From: Eric B Munson Date: Mon, 30 Jun 2008 16:12:13 +0000 (+1000) Subject: powerpc: Keep 3 high personality bytes across exec X-Git-Tag: v2.6.27-rc1~1058^2~70 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a91a03ee31a5c29a934708b7cf37bb8da516d016;p=linux-2.6 powerpc: Keep 3 high personality bytes across exec Currently when a 32 bit process is exec'd on a powerpc 64 bit host the value in the top three bytes of the personality is clobbered. patch adds a check in the SET_PERSONALITY macro that will carry all the values in the top three bytes across the exec. These three bytes currently carry flags to disable address randomisation, limit the address space, force zeroing of an mmapped page, etc. Should an application set any of these bits they will be maintained and honoured on homogeneous environment but discarded and ignored on a heterogeneous environment. So if an application requires all mmapped pages to be initialised to zero and a wrapper is used to setup the personality and exec the target, these flags will remain set on an all 32 or all 64 bit envrionment, but they will be lost in the exec on a mixed 32/64 bit environment. Losing these bits means that the same application would behave differently in different environments. Tested on a POWER5+ machine with 64bit kernel and a mixed 64/32 bit user space. Signed-off-by: Eric B Munson Signed-off-by: Paul Mackerras --- diff --git a/include/asm-powerpc/elf.h b/include/asm-powerpc/elf.h index 746e53d60c..b6a874db80 100644 --- a/include/asm-powerpc/elf.h +++ b/include/asm-powerpc/elf.h @@ -255,7 +255,8 @@ do { \ else \ clear_thread_flag(TIF_ABI_PENDING); \ if (personality(current->personality) != PER_LINUX32) \ - set_personality(PER_LINUX); \ + set_personality(PER_LINUX | \ + (current->personality & (~PER_MASK))); \ } while (0) /* * An executable for which elf_read_implies_exec() returns TRUE will