2e349337d3
We need to workaround the fact that MAP_PRIVATE when passed a file descriptor doesn't work the way we expect. We can't change the permissions on our mmap to PROT_WRITE if the original executable doesn't have PROT_WRITE. Because of this, we need to construct our ELFDynamicObject using the actual virtual address of the .dynamic section, instead of using the offset into the ELFImage that was actually getting modified by accident ...somehow. Not clear what was going on.
90 lines
3.2 KiB
C++
90 lines
3.2 KiB
C++
#pragma once
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#include <LibELF/ELFDynamicObject.h>
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#include <LibELF/ELFImage.h>
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#include <LibELF/exec_elf.h>
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#include <mman.h>
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#include <AK/OwnPtr.h>
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#include <AK/RefCounted.h>
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#include <AK/String.h>
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#define ALIGN_ROUND_UP(x, align) ((((size_t)(x)) + align - 1) & (~(align - 1)))
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class ELFDynamicLoader : public RefCounted<ELFDynamicLoader> {
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public:
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static NonnullRefPtr<ELFDynamicLoader> construct(const char* filename, int fd, size_t file_size);
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~ELFDynamicLoader();
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bool is_valid() const { return m_valid; }
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// Load a full ELF image from file into the current process and create an ELFDynamicObject
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// from the SHT_DYNAMIC in the file.
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bool load_from_image(unsigned flags);
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// Stage 2 of loading: relocations and init functions
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// Assumes that the program headers have been loaded and that m_dynamic_object is initialized
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// Splitting loading like this allows us to use the same code to relocate a main executable as an elf binary
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bool load_stage_2(unsigned flags);
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// Intended for use by dlsym or other internal methods
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void* symbol_for_name(const char*);
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void dump();
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// Will be called from _fixup_plt_entry, as part of the PLT trampoline
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Elf32_Addr patch_plt_entry(u32 relocation_offset);
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private:
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class ProgramHeaderRegion {
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public:
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void set_program_header(const Elf32_Phdr& header) { m_program_header = header; }
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// Information from ELF Program header
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u32 type() const { return m_program_header.p_type; }
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u32 flags() const { return m_program_header.p_flags; }
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u32 offset() const { return m_program_header.p_offset; }
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VirtualAddress desired_load_address() const { return VirtualAddress(m_program_header.p_vaddr); }
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u32 size_in_memory() const { return m_program_header.p_memsz; }
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u32 size_in_image() const { return m_program_header.p_filesz; }
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u32 alignment() const { return m_program_header.p_align; }
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u32 mmap_prot() const;
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bool is_readable() const { return flags() & PF_R; }
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bool is_writable() const { return flags() & PF_W; }
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bool is_executable() const { return flags() & PF_X; }
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bool is_tls_template() const { return type() == PT_TLS; }
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bool is_load() const { return type() == PT_LOAD; }
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bool is_dynamic() const { return type() == PT_DYNAMIC; }
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u32 required_load_size() { return ALIGN_ROUND_UP(m_program_header.p_memsz, m_program_header.p_align); }
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private:
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Elf32_Phdr m_program_header; // Explictly a copy of the PHDR in the image
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};
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explicit ELFDynamicLoader(const char* filename, int fd, size_t file_size);
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explicit ELFDynamicLoader(Elf32_Dyn* dynamic_location, Elf32_Addr load_address);
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// Stage 1
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void load_program_headers(const ELFImage& elf_image);
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// Stage 2
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void do_relocations();
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void setup_plt_trampoline();
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void call_object_init_functions();
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String m_filename;
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size_t m_file_size { 0 };
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int m_image_fd { -1 };
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void* m_file_mapping { nullptr };
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bool m_valid { true };
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OwnPtr<ELFDynamicObject> m_dynamic_object;
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VirtualAddress m_text_segment_load_address;
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size_t m_text_segment_size;
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VirtualAddress m_tls_segment_address;
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VirtualAddress m_dynamic_section_address;
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};
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