Commit 77da0802 authored by Mao Minkai's avatar Mao Minkai Committed by guzitao
Browse files

sw64: fix syscall restart 

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8CCR7



--------------------------------

If syscall has completed successfully but r0 happens to be equal to one
of ERESTART* codes, the syscall restart logic would be triggered
incorrectly. To fix this, use syscall_get_error() to make sure we are
using an errno, not return value.

SW64 has a equivalent of arm bug fixed by commit 653d48b2 ("arm: fix
really nasty sigreturn bug"). If signal gets caught by an interrupt that
hits when we have the right value in r0 (513) and r19 (1), *and* another
signal gets delivered upon sigreturn() or rt_sigreturn() (e.g. included
into the blocked mask for the first signal and posted while the handler
had been running), the syscall restart logic will see regs->orig_r0 not
equal to NO_SYSCALL (we are in a syscall, after all), and r0 and r19
already restored to its original value (513 and 1, which happens to
indicate -ERESTARTNOINTR) and assume that we need to apply the usual
syscall restart logics. To fix this, call
force_successful_syscall_return() in sigreturn() and rt_sigreturn() so
the syscall restart logic will not know we are in a syscall.

Signed-off-by: default avatarMao Minkai <maominkai@wxiat.com>
Reviewed-by: default avatarHe Sheng <hesheng@wxiat.com>
Signed-off-by: default avatarGu Zitao <guzitao@wxiat.com>
parent 54bcfb29

arch/sw_64/kernel/signal.c

+15 −10
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <asm/uprobes.h>

#include <asm/vdso.h>

#include <asm/switch_to.h>

#include <asm/syscall.h>



#include "proto.h"
@@ -119,6 +120,8 @@ SYSCALL_DEFINE1(sigreturn, struct sigcontext __user *, sc) 
	struct pt_regs *regs = current_pt_regs();

	sigset_t set;



	force_successful_syscall_return();



	/* Always make any pending restarted system calls return -EINTR */

	current->restart_block.fn = do_no_restart_syscall;
@@ -150,6 +153,8 @@ SYSCALL_DEFINE1(rt_sigreturn, struct rt_sigframe __user *, frame) 
	struct pt_regs *regs = current_pt_regs();

	sigset_t set;



	force_successful_syscall_return();



	/* Always make any pending restarted system calls return -EINTR */

	current->restart_block.fn = do_no_restart_syscall;
@@ -295,21 +300,21 @@ do_signal(struct pt_regs *regs) 
		single_stepping |= ptrace_cancel_bpt(current);

		/* Whee!  Actually deliver the signal.  */

		if (regs->orig_r0 != NO_SYSCALL) {

			switch (regs->regs[0]) {

			case ERESTARTSYS:

			switch (syscall_get_error(current, regs)) {

			case -ERESTARTSYS:

				if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {

					regs->regs[0] = EINTR;

					break;

				}

				fallthrough;

			case ERESTARTNOINTR:

			case -ERESTARTNOINTR:

				/* reset v0 and a3 and replay syscall */

				regs->regs[0] = regs->orig_r0;

				regs->regs[19] = regs->orig_r19;

				regs->pc -= 4;

				break;

			case ERESTARTNOHAND:

			case ERESTART_RESTARTBLOCK:

			case -ERESTARTNOHAND:

			case -ERESTART_RESTARTBLOCK:

				regs->regs[0] = EINTR;

				break;

			}
@@ -319,16 +324,16 @@ do_signal(struct pt_regs *regs) 
	} else {

		single_stepping |= ptrace_cancel_bpt(current);

		if (regs->orig_r0 != NO_SYSCALL) {

			switch (regs->regs[0]) {

			case ERESTARTSYS:

			case ERESTARTNOINTR:

			case ERESTARTNOHAND:

			switch (syscall_get_error(current, regs)) {

			case -ERESTARTSYS:

			case -ERESTARTNOINTR:

			case -ERESTARTNOHAND:

				/* Reset v0 and a3 and replay syscall.  */

				regs->regs[0] = regs->orig_r0;

				regs->regs[19] = regs->orig_r19;

				regs->pc -= 4;

				break;

			case ERESTART_RESTARTBLOCK:

			case -ERESTART_RESTARTBLOCK:

				/* Set v0 to the restart_syscall and replay */

				regs->regs[0] = __NR_restart_syscall;

				regs->pc -= 4;