f4f4caab0e
I wanted a tiny scriptable meltdown proof way to run userspace programs and visualize how program execution impacts memory. It helps to explain how things like Actually Portable Executable works. It can show you how the GCC generated code is going about manipulating matrices and more. I didn't feel fully comfortable with Qemu and Bochs because I'm not smart enough to understand them. I wanted something like gVisor but with much stronger levels of assurances. I wanted a single binary that'll run, on all major operating systems with an embedded GPL barrier ZIP filesystem that is tiny enough to transpile to JavaScript and run in browsers too. https://justine.storage.googleapis.com/emulator625.mp4
125 lines
4.9 KiB
C
125 lines
4.9 KiB
C
#ifndef COSMOPOLITAN_LIBC_ELF_H_
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#define COSMOPOLITAN_LIBC_ELF_H_
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#ifndef __STRICT_ANSI__
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#include "libc/bits/safemacros.h"
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#include "libc/elf/def.h"
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#include "libc/elf/struct/ehdr.h"
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#include "libc/elf/struct/phdr.h"
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#include "libc/elf/struct/shdr.h"
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#include "libc/elf/struct/sym.h"
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#include "libc/limits.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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COSMOPOLITAN_C_START_
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/*───────────────────────────────────────────────────────────────────────────│─╗
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│ cosmopolitan § executable & linkable format ─╬─│┼
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╚────────────────────────────────────────────────────────────────────────────│*/
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struct MappedFile;
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Elf64_Ehdr *mapelfread(const char *, struct MappedFile *);
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char *getelfstringtable(const Elf64_Ehdr *, size_t);
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Elf64_Sym *getelfsymboltable(const Elf64_Ehdr *, size_t, Elf64_Xword *);
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Elf64_Shdr *getelfsectionbyaddress(const Elf64_Ehdr *, size_t, void *);
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forceinline void checkelfaddress(const Elf64_Ehdr *elf, size_t mapsize,
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intptr_t addr, size_t addrsize) {
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#if !(TRUSTWORTHY + ELF_TRUSTWORTHY + 0) || ELF_UNTRUSTWORTHY + 0
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if (addr < (intptr_t)elf || addr + addrsize > (intptr_t)elf + mapsize) {
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abort();
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}
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#endif
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}
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static inline bool iself64binary(const Elf64_Ehdr *elf, size_t mapsize) {
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return mapsize >= sizeof(Elf64_Ehdr) &&
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memcmp(elf->e_ident, ELFMAG, 4) == 0 &&
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(elf->e_ident[EI_CLASS] == ELFCLASSNONE ||
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elf->e_ident[EI_CLASS] == ELFCLASS64);
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}
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static inline bool iselfsymbolcontent(const Elf64_Sym *sym) {
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return sym->st_size > 0 && (ELF64_ST_TYPE(sym->st_info) == STT_FUNC ||
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ELF64_ST_TYPE(sym->st_info) == STT_OBJECT);
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}
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static inline Elf64_Phdr *getelfsegmentheaderaddress(const Elf64_Ehdr *elf,
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size_t mapsize,
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unsigned i) {
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intptr_t addr =
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((intptr_t)elf + (intptr_t)elf->e_phoff + (intptr_t)elf->e_phentsize * i);
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checkelfaddress(elf, mapsize, addr, elf->e_phentsize);
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return (Elf64_Phdr *)addr;
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}
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static inline Elf64_Shdr *getelfsectionheaderaddress(const Elf64_Ehdr *elf,
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size_t mapsize,
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Elf64_Half i) {
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intptr_t addr =
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((intptr_t)elf + (intptr_t)elf->e_shoff + (intptr_t)elf->e_shentsize * i);
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checkelfaddress(elf, mapsize, addr, elf->e_shentsize);
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return (Elf64_Shdr *)addr;
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}
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static inline void *getelfsectionaddress(const Elf64_Ehdr *elf, size_t mapsize,
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const Elf64_Shdr *shdr) {
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intptr_t addr, size;
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addr = (intptr_t)elf + (intptr_t)shdr->sh_offset;
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size = (intptr_t)shdr->sh_size;
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checkelfaddress(elf, mapsize, addr, size);
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return (void *)addr;
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}
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static inline char *getelfsectionnamestringtable(const Elf64_Ehdr *elf,
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size_t mapsize) {
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if (!elf->e_shoff || !elf->e_shentsize) return NULL;
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return getelfsectionaddress(
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elf, mapsize, getelfsectionheaderaddress(elf, mapsize, elf->e_shstrndx));
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}
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static inline void getelfvirtualaddressrange(const Elf64_Ehdr *elf,
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size_t elfsize,
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intptr_t *out_start,
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intptr_t *out_end) {
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unsigned i;
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Elf64_Phdr *phdr;
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intptr_t start, end, pstart, pend;
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start = INTPTR_MAX;
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end = 0;
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for (i = 0; i < elf->e_phnum; ++i) {
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phdr = getelfsegmentheaderaddress(elf, elfsize, i);
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if (phdr->p_type != PT_LOAD) continue;
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pstart = phdr->p_vaddr;
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pend = phdr->p_vaddr + phdr->p_memsz;
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if (pstart < start) start = pstart;
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if (pend > end) end = pend;
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}
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if (out_start) *out_start = start;
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if (out_end) *out_end = end;
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}
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static inline char *getelfstring(const Elf64_Ehdr *elf, size_t mapsize,
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const char *strtab, Elf64_Word rva) {
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intptr_t addr = (intptr_t)strtab + rva;
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#if !(TRUSTWORTHY + ELF_TRUSTWORTHY + 0)
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checkelfaddress(elf, mapsize, addr, 0);
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checkelfaddress(elf, mapsize, addr,
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strnlen((char *)addr, (intptr_t)elf + mapsize - addr) + 1);
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#endif
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return (char *)addr;
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}
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static inline const char *getelfsectionname(const Elf64_Ehdr *elf,
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size_t mapsize, Elf64_Shdr *shdr) {
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if (!elf || !shdr) return NULL;
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return getelfstring(elf, mapsize, getelfsectionnamestringtable(elf, mapsize),
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shdr->sh_name);
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}
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COSMOPOLITAN_C_END_
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* !ANSI */
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#endif /* COSMOPOLITAN_LIBC_ELF_H_ */
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