.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Acked-by: Sami Mujawar <Sami.Mujawar@arm.com>

1 files changed, 12 insertions, 35 deletions

diff --git a/ArmVirtPkg/PrePi/Arm/ModuleEntryPoint.S b/ArmVirtPkg/PrePi/Arm/ModuleEntryPoint.S
index 72d756fdb5..f0536c65eb 100644
--- a/ArmVirtPkg/PrePi/Arm/ModuleEntryPoint.S
+++ b/ArmVirtPkg/PrePi/Arm/ModuleEntryPoint.S
@@ -9,38 +9,6 @@
 #include <AsmMacroIoLib.h>

 

 ASM_FUNC(_ModuleEntryPoint)

-  //

-  // We are built as a ET_DYN PIE executable, so we need to process all

-  // relative relocations if we are executing from a different offset than we

-  // were linked at. This is only possible if we are running from RAM.

-  //

-  ADRL  (r4, __reloc_base)

-  ADRL  (r5, __reloc_start)

-  ADRL  (r6, __reloc_end)

-

-.Lreloc_loop:

-  cmp   r5, r6

-  bhs   .Lreloc_done

-

-  //

-  // AArch32 uses the ELF32 REL format, which means each entry in the

-  // relocation table consists of

-  //

-  //   UINT32 offset          : the relative offset of the value that needs to

-  //                            be relocated

-  //   UINT32 info            : relocation type and symbol index (the latter is

-  //                            not used for R_ARM_RELATIVE relocations)

-  //

-  ldrd  r8, r9, [r5], #8      // read offset into r8 and info into r9

-  cmp   r9, #23               // check info == R_ARM_RELATIVE?

-  bne   .Lreloc_loop          // not a relative relocation? then skip

-

-  ldr   r9, [r8, r4]          // read addend into r9

-  add   r9, r9, r1            // add image base to addend to get relocated value

-  str   r9, [r8, r4]          // write relocated value at offset

-  b     .Lreloc_loop

-.Lreloc_done:

-

   // Do early platform specific actions

   bl    ASM_PFX(ArmPlatformPeiBootAction)

 

@@ -173,14 +141,23 @@ ASM_PFX(ArmPlatformPeiBootAction):
   str   r5, [r7]

 

   //

+  // The runtime address may be different from the link time address so fix

+  // up the PE/COFF relocations. Since we are calling a C function, use the

+  // window at the beginning of the FD image as a temp stack.

+  //

+  mov   r0, r5

+  ADRL  (r1, PeCoffLoaderImageReadFromMemory)

+  mov   sp, r5

+  bl    RelocatePeCoffImage

+

+  //

   // Discover the memory size and offset from the DTB, and record in the

   // respective PCDs. This will also return false if a corrupt DTB is

-  // encountered. Since we are calling a C function, use the window at the

-  // beginning of the FD image as a temp stack.

+  // encountered.

   //

+  mov   r0, r10

   ADRL  (r1, PcdGet64 (PcdSystemMemoryBase))

   ADRL  (r2, PcdGet64 (PcdSystemMemorySize))

-  mov   sp, r5

   bl    FindMemnode

   teq   r0, #0

   beq   .Lout