Merge branch 'for-6.4/doc' into for-linus
This commit is contained in:
Petr Mladek
commit
c9c8133080
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@ -1,8 +1,8 @@
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===========================
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Livepatch module Elf format
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Livepatch module ELF format
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===========================
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This document outlines the Elf format requirements that livepatch modules must follow.
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This document outlines the ELF format requirements that livepatch modules must follow.
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.. Table of Contents
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@ -20,17 +20,17 @@ code. So, instead of duplicating code and re-implementing what the module
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loader can already do, livepatch leverages existing code in the module
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loader to perform the all the arch-specific relocation work. Specifically,
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livepatch reuses the apply_relocate_add() function in the module loader to
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write relocations. The patch module Elf format described in this document
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write relocations. The patch module ELF format described in this document
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enables livepatch to be able to do this. The hope is that this will make
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livepatch more easily portable to other architectures and reduce the amount
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of arch-specific code required to port livepatch to a particular
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architecture.
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Since apply_relocate_add() requires access to a module's section header
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table, symbol table, and relocation section indices, Elf information is
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table, symbol table, and relocation section indices, ELF information is
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preserved for livepatch modules (see section 5). Livepatch manages its own
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relocation sections and symbols, which are described in this document. The
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Elf constants used to mark livepatch symbols and relocation sections were
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ELF constants used to mark livepatch symbols and relocation sections were
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selected from OS-specific ranges according to the definitions from glibc.
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Why does livepatch need to write its own relocations?
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@ -43,7 +43,7 @@ reject the livepatch module. Furthermore, we cannot apply relocations that
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affect modules not yet loaded at patch module load time (e.g. a patch to a
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driver that is not loaded). Formerly, livepatch solved this problem by
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embedding special "dynrela" (dynamic rela) sections in the resulting patch
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module Elf output. Using these dynrela sections, livepatch could resolve
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module ELF output. Using these dynrela sections, livepatch could resolve
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symbols while taking into account its scope and what module the symbol
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belongs to, and then manually apply the dynamic relocations. However this
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approach required livepatch to supply arch-specific code in order to write
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@ -80,7 +80,7 @@ Example:
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3. Livepatch relocation sections
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================================
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A livepatch module manages its own Elf relocation sections to apply
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A livepatch module manages its own ELF relocation sections to apply
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relocations to modules as well as to the kernel (vmlinux) at the
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appropriate time. For example, if a patch module patches a driver that is
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not currently loaded, livepatch will apply the corresponding livepatch
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@ -95,7 +95,7 @@ also possible for a livepatch module to have no livepatch relocation
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sections, as in the case of the sample livepatch module (see
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samples/livepatch).
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Since Elf information is preserved for livepatch modules (see Section 5), a
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Since ELF information is preserved for livepatch modules (see Section 5), a
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livepatch relocation section can be applied simply by passing in the
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appropriate section index to apply_relocate_add(), which then uses it to
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access the relocation section and apply the relocations.
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@ -291,19 +291,12 @@ Examples:
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Note that the 'Ndx' (Section index) for these symbols is SHN_LIVEPATCH (0xff20).
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"OS" means OS-specific.
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5. Symbol table and Elf section access
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5. Symbol table and ELF section access
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======================================
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A livepatch module's symbol table is accessible through module->symtab.
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Since apply_relocate_add() requires access to a module's section headers,
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symbol table, and relocation section indices, Elf information is preserved for
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symbol table, and relocation section indices, ELF information is preserved for
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livepatch modules and is made accessible by the module loader through
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module->klp_info, which is a klp_modinfo struct. When a livepatch module loads,
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this struct is filled in by the module loader. Its fields are documented below::
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struct klp_modinfo {
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Elf_Ehdr hdr; /* Elf header */
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Elf_Shdr *sechdrs; /* Section header table */
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char *secstrings; /* String table for the section headers */
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unsigned int symndx; /* The symbol table section index */
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};
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module->klp_info, which is a :c:type:`klp_modinfo` struct. When a livepatch module
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loads, this struct is filled in by the module loader.
