f901499b11
Detect trailing unmarked code after CFI-bounded predecessors (__BOLT_FDE_FUNC* or symbols whose FDE address range equals their size) and promote it into separate BinaryFunction objects named __BOLT_UNMARKED_TAILat<addr>. A predecessor is only considered when: - the target is AArch64 - it is not a pseudo or fragment function - it has slack beyond its recorded size (MaxSize > Size) - it is CFI-bounded - no function is already registered at the tail start address The trailing region is measured conservatively and we bail out (leaving the slack attached to the predecessor) when: - the tail range is not fully contained in the predecessor's origin section - a data marker ($d) or a constant island overlaps the region (data-in-code) - disassembly fails or yields a zero-length instruction - after trimming trailing padding, the tail is empty (i.e. it contained only padding) or does not end in a return - any bytes past the decoded code are non-zero, i.e. not pure zero padding. The bug was introduced in commit [cd27741](cd27741c11)
111 lines
3 KiB
ArmAsm
111 lines
3 KiB
ArmAsm
## Promote unmarked code after a CFI-bounded predecessor into __BOLT_UNMARKED_TAIL.
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## Covers:
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## 1) FDE-only region (no symtab entry; BOLT names it __BOLT_FDE_FUNC* or .text/N)
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## 2) Named function (FDE range == symbol size) -> named_sub + tail
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## Caller is in a separate section; -Wl,-q keeps PC-relative relocs on the bl.
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# RUN: llvm-mc -filetype=obj -triple aarch64-unknown-unknown %s -o %t.o
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# RUN: %clang %cflags %t.o -pie -Wl,-q -o %t.exe
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# RUN: llvm-bolt %t.exe -o %t.bolt --print-disasm -v=1 2>&1 | FileCheck %s
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# CHECK-COUNT-3: BOLT-WARNING: detected executable code after CFI-bounded function
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# CHECK-SAME: creating synthetic function __BOLT_UNMARKED_TAILat
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# CHECK-SAME: Consider adding a symbol or FDE for this code.
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## Scenario 1a: FDE-only predecessor at the section start (named after .text).
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## The tail has trailing filler nops after its ret: they are trimmed from the
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## callable Size but remain part of MaxSize slack.
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# CHECK: Binary Function ".text/{{[0-9]+}}" after disassembly
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# CHECK: Size : 0x14
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# CHECK: MaxSize : 0x14
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# CHECK: Binary Function "{{.*}}__BOLT_UNMARKED_TAIL{{.*}}" after disassembly
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# CHECK: Size : 0x8
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# CHECK: MaxSize : 0x10
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## Scenario 1b: FDE-only predecessor discovered from the FDE alone.
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# CHECK: Binary Function "__BOLT_FDE_FUNC{{.*}}" after disassembly
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# CHECK: Size : 0x14
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# CHECK: MaxSize : 0x14
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# CHECK: Binary Function "{{.*}}__BOLT_UNMARKED_TAIL{{.*}}" after disassembly
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# CHECK: Size : 0x8
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# CHECK: MaxSize : 0x8
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## Scenario 2: named predecessor (FDE address range matches .size).
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# CHECK: Binary Function "named_sub" after disassembly
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# CHECK: Size : 0x14
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# CHECK: MaxSize : 0x14
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# CHECK: Binary Function "{{.*}}__BOLT_UNMARKED_TAIL{{.*}}" after disassembly
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# CHECK: Size : 0x10
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# CHECK: MaxSize : 0x10
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# CHECK-COUNT-3: bl __BOLT_UNMARKED_TAILat{{.*}}
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.section .text.fdeonly,"ax",@progbits
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## Scenario 1a: FDE-only predecessor at the section start (no symbol table entry).
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.Lfde_sub:
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.cfi_startproc
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stp x29, x30, [sp, #-16]!
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mov x29, sp
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mov w0, #42
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ldp x29, x30, [sp], #16
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ret
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.cfi_endproc
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.Ltail_after_fde:
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nop
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ret
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nop
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nop
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## Scenario 1b: identical FDE-only region, not at the section start.
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.Lfde_sub2:
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.cfi_startproc
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stp x29, x30, [sp, #-16]!
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mov x29, sp
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mov w0, #42
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ldp x29, x30, [sp], #16
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ret
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.cfi_endproc
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.Ltail_after_fde2:
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nop
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ret
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.section .text.named,"ax",@progbits
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## Scenario 2: named predecessor (FDE address range matches .size).
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.globl named_sub
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.type named_sub, %function
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named_sub:
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.cfi_startproc
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stp x29, x30, [sp, #-16]!
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mov x29, sp
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mov w0, #7
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ldp x29, x30, [sp], #16
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ret
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.cfi_endproc
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.size named_sub, .-named_sub
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.Ltail_after_named:
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mov x0, x0
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mov w1, #7
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add w0, w0, w1
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ret
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.section .text.entry,"ax",@progbits
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.globl _start
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.type _start, %function
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_start:
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.cfi_startproc
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stp x29, x30, [sp, #-16]!
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mov x29, sp
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bl .Ltail_after_fde
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bl .Ltail_after_fde2
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bl .Ltail_after_named
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ldp x29, x30, [sp], #16
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mov w0, #0
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ret
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.cfi_endproc
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.size _start, .-_start
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