2 Commits

Author	SHA1	Message	Date
Fangrui Song	ee9a251caf	[ELF] Set DF_1_PIE for -pie ... DF_1_PIE originated from Solaris (https://docs.oracle.com/cd/E36784_01/html/E36857/chapter6-42444.html ). GNU ld since https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=5fe2850dd96483f176858fd75c098313d5b20bc2 sets the flag on non-Solaris platforms. It can help distinguish PIE from ET_DYN. eu-classify from elfutils uses this to recognize PIE (https://sourceware.org/git/?p=elfutils.git;a=commit;h=3f489b5c7c78df6d52f8982f79c36e9a220e8951 ) glibc uses this flag to reject dlopen'ing a PIE (https://sourceware.org/bugzilla/show_bug.cgi?id=24323 ) Reviewed By: psmith Differential Revision: https://reviews.llvm.org/D80872	2020-06-01 10:19:41 -07:00
Fangrui Song	0264950697	[ELF] Add -z separate-loadable-segments to complement separate-code and noseparate-code ... D64906 allows PT_LOAD to have overlapping p_offset ranges. In the default R RX RW RW layout + -z noseparate-code case, we do not tail pad segments when transiting to another segment. This can save at most 3*maxPageSize bytes. a) Before D64906, we tail pad R, RX and the first RW. b) With -z separate-code, we tail pad R and RX, but not the first RW (RELRO). In some cases, b) saves one file page. In some cases, b) wastes one virtual memory page. The waste is a concern on Fuchsia. Because it uses compressed binaries, it doesn't benefit from the saved file page. This patch adds -z separate-loadable-segments to restore the behavior before D64906. It can affect section addresses and can thus be used as a debugging mechanism (see PR43214 and ld.so partition bug in crbug.com/998712). Reviewed By: jakehehrlich, ruiu Differential Revision: https://reviews.llvm.org/D67481 llvm-svn: 372807	2019-09-25 03:39:31 +00:00