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[COFF, ARM64] Handle ADRP immediate offsets in relocations
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Also handle overflow correctly in LDR/STR relocations. Even if the
offset range of a 8 byte LDR instruction is 15 bit (even if the immediate
itself is 12 bit) due to a 3 bit shift, only include up to 12 bits of offset
after doing the relocation, by limiting the range of the immediate by the
number of shifted bits.

Differential Revision: https://reviews.llvm.org/D35792

llvm-svn: 309175
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@mstorsjo
mstorsjo committed Jul 26, 2017
1 parent 853ce87 commit 38608c0
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Showing 2 changed files with 57 additions and 25 deletions.
34 changes: 25 additions & 9 deletions lld/COFF/Chunks.cpp
View file
Expand Up @@ -167,21 +167,38 @@ void SectionChunk::applyRelARM(uint8_t *Off, uint16_t Type, OutputSection *OS,
}
}

static void applyArm64Addr(uint8_t *Off, uint64_t Imm) {
// Interpret the existing immediate value as a byte offset to the
// target symbol, then update the instruction with the immediate as
// the page offset from the current instruction to the target.
static void applyArm64Addr(uint8_t *Off, uint64_t S, uint64_t P) {
uint32_t Orig = read32le(Off);
uint64_t Imm = ((Orig >> 29) & 0x3) | ((Orig >> 3) & 0x1FFFFC);
S += Imm;
Imm = (S >> 12) - (P >> 12);
uint32_t ImmLo = (Imm & 0x3) << 29;
uint32_t ImmHi = (Imm & 0x1FFFFC) << 3;
uint64_t Mask = (0x3 << 29) | (0x1FFFFC << 3);
write32le(Off, (read32le(Off) & ~Mask) | ImmLo | ImmHi);
write32le(Off, (Orig & ~Mask) | ImmLo | ImmHi);
}

// Update the immediate field in a AARCH64 ldr, str, and add instruction.
static void applyArm64Imm(uint8_t *Off, uint64_t Imm) {
// Optionally limit the range of the written immediate by one or more bits
// (RangeLimit).
static void applyArm64Imm(uint8_t *Off, uint64_t Imm, uint32_t RangeLimit) {
uint32_t Orig = read32le(Off);
Imm += (Orig >> 10) & 0xFFF;
Orig &= ~(0xFFF << 10);
write32le(Off, Orig | ((Imm & 0xFFF) << 10));
write32le(Off, Orig | ((Imm & (0xFFF >> RangeLimit)) << 10));
}

// Add the 12 bit page offset to the existing immediate.
// Ldr/str instructions store the opcode immediate scaled
// by the load/store size (giving a larger range for larger
// loads/stores). The immediate is always (both before and after
// fixing up the relocation) stored scaled similarly.
// Even if larger loads/stores have a larger range, limit the
// effective offset to 12 bit, since it is intended to be a
// page offset.
static void applyArm64Ldr(uint8_t *Off, uint64_t Imm) {
uint32_t Orig = read32le(Off);
uint32_t Size = Orig >> 30;
Expand All @@ -191,14 +208,14 @@ static void applyArm64Ldr(uint8_t *Off, uint64_t Imm) {
Size += 4;
if ((Imm & ((1 << Size) - 1)) != 0)
fatal("misaligned ldr/str offset");
applyArm64Imm(Off, Imm >> Size);
applyArm64Imm(Off, Imm >> Size, Size);
}

void SectionChunk::applyRelARM64(uint8_t *Off, uint16_t Type, OutputSection *OS,
uint64_t S, uint64_t P) const {
switch (Type) {
case IMAGE_REL_ARM64_PAGEBASE_REL21: applyArm64Addr(Off, (S >> 12) - (P >> 12)); break;
case IMAGE_REL_ARM64_PAGEOFFSET_12A: applyArm64Imm(Off, S & 0xfff); break;
case IMAGE_REL_ARM64_PAGEBASE_REL21: applyArm64Addr(Off, S, P); break;
case IMAGE_REL_ARM64_PAGEOFFSET_12A: applyArm64Imm(Off, S & 0xfff, 0); break;
case IMAGE_REL_ARM64_PAGEOFFSET_12L: applyArm64Ldr(Off, S & 0xfff); break;
case IMAGE_REL_ARM64_BRANCH26: or32(Off, ((S - P) & 0x0FFFFFFC) >> 2); break;
case IMAGE_REL_ARM64_ADDR32: add32(Off, S + Config->ImageBase); break;
Expand Down Expand Up @@ -403,10 +420,9 @@ void ImportThunkChunkARM::writeTo(uint8_t *Buf) const {
}

void ImportThunkChunkARM64::writeTo(uint8_t *Buf) const {
int64_t PageOff = (ImpSymbol->getRVA() >> 12) - (RVA >> 12);
int64_t Off = ImpSymbol->getRVA() & 0xfff;
memcpy(Buf + OutputSectionOff, ImportThunkARM64, sizeof(ImportThunkARM64));
applyArm64Addr(Buf + OutputSectionOff, PageOff);
applyArm64Addr(Buf + OutputSectionOff, ImpSymbol->getRVA(), RVA);
applyArm64Ldr(Buf + OutputSectionOff + 4, Off);
}