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@ -352,6 +352,14 @@ struct mod_kallsyms {
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};
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#ifdef CONFIG_LIVEPATCH
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/**
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* struct klp_modinfo - ELF information preserved from the livepatch module
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*
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* @hdr: ELF header
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* @sechdrs: Section header table
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* @secstrings: String table for the section headers
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* @symndx: The symbol table section index
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*/
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struct klp_modinfo {
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Elf_Ehdr hdr;
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Elf_Shdr *sechdrs;
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@ -515,7 +523,7 @@ struct module {
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bool klp; /* Is this a livepatch module? */
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bool klp_alive;
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/* Elf information */
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/* ELF information */
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struct klp_modinfo *klp_info;
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#endif
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@ -11,7 +11,7 @@
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#include "internal.h"
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/*
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* Persist Elf information about a module. Copy the Elf header,
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* Persist ELF information about a module. Copy the ELF header,
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* section header table, section string table, and symtab section
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* index from info to mod->klp_info.
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*/
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@ -25,11 +25,11 @@ int copy_module_elf(struct module *mod, struct load_info *info)
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if (!mod->klp_info)
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return -ENOMEM;
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/* Elf header */
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/* ELF header */
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size = sizeof(mod->klp_info->hdr);
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memcpy(&mod->klp_info->hdr, info->hdr, size);
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/* Elf section header table */
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/* ELF section header table */
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size = sizeof(*info->sechdrs) * info->hdr->e_shnum;
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mod->klp_info->sechdrs = kmemdup(info->sechdrs, size, GFP_KERNEL);
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if (!mod->klp_info->sechdrs) {
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@ -37,7 +37,7 @@ int copy_module_elf(struct module *mod, struct load_info *info)
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goto free_info;
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}
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/* Elf section name string table */
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/* ELF section name string table */
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size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
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mod->klp_info->secstrings = kmemdup(info->secstrings, size, GFP_KERNEL);
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if (!mod->klp_info->secstrings) {
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@ -45,7 +45,7 @@ int copy_module_elf(struct module *mod, struct load_info *info)
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goto free_sechdrs;
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}
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/* Elf symbol section index */
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/* ELF symbol section index */
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symndx = info->index.sym;
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mod->klp_info->symndx = symndx;
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@ -17,6 +17,7 @@
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#include <linux/fs.h>
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#include <linux/kernel.h>
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#include <linux/kernel_read_file.h>
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#include <linux/kstrtox.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/elf.h>
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@ -2675,7 +2676,7 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
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int ret;
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if (strcmp(param, "async_probe") == 0) {
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if (strtobool(val, &mod->async_probe_requested))
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if (kstrtobool(val, &mod->async_probe_requested))
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mod->async_probe_requested = true;
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return 0;
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}
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@ -4,6 +4,7 @@
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*/
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#include <linux/kernel.h>
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#include <linux/kstrtox.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include <linux/module.h>
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@ -310,7 +311,7 @@ int param_set_bool(const char *val, const struct kernel_param *kp)
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if (!val) val = "1";
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/* One of =[yYnN01] */
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return strtobool(val, kp->arg);
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return kstrtobool(val, kp->arg);
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}
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EXPORT_SYMBOL(param_set_bool);
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@ -51,12 +51,11 @@ static int num_test_devs;
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/**
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* enum kmod_test_case - linker table test case
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*
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* If you add a test case, please be sure to review if you need to se
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* @need_mod_put for your tests case.
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*
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* @TEST_KMOD_DRIVER: stress tests request_module()
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* @TEST_KMOD_FS_TYPE: stress tests get_fs_type()
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*
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* If you add a test case, please be sure to review if you need to set
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* @need_mod_put for your tests case.
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*/
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enum kmod_test_case {
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__TEST_KMOD_INVALID = 0,
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@ -78,7 +77,7 @@ struct test_config {
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struct kmod_test_device;
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/**
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* kmod_test_device_info - thread info
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* struct kmod_test_device_info - thread info
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*
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* @ret_sync: return value if request_module() is used, sync request for
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* @TEST_KMOD_DRIVER
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@ -101,7 +100,7 @@ struct kmod_test_device_info {
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};
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/**
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* kmod_test_device - test device to help test kmod
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* struct kmod_test_device - test device to help test kmod
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*
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* @dev_idx: unique ID for test device
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* @config: configuration for the test
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@ -14,7 +14,7 @@ modules := $(call read-file, $(MODORDER))
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ifeq ($(KBUILD_EXTMOD),)
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dst := $(MODLIB)/kernel
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else
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INSTALL_MOD_DIR ?= extra
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INSTALL_MOD_DIR ?= updates
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dst := $(MODLIB)/$(INSTALL_MOD_DIR)
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endif
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