Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf updates from Ingo Molnar:
 "Mostly tooling and PMU driver fixes, but also a number of late updates
  such as the reworking of the call-chain size limiting logic to make
  call-graph recording more robust, plus tooling side changes for the
  new 'backwards ring-buffer' extension to the perf ring-buffer"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits)
  perf record: Read from backward ring buffer
  perf record: Rename variable to make code clear
  perf record: Prevent reading invalid data in record__mmap_read
  perf evlist: Add API to pause/resume
  perf trace: Use the ptr->name beautifier as default for "filename" args
  perf trace: Use the fd->name beautifier as default for "fd" args
  perf report: Add srcline_from/to branch sort keys
  perf evsel: Record fd into perf_mmap
  perf evsel: Add overwrite attribute and check write_backward
  perf tools: Set buildid dir under symfs when --symfs is provided
  perf trace: Only auto set call-graph to "dwarf" when syscalls are being traced
  perf annotate: Sort list of recognised instructions
  perf annotate: Fix identification of ARM blt and bls instructions
  perf tools: Fix usage of max_stack sysctl
  perf callchain: Stop validating callchains by the max_stack sysctl
  perf trace: Fix exit_group() formatting
  perf top: Use machine->kptr_restrict_warned
  perf trace: Warn when trying to resolve kernel addresses with kptr_restrict=1
  perf machine: Do not bail out if not managing to read ref reloc symbol
  perf/x86/intel/p4: Trival indentation fix, remove space
  ...

Documentation/sysctl/kernel.txt

@@ -61,6 +61,7 @@ show up in /proc/sys/kernel:
 - perf_cpu_time_max_percent
 - perf_event_paranoid
 - perf_event_max_stack
+- perf_event_max_contexts_per_stack
 - pid_max
 - powersave-nap               [ PPC only ]
 - printk
@@ -668,6 +669,19 @@ The default value is 127.
 
 ==============================================================
 
+perf_event_max_contexts_per_stack:
+
+Controls maximum number of stack frame context entries for
+(attr.sample_type & PERF_SAMPLE_CALLCHAIN) configured events, for
+instance, when using 'perf record -g' or 'perf trace --call-graph fp'.
+
+This can only be done when no events are in use that have callchains
+enabled, otherwise writing to this file will return -EBUSY.
+
+The default value is 8.
+
+==============================================================
+
 pid_max:
 
 PID allocation wrap value.  When the kernel's next PID value

MAINTAINERS

@@ -8881,6 +8881,7 @@ F:	arch/*/kernel/*/perf_event*.c
 F:	arch/*/kernel/*/*/perf_event*.c
 F:	arch/*/include/asm/perf_event.h
 F:	arch/*/kernel/perf_callchain.c
+F:	arch/*/events/*
 F:	tools/perf/
 
 PERSONALITY HANDLING

arch/arc/kernel/perf_event.c

@@ -48,7 +48,7 @@ struct arc_callchain_trace {
 static int callchain_trace(unsigned int addr, void *data)
 {
 	struct arc_callchain_trace *ctrl = data;
-	struct perf_callchain_entry *entry = ctrl->perf_stuff;
+	struct perf_callchain_entry_ctx *entry = ctrl->perf_stuff;
 	perf_callchain_store(entry, addr);
 
 	if (ctrl->depth++ < 3)
@@ -58,7 +58,7 @@ static int callchain_trace(unsigned int addr, void *data)
 }
 
 void
-perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	struct arc_callchain_trace ctrl = {
 		.depth = 0,
@@ -69,7 +69,7 @@ perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
 }
 
 void
-perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	/*
 	 * User stack can't be unwound trivially with kernel dwarf unwinder

arch/arm/kernel/perf_callchain.c

@@ -31,7 +31,7 @@ struct frame_tail {
  */
 static struct frame_tail __user *
 user_backtrace(struct frame_tail __user *tail,
-	       struct perf_callchain_entry *entry)
+	       struct perf_callchain_entry_ctx *entry)
 {
 	struct frame_tail buftail;
 	unsigned long err;
@@ -59,7 +59,7 @@ user_backtrace(struct frame_tail __user *tail,
 }
 
 void
-perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	struct frame_tail __user *tail;
 
