Per Al Viro's "signals for dummies" https://lkml.org/lkml/2012/12/6/366 there are 3 golden rules for (not) restarting syscalls: " What we need to guarantee is * restarts do not happen on signals caught in interrupts or exceptions * restarts do not happen on signals caught in sigreturn() * restart should happen only once, even if we get through do_signal() many times." ARC Port already handled #1, this patch fixes #2 and #3. We use the additional state in pt_regs->orig_r8 to ckh if restarting has already been done once. Thanks to Al Viro for spotting this. Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> --- arch/arc/include/asm/ptrace.h | 3 +++ arch/arc/kernel/signal.c | 12 ++++++++---- 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h index 1711d56..8bf7ff4 100644 --- a/arch/arc/include/asm/ptrace.h +++ b/arch/arc/include/asm/ptrace.h @@ -135,6 +135,9 @@ struct user_regs_struct { #define in_syscall(regs) (regs->event & orig_r8_IS_SCALL) #define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT) +#define syscall_wont_restart(regs) (regs->event |= orig_r8_IS_SCALL_RESTARTED) +#define syscall_restartable(regs) !(regs->event & orig_r8_IS_SCALL_RESTARTED) + #define current_pt_regs() \ ({ \ /* open-coded current_thread_info() */ \ diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c index 887a383..9a1ea2b 100644 --- a/arch/arc/kernel/signal.c +++ b/arch/arc/kernel/signal.c @@ -131,6 +131,9 @@ SYSCALL_DEFINE0(rt_sigreturn) if (restore_altstack(&sf->uc.uc_stack)) goto badframe; + /* Don't restart from sigreturn */ + syscall_wont_restart(regs); + return regs->r0; badframe: @@ -321,13 +324,13 @@ void do_signal(struct pt_regs *regs) signr = get_signal_to_deliver(&info, &ka, regs, NULL); - /* Are we from a system call? */ - restart_scall = in_syscall(regs); + restart_scall = in_syscall(regs) && syscall_restartable(regs); if (signr > 0) { - if (restart_scall) + if (restart_scall) { arc_restart_syscall(&ka, regs); - + syscall_wont_restart(regs); /* No more restarts */ + } handle_signal(signr, &ka, &info, regs); return; } @@ -342,6 +345,7 @@ void do_signal(struct pt_regs *regs) regs->r8 = __NR_restart_syscall; regs->ret -= 4; } + syscall_wont_restart(regs); /* No more restarts */ } /* If there's no signal to deliver, restore the saved sigmask back */ -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
