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@@ -0,0 +1,100 @@
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+From a95517992a37488c0bc8b629c47c570e580e407d Mon Sep 17 00:00:00 2001
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+From: Greg Ungerer <gerg@uclinux.org>
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+Date: Mon, 15 Feb 2016 16:36:29 +1000
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+Subject: m68k: Use conventional function parameters for do_sigreturn
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+
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+Create conventional stack parameters for the calls to do_sigreturn and
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+do_rt_sigreturn. The current C code for do_sigreturn and do_rt_sigreturn
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+dig into the stack to create local pointers to the saved switch stack
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+and the pt_regs structs.
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+
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+The motivation for this change is a problem with non-MMU targets that
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+have broken signal return paths on newer versions of gcc. It appears as
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+though gcc has determined that the pointers into the saved stack structs,
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+and the saved structs themselves, are function parameters and updates to
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+them will be lost on function return, so they are optimized away. This
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+results in large parts of restore_sigcontext() and mangle_kernel_stack()
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+functions being removed. Of course this results in non-functional code
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+causing kernel oops. This problem has been observed with gcc version
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+5.2 and 5.3, and probably exists in earlier versions as well.
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+
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+Using conventional stack parameter pointers passed to these functions has
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+the advantage of the code here not needing to know the exact details of
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+how the underlying entry handler layed these structs out on the stack.
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+So the rather ugly pointer setup casting and arg referencing can be
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+removed.
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+
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+The resulting code after this change is a few bytes larger (due to the
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+overhead of creating the stack args and their tear down). Not being hot
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+paths I don't think this is too much of a problem here.
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+
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+An alternative solution is to put a barrier() in the do_sigreturn() code,
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+but this doesn't feel quite as clean as this solution.
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+
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+This change has been compile tested on all defconfigs, and run tested on
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+Atari (through aranym), ColdFire with MMU (M5407EVB) and ColdFire with
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+no-MMU (QEMU and M5208EVB).
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+
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+Signed-off-by: Greg Ungerer <gerg@uclinux.org>
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+Acked-by: Andreas Schwab <schwab@linux-m68k.org>
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+Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
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+---
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+ arch/m68k/kernel/entry.S | 6 ++++++
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+ arch/m68k/kernel/signal.c | 8 ++------
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+ 2 files changed, 8 insertions(+), 6 deletions(-)
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+
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+diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
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+index b54ac7a..97cd3ea 100644
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+--- a/arch/m68k/kernel/entry.S
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++++ b/arch/m68k/kernel/entry.S
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+@@ -71,13 +71,19 @@ ENTRY(__sys_vfork)
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+
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+ ENTRY(sys_sigreturn)
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+ SAVE_SWITCH_STACK
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++ movel %sp,%sp@- | switch_stack pointer
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++ pea %sp@(SWITCH_STACK_SIZE+4) | pt_regs pointer
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+ jbsr do_sigreturn
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++ addql #8,%sp
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+ RESTORE_SWITCH_STACK
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+ rts
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+
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+ ENTRY(sys_rt_sigreturn)
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+ SAVE_SWITCH_STACK
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++ movel %sp,%sp@- | switch_stack pointer
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++ pea %sp@(SWITCH_STACK_SIZE+4) | pt_regs pointer
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+ jbsr do_rt_sigreturn
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++ addql #8,%sp
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+ RESTORE_SWITCH_STACK
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+ rts
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+
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+diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c
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+index af1c4f3..2dcee3a 100644
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+--- a/arch/m68k/kernel/signal.c
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++++ b/arch/m68k/kernel/signal.c
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+@@ -737,10 +737,8 @@ badframe:
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+ return 1;
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+ }
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+
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+-asmlinkage int do_sigreturn(unsigned long __unused)
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++asmlinkage int do_sigreturn(struct pt_regs *regs, struct switch_stack *sw)
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+ {
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+- struct switch_stack *sw = (struct switch_stack *) &__unused;
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+- struct pt_regs *regs = (struct pt_regs *) (sw + 1);
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+ unsigned long usp = rdusp();
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+ struct sigframe __user *frame = (struct sigframe __user *)(usp - 4);
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+ sigset_t set;
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+@@ -764,10 +762,8 @@ badframe:
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+ return 0;
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+ }
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+
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+-asmlinkage int do_rt_sigreturn(unsigned long __unused)
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++asmlinkage int do_rt_sigreturn(struct pt_regs *regs, struct switch_stack *sw)
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+ {
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+- struct switch_stack *sw = (struct switch_stack *) &__unused;
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+- struct pt_regs *regs = (struct pt_regs *) (sw + 1);
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+ unsigned long usp = rdusp();
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+ struct rt_sigframe __user *frame = (struct rt_sigframe __user *)(usp - 4);
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+ sigset_t set;
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+--
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+cgit v0.12
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+
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Waldemar Brodkorb