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a95517992a
Create conventional stack parameters for the calls to do_sigreturn and do_rt_sigreturn. The current C code for do_sigreturn and do_rt_sigreturn dig into the stack to create local pointers to the saved switch stack and the pt_regs structs. The motivation for this change is a problem with non-MMU targets that have broken signal return paths on newer versions of gcc. It appears as though gcc has determined that the pointers into the saved stack structs, and the saved structs themselves, are function parameters and updates to them will be lost on function return, so they are optimized away. This results in large parts of restore_sigcontext() and mangle_kernel_stack() functions being removed. Of course this results in non-functional code causing kernel oops. This problem has been observed with gcc version 5.2 and 5.3, and probably exists in earlier versions as well. Using conventional stack parameter pointers passed to these functions has the advantage of the code here not needing to know the exact details of how the underlying entry handler layed these structs out on the stack. So the rather ugly pointer setup casting and arg referencing can be removed. The resulting code after this change is a few bytes larger (due to the overhead of creating the stack args and their tear down). Not being hot paths I don't think this is too much of a problem here. An alternative solution is to put a barrier() in the do_sigreturn() code, but this doesn't feel quite as clean as this solution. This change has been compile tested on all defconfigs, and run tested on Atari (through aranym), ColdFire with MMU (M5407EVB) and ColdFire with no-MMU (QEMU and M5208EVB). Signed-off-by: Greg Ungerer <gerg@uclinux.org> Acked-by: Andreas Schwab <schwab@linux-m68k.org> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> |
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