hi all,
thanks to all of you for your suggestions... it turns out this
is an ARM-specific issue, and maybe some other platforms as well.
(or maybe just my specific ARM kernel/glibc combo. ;)
it turns out x86 ignores some "modes" for pages in memory. or
maybe ld.so doesn't bother to set them. anyway, the code snippet
below "fixes" the pages i need fixed to become R/W/X.
on *my* ARM, you can't default execute data pages; you can't
write text pages; etc, etc. (my kernel is 2.4.0 with glibc 2.1.2.)
i don't know what other platforms enforce this, but hopefully
this is as educational for those suggesting solutions as it has
been for me. if i had specified i was running on ARM originally,
it may have made things clearer.
thanks again,
josh
// fix permissions on __app_code - we need R/W/X, not just R/X ...
// ARM-specific problem, but this fix should work on ALL platform targets
printf("Fixing TEXT segment permissions for R/W/X....\n");
for (i=0; i<APP_CODE_K*1024/PAGESIZE; i++)
{
code = (ui32*) ((((ui32)__app_code + i*PAGESIZE) - 1) & ~(PAGESIZE-1));
if (mprotect( code, PAGESIZE, PROT_READ|PROT_WRITE|PROT_EXEC) )
{
printf("mprotect() on 0x%08x failed!\nerrno (%d) indicates status: ", code, errno);
switch (errno)
{
case EINVAL: printf("EINVAL: not valid ptr, or not multiple of PAGESIZE (%d)\n", PAGESIZE);
break;
case EFAULT: printf("EFAULT: memory can not be accessed.\n");
break;
case EACCES: printf("EACCES: memory can not be given specified access modes.\n");
break;
case ENOMEM: printf("ENOMEM: internal kernel structures could not be allocated.\n");
break;
default: printf("??????: unknown error result.\n");
}
exit( CLNT_MPROT_FAIL );
}
}
note:
the dummy "nop" function "__app_code()" is APP_CODE_K in size of
KBs of NOPs.
note 2:
i hope the KiB/MiB/whatever standard suggestion is never adopted
and revoked really soon now.
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This archive was generated by hypermail 2b29 : Fri Aug 31 2001 - 21:00:29 EST