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Diffstat (limited to 'llvm/docs/Extensions.rst')
| -rw-r--r-- | llvm/docs/Extensions.rst | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/llvm/docs/Extensions.rst b/llvm/docs/Extensions.rst index bad72c6c..d8fb87b 100644 --- a/llvm/docs/Extensions.rst +++ b/llvm/docs/Extensions.rst @@ -581,6 +581,26 @@ This section stores pairs of (jump table address, number of entries). This information is useful for tools that need to statically reconstruct the control flow of executables. +``SHT_LLVM_CFI_JUMP_TABLE`` Section (CFI jump table) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +This section contains the instructions that make up a `CFI jump table`_. +It is expected to be ``SHF_ALLOC`` and may be laid out like a normal +section. The ``SHT_LLVM_CFI_JUMP_TABLE`` section type gives the linker +permission to modify the section in ways that would not normally be +permitted, in order to optimize calls via the jump table. + +Each ``sh_entsize`` sized slice of a section of this type containing +exactly one relocation may be considered to be a jump table entry +that branches to the target of the relocation. This allows the linker +to replace the jump table entry with the function body if it is small +enough, or if the function is the last function in the jump table. + +A section of this type does not have to be placed according to its +name. The linker may place the section in whichever output section it +sees fit (generally the section that would provide the best locality). + +.. _CFI jump table: https://clang.llvm.org/docs/ControlFlowIntegrityDesign.html#forward-edge-cfi-for-indirect-function-calls + CodeView-Dependent ------------------ |