Commit a9551799 authored by Greg Ungerer's avatar Greg Ungerer Committed by Geert Uytterhoeven

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: default avatarGreg Ungerer <gerg@uclinux.org>
Acked-by: default avatarAndreas Schwab <schwab@linux-m68k.org>
Signed-off-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
parent a9c9d9ac
......@@ -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
......
......@@ -737,10 +737,8 @@ rt_restore_ucontext(struct pt_regs *regs, struct switch_stack *sw,
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 @@ asmlinkage int do_sigreturn(unsigned long __unused)
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;
......
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