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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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49
ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S
View File

@@ -9,40 +9,6 @@
#include <AsmMacroIoLibV8.h>
ASM_FUNC(_ModuleEntryPoint)
//
// We are built as a ET_DYN PIE executable, so we need to process all
// relative relocations regardless of whether or not we are executing from
// the same offset we were linked at. This is only possible if we are
// running from RAM.
//
adr x8, __reloc_base
adr x9, __reloc_start
adr x10, __reloc_end
.Lreloc_loop:
cmp x9, x10
bhs .Lreloc_done
//
// AArch64 uses the ELF64 RELA format, which means each entry in the
// relocation table consists of
//
// UINT64 offset : the relative offset of the value that needs to
// be relocated
// UINT64 info : relocation type and symbol index (the latter is
// not used for R_AARCH64_RELATIVE relocations)
// UINT64 addend : value to be added to the value being relocated
//
ldp x11, x12, [x9], #24 // read offset into x11 and info into x12
cmp x12, #0x403 // check info == R_AARCH64_RELATIVE?
bne .Lreloc_loop // not a relative relocation? then skip
ldr x12, [x9, #-8] // read addend into x12
add x12, x12, x8 // add reloc base to addend to get relocated value
str x12, [x11, x8] // write relocated value at offset
b .Lreloc_loop
.Lreloc_done:
bl ASM_PFX(DiscoverDramFromDt)
// Get ID of this CPU in Multicore system
@@ -170,15 +136,24 @@ ASM_PFX(DiscoverDramFromDt):
str x1, [x8]
str x7, [x9]
//
// 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 x0, x7
adr x1, PeCoffLoaderImageReadFromMemory
mov sp, x7
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 x0, x28
adr x1, PcdGet64 (PcdSystemMemoryBase)
adr x2, PcdGet64 (PcdSystemMemorySize)
mov sp, x7
bl FindMemnode
cbz x0, .Lout