From fef47e2a2e1e75fe50a10f634a80f16808348cc6 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Mon, 5 May 2014 18:07:12 +0200 Subject: parisc: ratelimit userspace segfault printing Ratelimit printing of userspace segfaults and make it runtime configurable via the /proc/sys/debug/exception-trace variable. This should resolve syslog from growing way too fast and thus prevents possible system service attacks. Signed-off-by: Helge Deller Cc: stable@vger.kernel.org # 3.13+ --- arch/parisc/kernel/traps.c | 54 +++++++++++++++++++++------------------------- 1 file changed, 25 insertions(+), 29 deletions(-) (limited to 'arch/parisc/kernel') diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c index 1cd1d0c83b6d..47ee620d15d2 100644 --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include @@ -42,9 +43,6 @@ #include "../math-emu/math-emu.h" /* for handle_fpe() */ -#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */ - /* dumped to the console via printk) */ - #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) DEFINE_SPINLOCK(pa_dbit_lock); #endif @@ -160,6 +158,17 @@ void show_regs(struct pt_regs *regs) } } +static DEFINE_RATELIMIT_STATE(_hppa_rs, + DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST); + +#define parisc_printk_ratelimited(critical, regs, fmt, ...) { \ + if ((critical || show_unhandled_signals) && __ratelimit(&_hppa_rs)) { \ + printk(fmt, ##__VA_ARGS__); \ + show_regs(regs); \ + } \ +} + + static void do_show_stack(struct unwind_frame_info *info) { int i = 1; @@ -229,12 +238,10 @@ void die_if_kernel(char *str, struct pt_regs *regs, long err) if (err == 0) return; /* STFU */ - printk(KERN_CRIT "%s (pid %d): %s (code %ld) at " RFMT "\n", + parisc_printk_ratelimited(1, regs, + KERN_CRIT "%s (pid %d): %s (code %ld) at " RFMT "\n", current->comm, task_pid_nr(current), str, err, regs->iaoq[0]); -#ifdef PRINT_USER_FAULTS - /* XXX for debugging only */ - show_regs(regs); -#endif + return; } @@ -321,14 +328,11 @@ static void handle_break(struct pt_regs *regs) (tt == BUG_TRAP_TYPE_NONE) ? 9 : 0); } -#ifdef PRINT_USER_FAULTS - if (unlikely(iir != GDB_BREAK_INSN)) { - printk(KERN_DEBUG "break %d,%d: pid=%d command='%s'\n", + if (unlikely(iir != GDB_BREAK_INSN)) + parisc_printk_ratelimited(0, regs, + KERN_DEBUG "break %d,%d: pid=%d command='%s'\n", iir & 31, (iir>>13) & ((1<<13)-1), task_pid_nr(current), current->comm); - show_regs(regs); - } -#endif /* send standard GDB signal */ handle_gdb_break(regs, TRAP_BRKPT); @@ -758,11 +762,9 @@ void notrace handle_interruption(int code, struct pt_regs *regs) default: if (user_mode(regs)) { -#ifdef PRINT_USER_FAULTS - printk(KERN_DEBUG "\nhandle_interruption() pid=%d command='%s'\n", - task_pid_nr(current), current->comm); - show_regs(regs); -#endif + parisc_printk_ratelimited(0, regs, KERN_DEBUG + "handle_interruption() pid=%d command='%s'\n", + task_pid_nr(current), current->comm); /* SIGBUS, for lack of a better one. */ si.si_signo = SIGBUS; si.si_code = BUS_OBJERR; @@ -779,16 +781,10 @@ void notrace handle_interruption(int code, struct pt_regs *regs) if (user_mode(regs)) { if ((fault_space >> SPACEID_SHIFT) != (regs->sr[7] >> SPACEID_SHIFT)) { -#ifdef PRINT_USER_FAULTS - if (fault_space == 0) - printk(KERN_DEBUG "User Fault on Kernel Space "); - else - printk(KERN_DEBUG "User Fault (long pointer) (fault %d) ", - code); - printk(KERN_CONT "pid=%d command='%s'\n", - task_pid_nr(current), current->comm); - show_regs(regs); -#endif + parisc_printk_ratelimited(0, regs, KERN_DEBUG + "User fault %d on space 0x%08lx, pid=%d command='%s'\n", + code, fault_space, + task_pid_nr(current), current->comm); si.si_signo = SIGSEGV; si.si_errno = 0; si.si_code = SEGV_MAPERR; -- cgit v1.2.3 From c776cd89fc705fc8b5c2e5ad906bf5d791620fed Mon Sep 17 00:00:00 2001 From: John David Anglin Date: Sun, 11 May 2014 18:40:50 -0400 Subject: parisc: Improve LWS-CAS performance The attached change significantly improves the performance of the LWS-CAS code in syscall.S. This allows a number of packages to build (e.g., zeromq3, gtest and libxs) that previously failed because slow LWS-CAS performance under contention. In particular, interrupts taken while the lock was taken degraded performance significantly. The change does the following: 1) Disables interrupts around the CAS operation, and 2) Changes the loads and stores to use the ordered completer, "o", on PA 2.0. "o" and "ma" with a zero offset are equivalent. The latter is accepted on both PA 1.X and 2.0. The use of ordered loads and stores probably makes no difference on all existing hardware, but it seemed pedantically correct. In particular, the CAS operation must complete before LDCW lock is released. As written before, a processor could reorder the operations. I don't believe the period interrupts are disabled is long enough to significantly increase interrupt latency. For example, the TLB insert code is longer. Worst case is a memory fault in the CAS operation. Signed-off-by: John David Anglin Cc: stable@vger.kernel.org # 3.13+ Signed-off-by: Helge Deller --- arch/parisc/kernel/syscall.S | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'arch/parisc/kernel') diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index a63bb179f79a..838786011037 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -589,10 +589,13 @@ cas_nocontend: # endif /* ENABLE_LWS_DEBUG */ + rsm PSW_SM_I, %r0 /* Disable interrupts */ + /* COW breaks can cause contention on UP systems */ LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */ cas_wouldblock: ldo 2(%r0), %r28 /* 2nd case */ + ssm PSW_SM_I, %r0 b lws_exit /* Contended... */ ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ @@ -619,15 +622,17 @@ cas_action: stw %r1, 4(%sr2,%r20) #endif /* The load and store could fail */ -1: ldw 0(%sr3,%r26), %r28 +1: ldw,ma 0(%sr3,%r26), %r28 sub,<> %r28, %r25, %r0 -2: stw %r24, 0(%sr3,%r26) +2: stw,ma %r24, 0(%sr3,%r26) /* Free lock */ - stw %r20, 0(%sr2,%r20) + stw,ma %r20, 0(%sr2,%r20) #if ENABLE_LWS_DEBUG /* Clear thread register indicator */ stw %r0, 4(%sr2,%r20) #endif + /* Enable interrupts */ + ssm PSW_SM_I, %r0 /* Return to userspace, set no error */ b lws_exit copy %r0, %r21 @@ -639,6 +644,7 @@ cas_action: #if ENABLE_LWS_DEBUG stw %r0, 4(%sr2,%r20) #endif + ssm PSW_SM_I, %r0 b lws_exit ldo -EFAULT(%r0),%r21 /* set errno */ nop -- cgit v1.2.3