@@ -75,7 +75,7 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 
 	tail = (struct frame_tail __user *)regs->ARM_fp - 1;
 
-	while ((entry->nr < sysctl_perf_event_max_stack) &&
+	while ((entry->nr < entry->max_stack) &&
 	       tail && !((unsigned long)tail & 0x3))
 		tail = user_backtrace(tail, entry);
 }
@@ -89,13 +89,13 @@ static int
 callchain_trace(struct stackframe *fr,
 		void *data)
 {
-	struct perf_callchain_entry *entry = data;
+	struct perf_callchain_entry_ctx *entry = data;
 	perf_callchain_store(entry, fr->pc);
 	return 0;
 }
 
 void
-perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	struct stackframe fr;
 

arch/arm64/kernel/perf_callchain.c

@@ -31,7 +31,7 @@ struct frame_tail {
  */
 static struct frame_tail __user *
 user_backtrace(struct frame_tail __user *tail,
-	       struct perf_callchain_entry *entry)
+	       struct perf_callchain_entry_ctx *entry)
 {
 	struct frame_tail buftail;
 	unsigned long err;
@@ -76,7 +76,7 @@ struct compat_frame_tail {
 
 static struct compat_frame_tail __user *
 compat_user_backtrace(struct compat_frame_tail __user *tail,
-		      struct perf_callchain_entry *entry)
+		      struct perf_callchain_entry_ctx *entry)
 {
 	struct compat_frame_tail buftail;
 	unsigned long err;
@@ -106,7 +106,7 @@ compat_user_backtrace(struct compat_frame_tail __user *tail,
 }
 #endif /* CONFIG_COMPAT */
 
-void perf_callchain_user(struct perf_callchain_entry *entry,
+void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 			 struct pt_regs *regs)
 {
 	if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
@@ -122,7 +122,7 @@ void perf_callchain_user(struct perf_callchain_entry *entry,
 
 		tail = (struct frame_tail __user *)regs->regs[29];
 
-		while (entry->nr < sysctl_perf_event_max_stack &&
+		while (entry->nr < entry->max_stack &&
 		       tail && !((unsigned long)tail & 0xf))
 			tail = user_backtrace(tail, entry);
 	} else {
@@ -132,7 +132,7 @@ void perf_callchain_user(struct perf_callchain_entry *entry,
 
 		tail = (struct compat_frame_tail __user *)regs->compat_fp - 1;
 
-		while ((entry->nr < sysctl_perf_event_max_stack) &&
+		while ((entry->nr < entry->max_stack) &&
 			tail && !((unsigned long)tail & 0x3))
 			tail = compat_user_backtrace(tail, entry);
 #endif
@@ -146,12 +146,12 @@ void perf_callchain_user(struct perf_callchain_entry *entry,
  */
 static int callchain_trace(struct stackframe *frame, void *data)
 {
-	struct perf_callchain_entry *entry = data;
+	struct perf_callchain_entry_ctx *entry = data;
 	perf_callchain_store(entry, frame->pc);
 	return 0;
 }
 
-void perf_callchain_kernel(struct perf_callchain_entry *entry,
+void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 			   struct pt_regs *regs)
 {
 	struct stackframe frame;

arch/metag/kernel/perf_callchain.c

@@ -29,7 +29,7 @@ static bool is_valid_call(unsigned long calladdr)
 
 static struct metag_frame __user *
 user_backtrace(struct metag_frame __user *user_frame,
-	       struct perf_callchain_entry *entry)
+	       struct perf_callchain_entry_ctx *entry)
 {
 	struct metag_frame frame;
 	unsigned long calladdr;
@@ -56,7 +56,7 @@ user_backtrace(struct metag_frame __user *user_frame,
 }
 
 void
-perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	unsigned long sp = regs->ctx.AX[0].U0;
 	struct metag_frame __user *frame;
@@ -65,7 +65,7 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 
 	--frame;
 
