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

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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>
This commit is contained in:
Ard Biesheuvel
2020-06-08 13:07:54 +02:00
committed by mergify[bot]
parent fd708fe0e1
commit b16fd231f6
6 changed files with 68 additions and 87 deletions
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47
ArmVirtPkg/PrePi/Arm/ModuleEntryPoint.S
View File

@@ -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)
@@ -172,15 +140,24 @@ ASM_PFX(ArmPlatformPeiBootAction):
str r1, [r8]
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