| m68knommu: fix user a5 register being overwritten |
| |
| On no-MMU systems the application a5 register can be overwitten with the |
| address of the process data segment when processing application signals. |
| For flat format applications compiled with full absolute relocation this |
| effectively corrupts the a5 register on signal processing - and this very |
| quickly leads to process crash and often takes out the whole system with |
| a panic as well. |
| |
| This has no effect on flat format applications compiled with the more |
| common PIC methods (such as -msep-data). These format applications reserve |
| a5 for the pointer to the data segment anyway - so it doesn't change it. |
| |
| A long time ago the a5 register was used in the code packed into the user |
| stack to enable signal return processing. And so it had to be restored on |
| end of signal cleanup processing back to the original a5 user value. This |
| was historically done by saving away a5 in the sigcontext structure. At |
| some point (a long time back it seems) the a5 restore process was changed |
| and it was hard coded to put the user data segment address directly into a5. |
| Which is ok for the common PIC compiled application case, but breaks the |
| full relocation application code. |
| |
| We no longer use this type of signal handling mechanism and so we don't |
| need to do anything special to save and restore a5 at all now. So remove the |
| code that hard codes a5 to the address of the user data segment. |
| |
| Signed-off-by: Greg Ungerer <gerg@linux-m68k.org> |
| --- |
| arch/m68k/kernel/signal.c | 1 - |
| 1 file changed, 1 deletion(-) |
| |
| diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c |
| index 2dcee3a..9202f82 100644 |
| --- a/arch/m68k/kernel/signal.c |
| +++ b/arch/m68k/kernel/signal.c |
| @@ -213,7 +213,6 @@ static inline int frame_extra_sizes(int f) |
| |
| static inline void adjustformat(struct pt_regs *regs) |
| { |
| - ((struct switch_stack *)regs - 1)->a5 = current->mm->start_data; |
| /* |
| * set format byte to make stack appear modulo 4, which it will |
| * be when doing the rte |
| -- |
| 1.9.1 |
