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Commit f01cae4e authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'sparc-perf-stack' 



David Ahern says:

====================
sparc64: perf fixes for userspace stacks

Coming back to the perf userspace callchain problem. As a reminder there are
a series of problems trying to use perf to collect callchains with scheduling
tracepoints, e.g., perf sched record -g -- <cmd>.

The first patch disables pagefaults while walking the user stack. As discussed
a couple of months ago this is the right fix, but I was puzzled as to why
processes were terminating with sigbus (and sometimes sigsegv). I believe the
root of this problem is bad addresses trying to walk the frames using frame
pointers. The bad addresses lead to faults that get handled by do_sparc64_fault
and it aborts the task though I am still puzzled as to why it gets past this
check in do_sparc64_fault:

        if (in_atomic() || !mm)
                goto intr_or_no_mm;

pagefault_disable bumps the preempt_count which should make in_atomic return != 0
(building kernels with preemption set to voluntar, CONFIG_PREEMPT_VOLUNTARY=y).

While this set does not fully solve the problem it does prevent a number of
pain points with the current code, most notably able to lock up the system.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents aefbef10 2d89cd86

arch/sparc/include/asm/uaccess_64.h

+22 −0
Original line number Diff line number Diff line
@@ -49,6 +49,28 @@ do { \ 
	__asm__ __volatile__ ("wr %%g0, %0, %%asi" : : "r" ((val).seg));	\

} while(0)



/*

 * Test whether a block of memory is a valid user space address.

 * Returns 0 if the range is valid, nonzero otherwise.

 */

static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)

{

	if (__builtin_constant_p(size))

		return addr > limit - size;



	addr += size;

	if (addr < size)

		return true;



	return addr > limit;

}



#define __range_not_ok(addr, size, limit)                               \

({                                                                      \

	__chk_user_ptr(addr);                                           \

	__chk_range_not_ok((unsigned long __force)(addr), size, limit); \

})



static inline int __access_ok(const void __user * addr, unsigned long size)

{

	return 1;

arch/sparc/kernel/perf_event.c

+21 −3
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ 


#include <asm/stacktrace.h>

#include <asm/cpudata.h>

#include <asm/uaccess.h>

#include <linux/uaccess.h>

#include <linux/atomic.h>

#include <asm/nmi.h>

#include <asm/pcr.h>
@@ -1741,18 +1741,31 @@ void perf_callchain_kernel(struct perf_callchain_entry *entry, 
	} while (entry->nr < PERF_MAX_STACK_DEPTH);

}



static inline int

valid_user_frame(const void __user *fp, unsigned long size)

{

	/* addresses should be at least 4-byte aligned */

	if (((unsigned long) fp) & 3)

		return 0;



	return (__range_not_ok(fp, size, TASK_SIZE) == 0);

}



static void perf_callchain_user_64(struct perf_callchain_entry *entry,

				   struct pt_regs *regs)

{

	unsigned long ufp;



	ufp = regs->u_regs[UREG_I6] + STACK_BIAS;

	ufp = regs->u_regs[UREG_FP] + STACK_BIAS;

	do {

		struct sparc_stackf __user *usf;

		struct sparc_stackf sf;

		unsigned long pc;



		usf = (struct sparc_stackf __user *)ufp;

		if (!valid_user_frame(usf, sizeof(sf)))

			break;



		if (__copy_from_user_inatomic(&sf, usf, sizeof(sf)))

			break;
@@ -1767,7 +1780,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry, 
{

	unsigned long ufp;



	ufp = regs->u_regs[UREG_I6] & 0xffffffffUL;

	ufp = regs->u_regs[UREG_FP] & 0xffffffffUL;

	do {

		unsigned long pc;
@@ -1803,8 +1816,13 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs) 
		return;



	flushw_user();



	pagefault_disable();



	if (test_thread_flag(TIF_32BIT))

		perf_callchain_user_32(entry, regs);

	else

		perf_callchain_user_64(entry, regs);



	pagefault_enable();

}

arch/sparc/mm/fault_64.c

+3 −2
Original line number Diff line number Diff line
@@ -413,8 +413,9 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs) 
	 * that here.

	 */

	if ((fault_code & FAULT_CODE_ITLB) && !(vma->vm_flags & VM_EXEC)) {

		BUG_ON(address != regs->tpc);

		BUG_ON(regs->tstate & TSTATE_PRIV);

		WARN(address != regs->tpc,

		     "address (%lx) != regs->tpc (%lx)\n", address, regs->tpc);

		WARN_ON(regs->tstate & TSTATE_PRIV);

		goto bad_area;

	}