mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-07-03 17:58:30 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

Rewrite Cosmopolitan Ar

Browse source 
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.
This commit is contained in:
Justine Tunney 2023-07-02 10:19:16 -07:00
parent 197aa0d465
commit 0c630d95b5
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
27 changed files with 916 additions and 341 deletions
Download patch file Download diff file Expand all files Collapse all files

22
libc/elf/getelfsectionaddress.c
View file

@ -16,25 +16,33 @@
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/elf/def.h"
#include "libc/elf/elf.h"
#include "libc/elf/scalar.h"
#include "libc/stdckdint.h"
/**
* Returns pointer to elf section file content.
* Returns pointer to ELF section file content.
*
* This function shouldn't be used on the bss section.
* This function computes `elf + sh_offset` with safety checks.
*
* @param elf points to the start of the executable image
* @param mapsize is the number of bytes past `elf` we can access
* @param shdr is from GetElfSectionHeaderAddress() and null-propagating
* @return pointer to content bytes, or null on error
* @param elf points to the start of the executable image data
* @param mapsize is the number of bytes of `elf` we can access
* @param shdr is from GetElfSectionHeaderAddress(), or null
* @return pointer to section data within image, or null if
* 1. `shdr` was null, or
* 2. `sh_size` was zero, or
* 3, `sh_type` was `SHT_NOBITS`, or
* 4. content wasn't contained within `[elf,elf+mapsize)`, or
* 5. an arithmetic overflow occurred
*/
void *GetElfSectionAddress(const Elf64_Ehdr *elf, // validated
size_t mapsize, // validated
const Elf64_Shdr *shdr) { // foreign
uint64_t last;
Elf64_Off last;
if (!shdr) return 0;
if (shdr->sh_size <= 0) return 0;
if (shdr->sh_type == SHT_NOBITS) return 0;
if (ckd_add(&last, shdr->sh_offset, shdr->sh_size)) return 0;
if (last > mapsize) return 0;
return (char *)elf + shdr->sh_offset;