Index: share/man/man7/mitigations.7 =================================================================== --- share/man/man7/mitigations.7 +++ share/man/man7/mitigations.7 @@ -50,10 +50,10 @@ Write XOR Execute page protection policy .It .Dv PROT_MAX -".It -"Read-Only Relocation (RELRO) -.\".It -.\"Bind Now +.It +Relocation Read-Only (RELRO) +.It +Bind Now .\".It .\"Stack Smashing Protection (SSP) .\".It @@ -192,8 +192,25 @@ .Xr mprotect call, but may not be made executable. .\" -.\".Ss Read-Only Relocation (RELRO) -.\" +.Ss Relocation Read-Only (RELRO) +Relocation Read-Only (RELRO) is a mitigation tool that makes certain portions +of a program's address space read-only, after relocation processing by +.Xr rtld 1 . +In isolation the RELRO option provides +.Em partial RELRO +support, where the +.Xr elf 5 +Procedure Linkage Table (PLT) Global Offset Table (GOT) remains writable to +support +.Xr rtld 1 +lazy binding. +.Pp +RELRO is is enabled by default. +The +.Xr src.conf 5 +build-time option +.Va WITHOUT_RELRO +may be used to disable it. .Ss BIND_NOW The .Va WITH_BIND_NOW @@ -205,11 +222,12 @@ .Xr rtld 1 will then perform all relocation processing when the process starts, instead of on demand (on the first access to each symbol). +.Pp When enabled in combination with .Dv RELRO (which is enabled by default) this provides -.Qt full -RELRO, the entire GOT (.got and .got.plt) are made read-only at program startup, +.Em full RELRO . +The entire GOT (.got and .got.plt) are made read-only at program startup, preventing attacks on the relocation table. Note that this results in a nonstandard Application Binary Interface (ABI), and it is possible that some applications may not function correctly.