arm64: signal: Call arm64_notify_segfault when failing to deliver signal

If we fail to deliver a signal due to taking an unhandled fault on the
stackframe, we can call arm64_notify_segfault to deliver a SEGV can deal
with printing any unhandled signal messages for us, rather than roll our
own printing code.

A side-effect of this change is that we now deliver the frame address
in si_addr along with an si_code of SEGV_{ACC,MAP}ERR, rather than an
si_addr of 0 and an si_code of SI_KERNEL as before.
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/signal.c

@@ -40,6 +40,7 @@
 #include <asm/fpsimd.h>
 #include <asm/ptrace.h>
 #include <asm/signal32.h>
+#include <asm/traps.h>
 #include <asm/vdso.h>
 
 /*
@@ -565,11 +566,7 @@ asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 	return regs->regs[0];
 
 badframe:
-	if (show_unhandled_signals)
-		pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
-				    current->comm, task_pid_nr(current), __func__,
-				    regs->pc, regs->sp);
-	force_sig(SIGSEGV, current);
+	arm64_notify_segfault(regs->sp);
 	return 0;
 }
 

arch/arm64/kernel/signal32.c

@@ -26,6 +26,7 @@
 #include <asm/esr.h>
 #include <asm/fpsimd.h>
 #include <asm/signal32.h>
+#include <asm/traps.h>
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
 
@@ -307,11 +308,7 @@ asmlinkage int compat_sys_sigreturn(struct pt_regs *regs)
 	return regs->regs[0];
 
 badframe:
-	if (show_unhandled_signals)
-		pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
-				    current->comm, task_pid_nr(current), __func__,
-				    regs->pc, regs->compat_sp);
-	force_sig(SIGSEGV, current);
+	arm64_notify_segfault(regs->compat_sp);
 	return 0;
 }
 
@@ -344,11 +341,7 @@ asmlinkage int compat_sys_rt_sigreturn(struct pt_regs *regs)
 	return regs->regs[0];
 
 badframe:
-	if (show_unhandled_signals)
-		pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
-				    current->comm, task_pid_nr(current), __func__,
-				    regs->pc, regs->compat_sp);
-	force_sig(SIGSEGV, current);
+	arm64_notify_segfault(regs->compat_sp);
 	return 0;
 }