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ARM: 7443/1: Revert "new way of handling ERESTART_RESTARTBLOCK"

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This reverts commit 6b5c8045ec.

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 <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon
2012-07-04 18:17:16 +01:00
committed by Russell King
parent 3b0c062267
commit 433e2f307b
3 changed files with 28 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
arch/arm/kernel/ptrace.c
View File

@@ -25,7 +25,6 @@
#include <linux/regset.h>
#include <linux/audit.h>
#include <linux/tracehook.h>
#include <linux/unistd.h>
#include <asm/pgtable.h>
#include <asm/traps.h>
@@ -918,8 +917,6 @@ asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
audit_syscall_entry(AUDIT_ARCH_ARM, scno, regs->ARM_r0,
regs->ARM_r1, regs->ARM_r2, regs->ARM_r3);
if (why == 0 && test_and_clear_thread_flag(TIF_SYSCALL_RESTARTSYS))
scno = __NR_restart_syscall - __NR_SYSCALL_BASE;
if (!test_thread_flag(TIF_SYSCALL_TRACE))
return scno;

33
arch/arm/kernel/signal.c
View File

@@ -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();