perf: generalize perf_callchain

. avoid walking the stack when there is no room left in the buffer
. generalize get_perf_callchain() to be called from bpf helper

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 70bbe39..7c247e7 100644 (file)
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -37,7 +37,7 @@ print_context_stack_bp(struct thread_info *tinfo,
 /* Generic stack tracer with callbacks */
 
 struct stacktrace_ops {
-       void (*address)(void *data, unsigned long address, int reliable);
+       int (*address)(void *data, unsigned long address, int reliable);
        /* On negative return stop dumping */
        int (*stack)(void *data, char *name);
        walk_stack_t    walk_stack;

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 1b443db..d276b31 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -2180,11 +2180,11 @@ static int backtrace_stack(void *data, char *name)
        return 0;
 }
 
-static void backtrace_address(void *data, unsigned long addr, int reliable)
+static int backtrace_address(void *data, unsigned long addr, int reliable)
 {
        struct perf_callchain_entry *entry = data;
 
-       perf_callchain_store(entry, addr);
+       return perf_callchain_store(entry, addr);
 }
 
 static const struct stacktrace_ops backtrace_ops = {

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 9c30acf..0d1ff4b 100644 (file)
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -135,7 +135,8 @@ print_context_stack_bp(struct thread_info *tinfo,
                if (!__kernel_text_address(addr))
                        break;
 
-               ops->address(data, addr, 1);
+               if (ops->address(data, addr, 1))
+                       break;
                frame = frame->next_frame;
                ret_addr = &frame->return_address;
                print_ftrace_graph_addr(addr, data, ops, tinfo, graph);
@@ -154,10 +155,11 @@ static int print_trace_stack(void *data, char *name)
 /*
  * Print one address/symbol entries per line.
  */
-static void print_trace_address(void *data, unsigned long addr, int reliable)
+static int print_trace_address(void *data, unsigned long addr, int reliable)
 {
        touch_nmi_watchdog();
        printk_stack_address(addr, reliable, data);
+       return 0;
 }
 
 static const struct stacktrace_ops print_trace_ops = {

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index fdd0c64..9ee98ee 100644 (file)
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -14,30 +14,34 @@ static int save_stack_stack(void *data, char *name)
        return 0;
 }
 
-static void
+static int
 __save_stack_address(void *data, unsigned long addr, bool reliable, bool nosched)
 {
        struct stack_trace *trace = data;
 #ifdef CONFIG_FRAME_POINTER
        if (!reliable)
-               return;
+               return 0;
 #endif
        if (nosched && in_sched_functions(addr))
-               return;
+               return 0;
        if (trace->skip > 0) {
                trace->skip--;
-               return;
+               return 0;
        }
-       if (trace->nr_entries < trace->max_entries)
+       if (trace->nr_entries < trace->max_entries) {
                trace->entries[trace->nr_entries++] = addr;
+               return 0;
+       } else {
+               return -1; /* no more room, stop walking the stack */
+       }
 }
 
-static void save_stack_address(void *data, unsigned long addr, int reliable)
+static int save_stack_address(void *data, unsigned long addr, int reliable)
 {
        return __save_stack_address(data, addr, reliable, false);
 }
 
-static void
+static int
 save_stack_address_nosched(void *data, unsigned long addr, int reliable)
 {
        return __save_stack_address(data, addr, reliable, true);

diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
index 4e664bd..cb31a44 100644 (file)
--- a/arch/x86/oprofile/backtrace.c
+++ b/arch/x86/oprofile/backtrace.c
@@ -23,12 +23,13 @@ static int backtrace_stack(void *data, char *name)
        return 0;
 }
 
-static void backtrace_address(void *data, unsigned long addr, int reliable)
+static int backtrace_address(void *data, unsigned long addr, int reliable)
 {
        unsigned int *depth = data;
 
        if ((*depth)--)
                oprofile_add_trace(addr);
+       return 0;
 }
 
 static struct stacktrace_ops backtrace_ops = {

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index b35a61a..7da3c25 100644 (file)
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -964,11 +964,20 @@ DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
 
 extern void perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs);
 extern void perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs);
+extern struct perf_callchain_entry *
+get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
+                  bool crosstask, bool add_mark);
+extern int get_callchain_buffers(void);
+extern void put_callchain_buffers(void);
 
-static inline void perf_callchain_store(struct perf_callchain_entry *entry, u64 ip)
+static inline int perf_callchain_store(struct perf_callchain_entry *entry, u64 ip)
 {
-       if (entry->nr < PERF_MAX_STACK_DEPTH)
+       if (entry->nr < PERF_MAX_STACK_DEPTH) {
                entry->ip[entry->nr++] = ip;
+               return 0;
+       } else {
+               return -1; /* no more room, stop walking the stack */
+       }
 }
 
 extern int sysctl_perf_event_paranoid;

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 9c41800..343c22f 100644 (file)
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -159,15 +159,24 @@ put_callchain_entry(int rctx)
 struct perf_callchain_entry *
 perf_callchain(struct perf_event *event, struct pt_regs *regs)
 {
-       int rctx;
-       struct perf_callchain_entry *entry;
-
-       int kernel = !event->attr.exclude_callchain_kernel;
-       int user   = !event->attr.exclude_callchain_user;
+       bool kernel = !event->attr.exclude_callchain_kernel;
+       bool user   = !event->attr.exclude_callchain_user;
+       /* Disallow cross-task user callchains. */
+       bool crosstask = event->ctx->task && event->ctx->task != current;
 
        if (!kernel && !user)
                return NULL;
 
+       return get_perf_callchain(regs, 0, kernel, user, crosstask, true);
+}
+
+struct perf_callchain_entry *
+get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
+                  bool crosstask, bool add_mark)
+{
+       struct perf_callchain_entry *entry;
+       int rctx;
+
        entry = get_callchain_entry(&rctx);
        if (rctx == -1)
                return NULL;
@@ -175,10 +184,11 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
        if (!entry)
                goto exit_put;
 
-       entry->nr = 0;
+       entry->nr = init_nr;
 
        if (kernel && !user_mode(regs)) {
-               perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
+               if (add_mark)
+                       perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
                perf_callchain_kernel(entry, regs);
        }
 
@@ -191,13 +201,11 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
                }
 
                if (regs) {
-                       /*
-                        * Disallow cross-task user callchains.
-                        */
-                       if (event->ctx->task && event->ctx->task != current)
+                       if (crosstask)
                                goto exit_put;
 
-                       perf_callchain_store(entry, PERF_CONTEXT_USER);
+                       if (add_mark)
+                               perf_callchain_store(entry, PERF_CONTEXT_USER);
                        perf_callchain_user(entry, regs);
                }
        }

diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 2bbad9c..4199b6d 100644 (file)
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -182,8 +182,6 @@ DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)
 /* Callchain handling */
 extern struct perf_callchain_entry *
 perf_callchain(struct perf_event *event, struct pt_regs *regs);
-extern int get_callchain_buffers(void);
-extern void put_callchain_buffers(void);
 
 static inline int get_recursion_context(int *recursion)
 {