parisc: Add support for CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN

Allow users to disable kernel warnings for unaligned memory
accesses from kernel via the /proc/sys/kernel/ignore-unaligned-usertrap
procfs entry.
That way users can disable those warnings in case they happen too
often.
Signed-off-by: Helge Deller <deller@gmx.de>

Documentation/admin-guide/sysctl/kernel.rst

@@ -454,7 +454,7 @@ ignore-unaligned-usertrap
 
 On architectures where unaligned accesses cause traps, and where this
 feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_NO_WARN``;
-currently, ``arc`` and ``loongarch``), controls whether all
+currently, ``arc``, ``parisc`` and ``loongarch``), controls whether all
 unaligned traps are logged.
 
 = =============================================================

arch/parisc/Kconfig

@@ -45,6 +45,7 @@ config PARISC
 	select GENERIC_CPU_DEVICES if !SMP
 	select GENERIC_LIB_DEVMEM_IS_ALLOWED
 	select SYSCTL_ARCH_UNALIGN_ALLOW
+	select SYSCTL_ARCH_UNALIGN_NO_WARN
 	select SYSCTL_EXCEPTION_TRACE
 	select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_RELA

arch/parisc/kernel/unaligned.c

@@ -104,6 +104,7 @@
 #define ERR_NOTHANDLED	-1
 
 int unaligned_enabled __read_mostly = 1;
+int no_unaligned_warning __read_mostly;
 
 static int emulate_ldh(struct pt_regs *regs, int toreg)
 {
@@ -399,6 +400,7 @@ void handle_unaligned(struct pt_regs *regs)
 	} else {
 		static DEFINE_RATELIMIT_STATE(kernel_ratelimit, 5 * HZ, 5);
 		if (!(current->thread.flags & PARISC_UAC_NOPRINT) &&
+			!no_unaligned_warning &&
 			__ratelimit(&kernel_ratelimit))
 			pr_warn("Kernel: unaligned access to " RFMT " in %pS "
 					"(iir " RFMT ")\n",