Document /proc/self/exe problems on arm*-linux-elf.

2011-12-13 10:53:26 -08:00
parent 67f7e0089c
commit c56eefc739
1 changed files with 15 additions and 0 deletions
@@ -76,6 +76,21 @@ and previous versions did this by default with no option.  However,
 too much other software erroneously assumes that /proc/self/exe
 always exists.
 On arm*-linux-elf there is no good address at which to retain one
 page of the compressed executable.  Pages below the usual .p_vaddr
 0x8000 (32KiB) are rejected by the kernel.  Using a page above the
 original uncompressed brk(0) would require placing the entire initial
 compressed program above uncompressed brk(0), which would significantly
 increase the running brk(0); but too many programs break if brk(0)
 moves.  Thus on arm*-linux-elf the compressed executable begins
 with 0x8000==.p_vaddr, all pages mapped by execve() that are also
 occupied by decompressed bytes are removed before overwriting, and
 /proc/self/exe becomes a "(deleted)" symlink.  It might be possible
 to preserve /proc/self/exe if the original uncompressed executable
 were created with 0x9000==.p_vaddr (one page higher than the usual
 0x8000) so that the compressed page mapped at 0x8000 would linger.
 [This has not been tested.]
 Linux stores the pathname argument that was specified to execve()
 immediately after the '\0' which terminates the character string of the
 last environment variable [as of execve()].  This is true for at least