From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Bambrough To: egcs@cygnus.com Cc: libc-hacker mailing list Subject: Re: Patch to allow ARM dynamic linker to fix up PC24 relocs... Date: Fri, 17 Dec 1999 08:53:00 -0000 Message-id: <385A69A7.30E29A26@netwinder.org> References: <384D63FD.D0F942FC@netwinder.org> <19991207183702.C13790@twiddle.net> X-SW-Source: 1999-12/msg00071.html > >This will only happen during program startup. The code in > >question is not in the Icache yet. > > Yes; the danger is that on a system with a writeback Dcache and/or a store > buffer, the modified data might not get flushed out to main memory before > the Icache fill happens. Seems Phil and Richard are both right. The attached patch adds a cache flush just after the readonly protection is restored to .text. I've done this in generic code, because the cache flush is an extremely expensive operation on the ARM. We don't want to do this after every fixup, and only if we do fixups. The patch as written should only affect the ARM (or anyone else who defines CLEAR_CACHE). For all other targets it will disappear after pre-processing. 1999-12-17 Scott Bambrough * sysdeps/arm/dl-machine.h (CLEAR_CACHE): New macro to force a cache flush. * elf/dl-reloc.c (_dl_relocate_object): Add call to flush cache after .text segment fixups. Scott -- Scott Bambrough - Software Engineer REBEL.COM http://www.rebel.com NetWinder http://www.netwinder.org diff -upr glibc-2.1.2.orig/elf/dl-reloc.c glibc-2.1.2/elf/dl-reloc.c --- glibc-2.1.2.orig/elf/dl-reloc.c Sat Feb 20 09:45:53 1999 +++ glibc-2.1.2/elf/dl-reloc.c Fri Dec 10 10:36:33 1999 @@ -126,6 +126,10 @@ _dl_relocate_object (struct link_map *l, if (__mprotect (mapstart, mapend - mapstart, prot) < 0) _dl_signal_error (errno, l->l_name, "can't restore segment prot after reloc"); + +#ifdef CLEAR_CACHE + CLEAR_CACHE (mapstart, mapend); +#endif } } } diff -upr glibc-2.1.2.orig/sysdeps/arm/dl-machine.h glibc-2.1.2/sysdeps/arm/dl-machine.h --- glibc-2.1.2.orig/sysdeps/arm/dl-machine.h Tue Aug 10 01:13:22 1999 +++ glibc-2.1.2/sysdeps/arm/dl-machine.h Fri Dec 10 10:36:57 1999 @@ -35,6 +35,14 @@ VALID_ELF_ABIVERSION(hdr[EI_ABIVERSION]) \ ) +#define CLEAR_CACHE(BEG,END) \ +{ \ + register unsigned long _beg __asm ("a1") = (unsigned long)(BEG); \ + register unsigned long _end __asm ("a2") = (unsigned long)((END) - (BEG));\ + register unsigned long _flg __asm ("a3") = 0; \ + __asm __volatile ("swi 0x9f0002"); \ +} + /* Return nonzero iff E_MACHINE is compatible with the running host. */ static inline int __attribute__ ((unused)) elf_machine_matches_host (Elf32_Half e_machine)