Expand Down
48 changes: 32 additions & 16 deletions lld/test/COFF/arm64-relocs-imports.test
View file
Expand Up @@ -29,17 +29,19 @@
# BEFORE: 50: 00 01 00 fd str d0, [x8]
# BEFORE: 54: 00 01 80 3d str q0, [x8]
# BEFORE: 58: 00 05 40 f9 ldr x0, [x8, #8]
# BEFORE: 5c: e0 03 1f 2a mov w0, wzr
# BEFORE: 60: fe 07 41 f8 ldr x30, [sp], #16
# BEFORE: 64: c0 03 5f d6 ret
# BEFORE: 68: 08 00 00 00 <unknown>
# BEFORE: 6c: 00 00 00 00 <unknown>
# BEFORE: 5c: 20 1a 01 b0 adrp x0, #36982784
# BEFORE: 60: 00 fc 4f f9 ldr x0, [x0, #8184]
# BEFORE: 64: e0 03 1f 2a mov w0, wzr
# BEFORE: 68: fe 07 41 f8 ldr x30, [sp], #16
# BEFORE: 6c: c0 03 5f d6 ret
# BEFORE: 70: 08 00 00 00 <unknown>
# BEFORE: 74: 00 00 00 00 <unknown>

# AFTER: Disassembly of section .text:
# AFTER: 140002000: fe 0f 1f f8 str x30, [sp, #-16]!
# AFTER: 140002004: e0 ff ff f0 adrp x0, #-4096
# AFTER: 140002008: 00 18 00 91 add x0, x0, #6
# AFTER: 14000200c: 19 00 00 94 bl #100
# AFTER: 14000200c: 1b 00 00 94 bl #108
# AFTER: 140002010: 00 21 40 39 ldrb w0, [x8, #8]
# AFTER: 140002014: 00 11 40 79 ldrh w0, [x8, #8]
# AFTER: 140002018: 00 09 40 b9 ldr w0, [x8, #8]
Expand All @@ -59,14 +61,16 @@
# AFTER: 140002050: 00 09 00 fd str d0, [x8, #16]
# AFTER: 140002054: 00 05 80 3d str q0, [x8, #16]
# AFTER: 140002058: 00 09 40 f9 ldr x0, [x8, #16]
# AFTER: 14000205c: e0 03 1f 2a mov w0, wzr
# AFTER: 140002060: fe 07 41 f8 ldr x30, [sp], #16
# AFTER: 140002064: c0 03 5f d6 ret
# AFTER: 140002068: 10 10 00 40 <unknown>
# AFTER: 14000206c: 01 00 00 00 <unknown>
# AFTER: 140002070: 10 00 00 b0 adrp x16, #4096
# AFTER: 140002074: 10 1e 40 f9 ldr x16, [x16, #56]
# AFTER: 140002078: 00 02 1f d6 br x16
# AFTER: 14000205c: 00 00 00 b0 adrp x0, #4096
# AFTER: 140002060: 00 fc 47 f9 ldr x0, [x0, #4088]
# AFTER: 140002064: e0 03 1f 2a mov w0, wzr
# AFTER: 140002068: fe 07 41 f8 ldr x30, [sp], #16
# AFTER: 14000206c: c0 03 5f d6 ret
# AFTER: 140002070: 10 10 00 40 <unknown>
# AFTER: 140002074: 01 00 00 00 <unknown>
# AFTER: 140002078: 10 00 00 b0 adrp x16, #4096
# AFTER: 14000207c: 10 1e 40 f9 ldr x16, [x16, #56]
# AFTER: 140002080: 00 02 1f d6 br x16

--- !COFF
header:
Expand All @@ -76,7 +80,7 @@ sections:
- Name: .text
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 4
SectionData: FE0F1FF80000009000080091000000940001403900014079000140B9000140F90001003900010079000100B9000100F90001403D0001407D000140BD000140FD0001C03D0001003D0001007D000100BD000100FD0001803D000540F9E0031F2AFE0741F8C0035FD60800000000000000
SectionData: FE0F1FF80000009000080091000000940001403900014079000140B9000140F90001003900010079000100B9000100F90001403D0001407D000140BD000140FD0001C03D0001003D0001007D000100BD000100FD0001803D000540F9201A01B000FC4FF9E0031F2AFE0741F8C0035FD60800000000000000
Relocations:
- VirtualAddress: 4
SymbolName: .Lstr
Expand Down Expand Up @@ -144,7 +148,13 @@ sections:
- VirtualAddress: 88
SymbolName: .Lglobal
Type: 7
- VirtualAddress: 104
- VirtualAddress: 92
SymbolName: .Lglobal16
Type: 4
- VirtualAddress: 96
SymbolName: .Lglobal0
Type: 7
- VirtualAddress: 112
SymbolName: .Lglobal
Type: 14
- Name: .data
Expand Down Expand Up @@ -208,6 +218,12 @@ symbols:
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
- Name: .Lglobal0
Value: 0
SectionNumber: 4
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_STATIC
- Name: function
Value: 0
SectionNumber: 0
Expand Down

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