-	while ((entry->nr < sysctl_perf_event_max_stack) && frame)
+	while ((entry->nr < entry->max_stack) && frame)
 		frame = user_backtrace(frame, entry);
 }
 
@@ -78,13 +78,13 @@ static int
 callchain_trace(struct stackframe *fr,
 		void *data)
 {
-	struct perf_callchain_entry *entry = data;
+	struct perf_callchain_entry_ctx *entry = data;
 	perf_callchain_store(entry, fr->pc);
 	return 0;
 }
 
 void
-perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	struct stackframe fr;
 

arch/mips/kernel/perf_event.c

@@ -25,8 +25,8 @@
  * the user stack callchains, we will add it here.
  */
 
-static void save_raw_perf_callchain(struct perf_callchain_entry *entry,
-	unsigned long reg29)
+static void save_raw_perf_callchain(struct perf_callchain_entry_ctx *entry,
+				    unsigned long reg29)
 {
 	unsigned long *sp = (unsigned long *)reg29;
 	unsigned long addr;
@@ -35,14 +35,14 @@ static void save_raw_perf_callchain(struct perf_callchain_entry *entry,
 		addr = *sp++;
 		if (__kernel_text_address(addr)) {
 			perf_callchain_store(entry, addr);
-			if (entry->nr >= sysctl_perf_event_max_stack)
+			if (entry->nr >= entry->max_stack)
 				break;
 		}
 	}
 }
 
-void perf_callchain_kernel(struct perf_callchain_entry *entry,
-		      struct pt_regs *regs)
+void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
+			   struct pt_regs *regs)
 {
 	unsigned long sp = regs->regs[29];
 #ifdef CONFIG_KALLSYMS
@@ -59,7 +59,7 @@ void perf_callchain_kernel(struct perf_callchain_entry *entry,
 	}
 	do {
 		perf_callchain_store(entry, pc);
-		if (entry->nr >= sysctl_perf_event_max_stack)
+		if (entry->nr >= entry->max_stack)
 			break;
 		pc = unwind_stack(current, &sp, pc, &ra);
 	} while (pc);

arch/powerpc/perf/callchain.c

@@ -47,7 +47,7 @@ static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
 }
 
 void
-perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	unsigned long sp, next_sp;
 	unsigned long next_ip;
@@ -76,7 +76,7 @@ perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
 			next_ip = regs->nip;
 			lr = regs->link;
 			level = 0;
-			perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
+			perf_callchain_store_context(entry, PERF_CONTEXT_KERNEL);
 
 		} else {
 			if (level == 0)
@@ -232,7 +232,7 @@ static int sane_signal_64_frame(unsigned long sp)
 		puc == (unsigned long) &sf->uc;
 }
 
-static void perf_callchain_user_64(struct perf_callchain_entry *entry,
+static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 				   struct pt_regs *regs)
 {
 	unsigned long sp, next_sp;
@@ -247,7 +247,7 @@ static void perf_callchain_user_64(struct perf_callchain_entry *entry,
 	sp = regs->gpr[1];
 	perf_callchain_store(entry, next_ip);
 
-	while (entry->nr < sysctl_perf_event_max_stack) {
+	while (entry->nr < entry->max_stack) {
 		fp = (unsigned long __user *) sp;
 		if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
 			return;
@@ -274,7 +274,7 @@ static void perf_callchain_user_64(struct perf_callchain_entry *entry,
 			    read_user_stack_64(&uregs[PT_R1], &sp))
 				return;
 			level = 0;
-			perf_callchain_store(entry, PERF_CONTEXT_USER);
+			perf_callchain_store_context(entry, PERF_CONTEXT_USER);
 			perf_callchain_store(entry, next_ip);
 			continue;
 		}
@@ -319,7 +319,7 @@ static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 	return rc;
 }
 
