org.handhelds.familiar/packages/uclibc/uclibc-0.9.28/thumb-swi-r7.patch

   1 # This is a work round for a fairly serious GCC compiler bug - when
   2 # the syscall assembler overwrites r7 (required on thumb) the
   3 # compiler fails to protect the register when it is using it as a
   4 # frame pointer.
   5 #
   6 --- uClibc-0.9.28/libc/sysdeps/linux/arm/bits/syscalls.h        2005-09-12 17:51:26.062205918 -0700
   7 +++ uClibc-0.9.28/libc/sysdeps/linux/arm/bits/syscalls.h        2005-09-12 18:16:15.507930828 -0700
   8 @@ -111,6 +111,11 @@
   9       }                                                         \
  10       (int) _sys_result; })
  11  #else
  12 +#if 0
  13 +/* This doesn't work because GCC uses r7 as a frame pointer in
  14 + * some cases and doesn't notice that the _r7 value changes
  15 + * it, resulting in mysterious crashes after the SWI.
  16 + */
  17  #define INTERNAL_SYSCALL(name, err, nr, args...)               \
  18    ({ unsigned int _sys_result;                                 \
  19       {                                                         \
  20 @@ -124,6 +129,28 @@
  21         _sys_result = _a1;                                      \
  22       }                                                         \
  23       (int) _sys_result; })
  24 +#else
  25 +/* So hide the use of r7 from the compiler, this would be a lot
  26 + * easier but for the fact that the syscalls can exceed 255.
  27 + * For the moment the LOAD_ARG_7 is sacrificed.
  28 + */
  29 +#define INTERNAL_SYSCALL(name, err, nr, args...)               \
  30 +  ({ unsigned int _sys_result;                                 \
  31 +     {                                                         \
  32 +       register int _a1 asm ("a1");                            \
  33 +       LOAD_ARGS_##nr (args)                                   \
  34 +       register int _v3 asm ("v3") = (int) (SYS_ify(name));    \
  35 +       asm volatile ("push     {r7}\n"                         \
  36 +                    "\tmov     r7, v3\n"                       \
  37 +                    "\tswi     0       @ syscall " #name "\n"  \
  38 +                    "\tpop     {r7}"                           \
  39 +                    : "=r" (_a1)                               \
  40 +                    : "r" (_v3) ASM_ARGS_##nr                  \
  41 +                    : "memory");                               \
  42 +       _sys_result = _a1;                                      \
  43 +     }                                                         \
  44 +     (int) _sys_result; })
  45 +#endif
  46  #endif
  47
  48  #undef INTERNAL_SYSCALL_ERROR_P