On Wed, Dec 30, 2009 at 06:49:29PM +0000, Jamie Lokier wrote: > Jun Sun wrote: > > (Sent to linux-kernel, but seems nobody cared. Hopefully someone here > > can pick it up) > > I've included uclinux-dev@uclinux.org, because that's where I've seen > most discussion of FLAT format in general. >
Thanks. I should have probably done this at the first place. > > Apparently newer GCC would generate ANCHOR symbols beyond the end of > > data/bss segment on ARM CPUs. As a result, the exiting validity checking > > for relocation symbols in FLAT format will fail for some programs. > > > -#define flat_reloc_valid(reloc, size) ((reloc) <= (size)) > > +#define flat_reloc_valid(reloc, size) ((reloc) <= (size) > > + 0x1000) > > Why 0x1000? Is that an arbitrary number, or does it have a specific > meaning for GCC? > I had a piece of comment in my first patch submission which explains it well. I attached it here. This time around I thought for the simplicity look of code and dropped it. Maybe it should still be there. :) > > This also fixes a cosmetic error in printk. Text segment and data/bss > > segment are allocated from two different areas. It is not meaningful to > > give the diff between them in error reporting messages. > > That part looks fine to me. > > -- Jamie > > ps. Russell, proof that someone is using no-MMU ARM? :-) Yes, ARM on no-MMU CPU is still alive. :) Hopefully you can see some amazing products coming soon that we can all be proud of. Cheers. Jun
diff -Nru linux-2.6.32.2/arch/arm/include/asm/flat.h.orig linux-2.6.32.2/arch/arm/include/asm/flat.h --- linux-2.6.32.2/arch/arm/include/asm/flat.h.orig 2009-12-18 14:27:07.000000000 -0800 +++ linux-2.6.32.2/arch/arm/include/asm/flat.h 2009-12-26 08:22:43.000000000 -0800 @@ -7,7 +7,12 @@ #define flat_argvp_envp_on_stack() 1 #define flat_old_ram_flag(flags) (flags) -#define flat_reloc_valid(reloc, size) ((reloc) <= (size)) +#define flat_reloc_valid(reloc, size) ((reloc) <= (size) + 0x1000) +/* [JSUN] new gcc 4.x generates ANCHOR symbols in order to reduce the size + * of GOT table for PIC code. It is possible the ANCHOR is placed beyond + * the end of data/bss segment up to 4K bytes(12 bits), because ARM allows + * negative 12-bit offset. Thus we allow 0x1000 extra in reloc address range. + */ #define flat_get_addr_from_rp(rp, relval, flags, persistent) get_unaligned(rp) #define flat_put_addr_at_rp(rp, val, relval) put_unaligned(val,rp) #define flat_get_relocate_addr(rel) (rel) diff -Nru linux-2.6.32.2/fs/binfmt_flat.c.orig linux-2.6.32.2/fs/binfmt_flat.c --- linux-2.6.32.2/fs/binfmt_flat.c.orig 2009-12-18 14:27:07.000000000 -0800 +++ linux-2.6.32.2/fs/binfmt_flat.c 2009-12-26 08:22:43.000000000 -0800 @@ -355,7 +355,7 @@ if (!flat_reloc_valid(r, start_brk - start_data + text_len)) { printk("BINFMT_FLAT: reloc outside program 0x%x (0 - 0x%x/0x%x)", - (int) r,(int)(start_brk-start_code),(int)text_len); + (int) r,(int)(start_brk-start_data+text_len),(int)text_len); goto failed; }
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