From 3b0c06226783ffc836217eb34f7eca311b1e63f7 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Wed, 4 Jul 2012 18:16:30 +0100 Subject: ARM: 7442/1: Revert "remove unused restart trampoline" This reverts commit fa18484d0947b976a769d15c83c50617493c81c1. We need the restart trampoline back so that we can revert a related problematic patch 6b5c8045ecc7e726cdaa2a9d9c8e5008050e1252 ("arm: new way of handling ERESTART_RESTARTBLOCK"). Acked-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/kernel/signal.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'arch/arm/kernel/signal.c') diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index fd2392a17ac1..6d3bce5bd7bc 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -27,6 +27,7 @@ */ #define SWI_SYS_SIGRETURN (0xef000000|(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)) #define SWI_SYS_RT_SIGRETURN (0xef000000|(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)) +#define SWI_SYS_RESTART (0xef000000|__NR_restart_syscall|__NR_OABI_SYSCALL_BASE) /* * With EABI, the syscall number has to be loaded into r7. @@ -46,6 +47,18 @@ const unsigned long sigreturn_codes[7] = { MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN, }; +/* + * Either we support OABI only, or we have EABI with the OABI + * compat layer enabled. In the later case we don't know if + * user space is EABI or not, and if not we must not clobber r7. + * Always using the OABI syscall solves that issue and works for + * all those cases. + */ +const unsigned long syscall_restart_code[2] = { + SWI_SYS_RESTART, /* swi __NR_restart_syscall */ + 0xe49df004, /* ldr pc, [sp], #4 */ +}; + /* * atomically swap in the new signal mask, and wait for a signal. */ -- cgit v1.2.3 From 433e2f307beff8adba241646ce9108544e0c5a03 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Wed, 4 Jul 2012 18:17:16 +0100 Subject: ARM: 7443/1: Revert "new way of handling ERESTART_RESTARTBLOCK" This reverts commit 6b5c8045ecc7e726cdaa2a9d9c8e5008050e1252. Conflicts: arch/arm/kernel/ptrace.c The new syscall restarting code can lead to problems if we take an interrupt in userspace just before restarting the svc instruction. If a signal is delivered when returning from the interrupt, the TIF_SYSCALL_RESTARTSYS will remain set and cause any syscalls executed from the signal handler to be treated as a restart of the previously interrupted system call. This includes the final sigreturn call, meaning that we may fail to exit from the signal context. Furthermore, if a system call made from the signal handler requires a restart via the restart_block, it is possible to clear the thread flag and fail to restart the originally interrupted system call. The right solution to this problem is to perform the restarting in the kernel, avoiding the possibility of handling a further signal before the restart is complete. Since we're almost at -rc6, let's revert the new method for now and aim for in-kernel restarting at a later date. Acked-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/kernel/signal.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) (limited to 'arch/arm/kernel/signal.c') diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index 6d3bce5bd7bc..536c5d6b340b 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -605,10 +605,12 @@ static void do_signal(struct pt_regs *regs, int syscall) case -ERESTARTNOHAND: case -ERESTARTSYS: case -ERESTARTNOINTR: - case -ERESTART_RESTARTBLOCK: regs->ARM_r0 = regs->ARM_ORIG_r0; regs->ARM_pc = restart_addr; break; + case -ERESTART_RESTARTBLOCK: + regs->ARM_r0 = -EINTR; + break; } } @@ -624,14 +626,12 @@ static void do_signal(struct pt_regs *regs, int syscall) * debugger has chosen to restart at a different PC. */ if (regs->ARM_pc == restart_addr) { - if (retval == -ERESTARTNOHAND || - retval == -ERESTART_RESTARTBLOCK + if (retval == -ERESTARTNOHAND || (retval == -ERESTARTSYS && !(ka.sa.sa_flags & SA_RESTART))) { regs->ARM_r0 = -EINTR; regs->ARM_pc = continue_addr; } - clear_thread_flag(TIF_SYSCALL_RESTARTSYS); } handle_signal(signr, &ka, &info, regs); @@ -645,8 +645,29 @@ static void do_signal(struct pt_regs *regs, int syscall) * ignore the restart. */ if (retval == -ERESTART_RESTARTBLOCK - && regs->ARM_pc == restart_addr) - set_thread_flag(TIF_SYSCALL_RESTARTSYS); + && regs->ARM_pc == continue_addr) { + if (thumb_mode(regs)) { + regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE; + regs->ARM_pc -= 2; + } else { +#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT) + regs->ARM_r7 = __NR_restart_syscall; + regs->ARM_pc -= 4; +#else + u32 __user *usp; + + regs->ARM_sp -= 4; + usp = (u32 __user *)regs->ARM_sp; + + if (put_user(regs->ARM_pc, usp) == 0) { + regs->ARM_pc = KERN_RESTART_CODE; + } else { + regs->ARM_sp += 4; + force_sigsegv(0, current); + } +#endif + } + } } restore_saved_sigmask(); -- cgit v1.2.3