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https://github.com/jart/cosmopolitan.git
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0c630d95b5
The build/bootstrap/ar.com program is now tinier. This change reduces its size from 140kb to 53kb. Nothing was traded away. Cosmopolitan Ar performance is now 2x better than llvm-ar largely thanks to using the copy_file_range() system call. This change homebrews a new allocation API that addresses the shortcomings of the C standard library design. Using these new balloc() and reballoc() functions I managed to reduce memory consumption so much that Cosmpolitan Ar should now use roughly 100x fewer bytes of peak resident memory compared to llvm-ar. Correct behavior with better compatibility has been assured. Binary output is now pretty much bit-identical to llvm-ar, as of this change. This can and should be the living proof we need to show that a better world is possible for software.
49 lines
2.9 KiB
C
49 lines
2.9 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/elf/def.h"
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#include "libc/elf/elf.h"
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#include "libc/elf/scalar.h"
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#include "libc/stdckdint.h"
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/**
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* Returns pointer to ELF section file content.
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*
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* This function computes `elf + sh_offset` with safety checks.
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*
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* @param elf points to the start of the executable image data
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* @param mapsize is the number of bytes of `elf` we can access
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* @param shdr is from GetElfSectionHeaderAddress(), or null
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* @return pointer to section data within image, or null if
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* 1. `shdr` was null, or
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* 2. `sh_size` was zero, or
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* 3, `sh_type` was `SHT_NOBITS`, or
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* 4. content wasn't contained within `[elf,elf+mapsize)`, or
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* 5. an arithmetic overflow occurred
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*/
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void *GetElfSectionAddress(const Elf64_Ehdr *elf, // validated
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size_t mapsize, // validated
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const Elf64_Shdr *shdr) { // foreign
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Elf64_Off last;
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if (!shdr) return 0;
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if (shdr->sh_size <= 0) return 0;
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if (shdr->sh_type == SHT_NOBITS) return 0;
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if (ckd_add(&last, shdr->sh_offset, shdr->sh_size)) return 0;
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if (last > mapsize) return 0;
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return (char *)elf + shdr->sh_offset;
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}
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