From a95517992a37488c0bc8b629c47c570e580e407d Mon Sep 17 00:00:00 2001 From: Greg Ungerer Date: Mon, 15 Feb 2016 16:36:29 +1000 Subject: [PATCH] m68k: Use conventional function parameters for do_sigreturn 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 Acked-by: Andreas Schwab Signed-off-by: Geert Uytterhoeven --- arch/m68k/kernel/entry.S | 6 ++++++ arch/m68k/kernel/signal.c | 8 ++------ 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S index b54ac7aba850..97cd3ea5f10b 100644 --- a/arch/m68k/kernel/entry.S +++ b/arch/m68k/kernel/entry.S @@ -71,13 +71,19 @@ ENTRY(__sys_vfork) ENTRY(sys_sigreturn) SAVE_SWITCH_STACK + movel %sp,%sp@- | switch_stack pointer + pea %sp@(SWITCH_STACK_SIZE+4) | pt_regs pointer jbsr do_sigreturn + addql #8,%sp RESTORE_SWITCH_STACK rts ENTRY(sys_rt_sigreturn) SAVE_SWITCH_STACK + movel %sp,%sp@- | switch_stack pointer + pea %sp@(SWITCH_STACK_SIZE+4) | pt_regs pointer jbsr do_rt_sigreturn + addql #8,%sp RESTORE_SWITCH_STACK rts diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c index af1c4f330aef..2dcee3a88867 100644 --- a/arch/m68k/kernel/signal.c +++ b/arch/m68k/kernel/signal.c @@ -737,10 +737,8 @@ badframe: return 1; } -asmlinkage int do_sigreturn(unsigned long __unused) +asmlinkage int do_sigreturn(struct pt_regs *regs, struct switch_stack *sw) { - struct switch_stack *sw = (struct switch_stack *) &__unused; - struct pt_regs *regs = (struct pt_regs *) (sw + 1); unsigned long usp = rdusp(); struct sigframe __user *frame = (struct sigframe __user *)(usp - 4); sigset_t set; @@ -764,10 +762,8 @@ badframe: return 0; } -asmlinkage int do_rt_sigreturn(unsigned long __unused) +asmlinkage int do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw) { - struct switch_stack *sw = (struct switch_stack *) &__unused; - struct pt_regs *regs = (struct pt_regs *) (sw + 1); unsigned long usp = rdusp(); struct rt_sigframe __user *frame = (struct rt_sigframe __user *)(usp - 4); sigset_t set; -- 2.20.1