3d34053af6
For
mov name@GOTPCREL(%rip), %reg
test %reg, name@GOTPCREL(%rip)
binop name@GOTPCREL(%rip), %reg
where binop is one of adc, add, and, cmp, or, sbb, sub, xor
instructions, add
`R_X86_64_REX2_GOTPCRELX`/`R_X86_64_CODE_4_GOTPCRELX` = 43
if the instruction starts at 4 bytes before the relocation offset. It
similar to R_X86_64_GOTPCRELX.
Linker can treat `R_X86_64_REX2_GOTPCRELX`/`R_X86_64_CODE_4_GOTPCRELX`
as `R_X86_64_GOTPCREL` or convert the above instructions to
lea name(%rip), %reg
mov $name, %reg
test $name, %reg
binop $name, %reg
if the first byte of the instruction at the relocation `offset - 4` is
`0xd5` (namely, encoded w/ REX2 prefix) when possible.
Binutils patch:
3d5a60de52
Binutils mailthread:
https://sourceware.org/pipermail/binutils/2023-December/131462.html
ABI discussion: https://groups.google.com/g/x86-64-abi/c/KbzaNHRB6QU
Blog: https://kanrobert.github.io/rfc/All-about-APX-relocation
59 lines
1.8 KiB
ArmAsm
59 lines
1.8 KiB
ArmAsm
# RUN: llvm-mc -filetype=obj -triple x86_64 %s -o %t
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# RUN: llvm-objdump --no-print-imm-hex -dr %t | FileCheck %s
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# RUN: llvm-readelf -s %t | FileCheck %s --check-prefix=SYM
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# RUN: not llvm-mc -filetype=obj -triple x86_64 --defsym ERR=1 %s 2>&1 | FileCheck %s --check-prefix=ERR
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## If a fixup symbol is equated to an undefined symbol, convert the fixup
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## to be against the target symbol, even if there is a variant (@PLT).
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# CHECK: callq {{.*}}
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# CHECK-NEXT: R_X86_64_PLT32 __GI_memcpy-0x4
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# CHECK: movabsq $0, %rax
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# CHECK-NEXT: R_X86_64_64 __GI_memcpy+0x2
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memcpy = __GI_memcpy
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call memcpy@PLT
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movabsq $memcpy+2, %rax
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# CHECK: movq (%rip), %rax
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# CHECK-NEXT: R_X86_64_REX_GOTPCRELX abs-0x4
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# CHECK: movq (%rip), %r16
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# CHECK-NEXT: R_X86_64_REX2_GOTPCRELX abs-0x4
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movq abs@GOTPCREL(%rip), %rax
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movq abs@GOTPCREL(%rip), %r16
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abs = 42
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# CHECK: movabsq $0, %rbx
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# CHECK-NEXT: R_X86_64_64 data_alias
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.globl data_alias
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.set data_alias, data
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movabsq $data_alias, %rbx
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## A local alias to a defined symbol still references a section symbol.
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# CHECK: movabsq $0, %rbx
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# CHECK-NEXT: R_X86_64_64 .data+0x1
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.set data_alias_l, data
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movabsq $data_alias_l, %rbx
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.data
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.byte 0
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.globl data
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data:
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.ifdef ERR
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.text
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## Note, GNU as emits a relocation for this erroneous fixup.
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# ERR: {{.*}}.s:[[#@LINE+2]]:1: error: expected relocatable expression
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memcpy_plus_1 = __GI_memcpy+1
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call memcpy_plus_1@PLT
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.endif
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## Redirected symbols do not have a symbol table entry.
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# SYM: NOTYPE LOCAL DEFAULT UND
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# SYM-NEXT: NOTYPE LOCAL DEFAULT ABS abs
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# SYM-NEXT: NOTYPE LOCAL DEFAULT 4 data_alias_l
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# SYM-NEXT: SECTION LOCAL DEFAULT 4 .data
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# SYM-NEXT: NOTYPE GLOBAL DEFAULT UND __GI_memcpy
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# SYM-NEXT: NOTYPE GLOBAL DEFAULT 4 data_alias
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# SYM-NEXT: NOTYPE GLOBAL DEFAULT 4 data
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# SYM-NOT: {{.}}
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