diff --git a/llvm/docs/Extensions.rst b/llvm/docs/Extensions.rstindex bad72c6ca8295..d8fb87b6998ad 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 ------------------diff --git a/llvm/include/llvm/BinaryFormat/ELF.h b/llvm/include/llvm/BinaryFormat/ELF.hindex ebb257ab33821..b9e38801d880f 100644--- a/llvm/include/llvm/BinaryFormat/ELF.h+++ b/llvm/include/llvm/BinaryFormat/ELF.h@@ -1159,6 +1159,7 @@ enum : unsigned {   SHT_LLVM_OFFLOADING = 0x6fff4c0b,         // LLVM device offloading data.   SHT_LLVM_LTO = 0x6fff4c0c,                // .llvm.lto for fat LTO.   SHT_LLVM_JT_SIZES = 0x6fff4c0d,           // LLVM jump tables sizes.+  SHT_LLVM_CFI_JUMP_TABLE = 0x6fff4c0e,     // LLVM CFI jump table.   // Android's experimental support for SHT_RELR sections.   // https://android.googlesource.com/platform/bionic/+/b7feec74547f84559a1467aca02708ff61346d2a/libc/include/elf.h#512   SHT_ANDROID_RELR = 0x6fffff00,   // Relocation entries; only offsets.diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cppindex ec8b40261a6ca..c7c3df330fc94 100644--- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp+++ b/llvm/lib/MC/MCParser/ELFAsmParser.cpp@@ -571,7 +571,7 @@ bool ELFAsmParser::parseSectionArguments(bool IsPush, SMLoc loc) {         return TokError("expected end of directive");     }-    if (Mergeable)+    if (Mergeable || TypeName == "llvm_cfi_jump_table")       if (parseMergeSize(Size))         return true;     if (Flags & ELF::SHF_LINK_ORDER)@@ -637,6 +637,8 @@ bool ELFAsmParser::parseSectionArguments(bool IsPush, SMLoc loc) {       Type = ELF::SHT_LLVM_LTO;     else if (TypeName == "llvm_jt_sizes")       Type = ELF::SHT_LLVM_JT_SIZES;+    else if (TypeName == "llvm_cfi_jump_table")+      Type = ELF::SHT_LLVM_CFI_JUMP_TABLE;     else if (TypeName.getAsInteger(0, Type))       return TokError("unknown section type");   }diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cppindex ff99dc25abe07..28a7040ea8d56 100644--- a/llvm/lib/Object/ELF.cpp+++ b/llvm/lib/Object/ELF.cpp@@ -321,6 +321,7 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_OFFLOADING);     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LTO);     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_JT_SIZES)+    STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CFI_JUMP_TABLE)     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef);diff --git a/llvm/test/MC/AsmParser/llvm_section_types.s b/llvm/test/MC/AsmParser/llvm_section_types.sindex 147b1499d2b88..1e644ced853b3 100644--- a/llvm/test/MC/AsmParser/llvm_section_types.s+++ b/llvm/test/MC/AsmParser/llvm_section_types.s@@ -17,6 +17,8 @@ .byte 1 .section    .section8,"",@llvm_lto .byte 1+.section    .section9,"",@llvm_cfi_jump_table,1+.byte 1  # CHECK:        Name: .section1 # CHECK-NEXT:   Type: SHT_LLVM_BB_ADDR_MAP@@ -34,3 +36,6 @@ # CHECK-NEXT:   Type: SHT_LLVM_OFFLOADING # CHECK:        Name: .section8 # CHECK-NEXT:   Type: SHT_LLVM_LTO+# CHECK:        Name: .section9+# CHECK-NEXT:   Type: SHT_LLVM_CFI_JUMP_TABLE+# CHECK:        EntrySize: 1

diff --git a/llvm/docs/Extensions.rst b/llvm/docs/Extensions.rstindex bad72c6ca8295..d8fb87b6998ad 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 ------------------diff --git a/llvm/include/llvm/BinaryFormat/ELF.h b/llvm/include/llvm/BinaryFormat/ELF.hindex ebb257ab33821..b9e38801d880f 100644--- a/llvm/include/llvm/BinaryFormat/ELF.h+++ b/llvm/include/llvm/BinaryFormat/ELF.h@@ -1159,6 +1159,7 @@ enum : unsigned {   SHT_LLVM_OFFLOADING = 0x6fff4c0b,         // LLVM device offloading data.   SHT_LLVM_LTO = 0x6fff4c0c,                // .llvm.lto for fat LTO.   SHT_LLVM_JT_SIZES = 0x6fff4c0d,           // LLVM jump tables sizes.+  SHT_LLVM_CFI_JUMP_TABLE = 0x6fff4c0e,     // LLVM CFI jump table.   // Android's experimental support for SHT_RELR sections.   // https://android.googlesource.com/platform/bionic/+/b7feec74547f84559a1467aca02708ff61346d2a/libc/include/elf.h#512   SHT_ANDROID_RELR = 0x6fffff00,   // Relocation entries; only offsets.diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cppindex ec8b40261a6ca..c7c3df330fc94 100644--- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp+++ b/llvm/lib/MC/MCParser/ELFAsmParser.cpp@@ -571,7 +571,7 @@ bool ELFAsmParser::parseSectionArguments(bool IsPush, SMLoc loc) {         return TokError("expected end of directive");     }-    if (Mergeable)+    if (Mergeable || TypeName == "llvm_cfi_jump_table")       if (parseMergeSize(Size))         return true;     if (Flags & ELF::SHF_LINK_ORDER)@@ -637,6 +637,8 @@ bool ELFAsmParser::parseSectionArguments(bool IsPush, SMLoc loc) {       Type = ELF::SHT_LLVM_LTO;     else if (TypeName == "llvm_jt_sizes")       Type = ELF::SHT_LLVM_JT_SIZES;+    else if (TypeName == "llvm_cfi_jump_table")+      Type = ELF::SHT_LLVM_CFI_JUMP_TABLE;     else if (TypeName.getAsInteger(0, Type))       return TokError("unknown section type");   }diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cppindex ff99dc25abe07..28a7040ea8d56 100644--- a/llvm/lib/Object/ELF.cpp+++ b/llvm/lib/Object/ELF.cpp@@ -321,6 +321,7 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_OFFLOADING);     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LTO);     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_JT_SIZES)+    STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_CFI_JUMP_TABLE)     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef);diff --git a/llvm/test/MC/AsmParser/llvm_section_types.s b/llvm/test/MC/AsmParser/llvm_section_types.sindex 147b1499d2b88..1e644ced853b3 100644--- a/llvm/test/MC/AsmParser/llvm_section_types.s+++ b/llvm/test/MC/AsmParser/llvm_section_types.s@@ -17,6 +17,8 @@ .byte 1 .section    .section8,"",@llvm_lto .byte 1+.section    .section9,"",@llvm_cfi_jump_table,1+.byte 1  # CHECK:        Name: .section1 # CHECK-NEXT:   Type: SHT_LLVM_BB_ADDR_MAP@@ -34,3 +36,6 @@ # CHECK-NEXT:   Type: SHT_LLVM_OFFLOADING # CHECK:        Name: .section8 # CHECK-NEXT:   Type: SHT_LLVM_LTO+# CHECK:        Name: .section9+# CHECK-NEXT:   Type: SHT_LLVM_CFI_JUMP_TABLE+# CHECK:        EntrySize: 1