galak at kernel.crashing.org
Fri Apr 17 23:59:17 EST 2009
On Apr 17, 2009, at 5:41 AM, Benjamin Herrenschmidt wrote:
> On Fri, 2009-04-17 at 20:05 +1000, Paul Mackerras wrote:
>> Benjamin Herrenschmidt writes:
>>> I'm pretty sure they are broken already when running off a 64-bit
>> Maybe not... for 64-bit kernels we have our definition of
>> elf_read_implies_exec in arch/powerpc/include/asm/elf.h, which IIRC
>> sets the read-implies-exec personality thing on old 32-bit binaries.
> Ok, so looking at that more closely, if that had worked, we would
> have had PROT_EXEC, and thus VM_EXEC added to the vma by mmap... which
> apparently didn't occur.
> I think what may be happening is that the binary he's running has the
> PT_GNU_STACK but his libc doesn't ... the kernel will set the
> personality flag based on the binary you are trying to run, not any
> library it uses...
> Kumar, can you try to instrument that a bit and tell us ? What the
> personality flag gets set to and whether mmap sets PROT_EXEC ?
On ppc32 personality is clearly set to 0. On ppc64 the
elf_read_implies_exec does work around the issue (ie I implemented
elf_read_implies_exec as (exec_stk != EXSTACK_DISABLE_X) on ppc32).
However I think its just masking it.
Hear are the PHDRs for the version of init I'm running:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg
PHDR 0x000034 0x10000034 0x10000034 0x000e0 0x000e0 R E 0x4
INTERP 0x000114 0x10000114 0x10000114 0x0000d 0x0000d R 0x1
[Requesting program interpreter: /lib/ld.so.1]
LOAD 0x000000 0x10000000 0x10000000 0x072a0 0x072a0 R E
LOAD 0x0072a0 0x100172a0 0x100172a0 0x00358 0x00988 RW
DYNAMIC 0x0074bc 0x100174bc 0x100174bc 0x000c8 0x000c8 RW 0x4
NOTE 0x000130 0x10000130 0x10000130 0x00020 0x00020 R
I don't think elf_read_implies_exec() is the right solution on ppc32.
As I asked before, can VM_MAYEXEC be of any use to us?
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