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| -rw-r--r-- | Documentation/livepatch/module-elf-format.rst | 33 |
1 files changed, 8 insertions, 25 deletions
diff --git a/Documentation/livepatch/module-elf-format.rst b/Documentation/livepatch/module-elf-format.rst index 2a591e6f8e6c..7347638895a0 100644 --- a/Documentation/livepatch/module-elf-format.rst +++ b/Documentation/livepatch/module-elf-format.rst @@ -7,15 +7,8 @@ This document outlines the Elf format requirements that livepatch modules must f .. Table of Contents - 1. Background and motivation - 2. Livepatch modinfo field - 3. Livepatch relocation sections - 3.1 Livepatch relocation section format - 4. Livepatch symbols - 4.1 A livepatch module's symbol table - 4.2 Livepatch symbol format - 5. Architecture-specific sections - 6. Symbol table and Elf section access +.. contents:: :local: + 1. Background and motivation ============================ @@ -217,11 +210,11 @@ module->symtab. ===================================== Normally, a stripped down copy of a module's symbol table (containing only "core" symbols) is made available through module->symtab (See layout_symtab() -in kernel/module.c). For livepatch modules, the symbol table copied into memory -on module load must be exactly the same as the symbol table produced when the -patch module was compiled. This is because the relocations in each livepatch -relocation section refer to their respective symbols with their symbol indices, -and the original symbol indices (and thus the symtab ordering) must be +in kernel/module/kallsyms.c). For livepatch modules, the symbol table copied +into memory on module load must be exactly the same as the symbol table produced +when the patch module was compiled. This is because the relocations in each +livepatch relocation section refer to their respective symbols with their symbol +indices, and the original symbol indices (and thus the symtab ordering) must be preserved in order for apply_relocate_add() to find the right symbol. For example, take this particular rela from a livepatch module::: @@ -298,17 +291,7 @@ Examples: Note that the 'Ndx' (Section index) for these symbols is SHN_LIVEPATCH (0xff20). "OS" means OS-specific. -5. Architecture-specific sections -================================= -Architectures may override arch_klp_init_object_loaded() to perform -additional arch-specific tasks when a target module loads, such as applying -arch-specific sections. On x86 for example, we must apply per-object -.altinstructions and .parainstructions sections when a target module loads. -These sections must be prefixed with ".klp.arch.$objname." so that they can -be easily identified when iterating through a patch module's Elf sections -(See arch/x86/kernel/livepatch.c for a complete example). - -6. Symbol table and Elf section access +5. Symbol table and Elf section access ====================================== A livepatch module's symbol table is accessible through module->symtab. |