f17c4e01e9
When a module is loaded, calls out to the kernel go via a stub which is generated at runtime. One of these stubs is used to call _mcount(), which is the default target of tracing calls generated by the compiler with -pg. If dynamic ftrace is enabled (which it typically is), another stub is used to call ftrace_caller(), which is the target of tracing calls when ftrace is actually active. ftrace then wants to disable the calls to _mcount() at module startup, and enable/disable the calls to ftrace_caller() when enabling/disabling tracing - all of these it does by patching the code. As part of that code patching, the ftrace code wants to confirm that the branch it is about to modify, is in fact a call to a module stub which calls _mcount() or ftrace_caller(). Currently it does that by inspecting the instructions and confirming they are what it expects. Although that works, the code to do it is pretty intricate because it requires lots of knowledge about the exact format of the stub. We can make that process easier by marking the generated stubs with a magic value, and then looking for that magic value. Altough this is not as rigorous as the current method, I believe it is sufficient in practice. Reviewed-by: Balbir Singh <bsingharora@gmail.com> Reviewed-by: Torsten Duwe <duwe@suse.de> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
103 lines
2.6 KiB
C
103 lines
2.6 KiB
C
#ifndef _ASM_POWERPC_MODULE_H
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#define _ASM_POWERPC_MODULE_H
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#ifdef __KERNEL__
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/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/list.h>
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#include <asm/bug.h>
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#include <asm-generic/module.h>
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#ifndef __powerpc64__
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/*
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* Thanks to Paul M for explaining this.
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*
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* PPC can only do rel jumps += 32MB, and often the kernel and other
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* modules are furthur away than this. So, we jump to a table of
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* trampolines attached to the module (the Procedure Linkage Table)
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* whenever that happens.
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*/
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struct ppc_plt_entry {
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/* 16 byte jump instruction sequence (4 instructions) */
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unsigned int jump[4];
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};
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#endif /* __powerpc64__ */
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struct mod_arch_specific {
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#ifdef __powerpc64__
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unsigned int stubs_section; /* Index of stubs section in module */
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unsigned int toc_section; /* What section is the TOC? */
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bool toc_fixed; /* Have we fixed up .TOC.? */
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#ifdef CONFIG_DYNAMIC_FTRACE
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unsigned long toc;
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unsigned long tramp;
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#endif
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#else /* powerpc64 */
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/* Indices of PLT sections within module. */
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unsigned int core_plt_section;
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unsigned int init_plt_section;
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#ifdef CONFIG_DYNAMIC_FTRACE
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unsigned long tramp;
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#endif
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#endif /* powerpc64 */
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/* List of BUG addresses, source line numbers and filenames */
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struct list_head bug_list;
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struct bug_entry *bug_table;
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unsigned int num_bugs;
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};
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/*
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* Select ELF headers.
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* Make empty section for module_frob_arch_sections to expand.
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*/
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#ifdef __powerpc64__
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# ifdef MODULE
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asm(".section .stubs,\"ax\",@nobits; .align 3; .previous");
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# endif
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#else
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# ifdef MODULE
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asm(".section .plt,\"ax\",@nobits; .align 3; .previous");
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asm(".section .init.plt,\"ax\",@nobits; .align 3; .previous");
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# endif /* MODULE */
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#endif
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#ifdef CONFIG_DYNAMIC_FTRACE
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# ifdef MODULE
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asm(".section .ftrace.tramp,\"ax\",@nobits; .align 3; .previous");
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# endif /* MODULE */
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#endif
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int module_trampoline_target(struct module *mod, unsigned long trampoline,
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unsigned long *target);
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#ifdef CONFIG_DYNAMIC_FTRACE
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int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs);
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#else
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static inline int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
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{
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return 0;
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}
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#endif
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struct exception_table_entry;
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void sort_ex_table(struct exception_table_entry *start,
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struct exception_table_entry *finish);
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#if defined(CONFIG_MODVERSIONS) && defined(CONFIG_PPC64)
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#define ARCH_RELOCATES_KCRCTAB
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#define reloc_start PHYSICAL_START
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#endif
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#endif /* __KERNEL__ */
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#endif /* _ASM_POWERPC_MODULE_H */
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