-static inline void perf_callchain_user_64(struct perf_callchain_entry *entry,
+static inline void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 					  struct pt_regs *regs)
 {
 }
@@ -439,7 +439,7 @@ static unsigned int __user *signal_frame_32_regs(unsigned int sp,
 	return mctx->mc_gregs;
 }
 
-static void perf_callchain_user_32(struct perf_callchain_entry *entry,
+static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
 				   struct pt_regs *regs)
 {
 	unsigned int sp, next_sp;
@@ -453,7 +453,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry,
 	sp = regs->gpr[1];
 	perf_callchain_store(entry, next_ip);
 
-	while (entry->nr < sysctl_perf_event_max_stack) {
+	while (entry->nr < entry->max_stack) {
 		fp = (unsigned int __user *) (unsigned long) sp;
 		if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
 			return;
@@ -473,7 +473,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry,
 			    read_user_stack_32(&uregs[PT_R1], &sp))
 				return;
 			level = 0;
-			perf_callchain_store(entry, PERF_CONTEXT_USER);
+			perf_callchain_store_context(entry, PERF_CONTEXT_USER);
 			perf_callchain_store(entry, next_ip);
 			continue;
 		}
@@ -487,7 +487,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry,
 }
 
 void
-perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	if (current_is_64bit())
 		perf_callchain_user_64(entry, regs);

arch/s390/kernel/perf_event.c

@@ -224,13 +224,13 @@ arch_initcall(service_level_perf_register);
 
 static int __perf_callchain_kernel(void *data, unsigned long address)
 {
-	struct perf_callchain_entry *entry = data;
+	struct perf_callchain_entry_ctx *entry = data;
 
 	perf_callchain_store(entry, address);
 	return 0;
 }
 
-void perf_callchain_kernel(struct perf_callchain_entry *entry,
+void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 			   struct pt_regs *regs)
 {
 	if (user_mode(regs))

arch/sh/kernel/perf_callchain.c

@@ -21,7 +21,7 @@ static int callchain_stack(void *data, char *name)
 
 static void callchain_address(void *data, unsigned long addr, int reliable)
 {
-	struct perf_callchain_entry *entry = data;
+	struct perf_callchain_entry_ctx *entry = data;
 
 	if (reliable)
 		perf_callchain_store(entry, addr);
@@ -33,7 +33,7 @@ static const struct stacktrace_ops callchain_ops = {
 };
 
 void
-perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	perf_callchain_store(entry, regs->pc);
 

arch/sparc/kernel/perf_event.c

@@ -1711,7 +1711,7 @@ static int __init init_hw_perf_events(void)
 }
 pure_initcall(init_hw_perf_events);
 
-void perf_callchain_kernel(struct perf_callchain_entry *entry,
+void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 			   struct pt_regs *regs)
 {
 	unsigned long ksp, fp;
@@ -1756,7 +1756,7 @@ void perf_callchain_kernel(struct perf_callchain_entry *entry,
 			}
 		}
 #endif
-	} while (entry->nr < sysctl_perf_event_max_stack);
+	} while (entry->nr < entry->max_stack);
 }
 
 static inline int
@@ -1769,7 +1769,7 @@ valid_user_frame(const void __user *fp, unsigned long size)
 	return (__range_not_ok(fp, size, TASK_SIZE) == 0);
 }
 
-static void perf_callchain_user_64(struct perf_callchain_entry *entry,
+static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 				   struct pt_regs *regs)
 {
 	unsigned long ufp;
@@ -1790,10 +1790,10 @@ static void perf_callchain_user_64(struct perf_callchain_entry *entry,
 		pc = sf.callers_pc;
 		ufp = (unsigned long)sf.fp + STACK_BIAS;
 		perf_callchain_store(entry, pc);
-	} while (entry->nr < sysctl_perf_event_max_stack);
+	} while (entry->nr < entry->max_stack);
 }
 
-static void perf_callchain_user_32(struct perf_callchain_entry *entry,
+static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
 				   struct pt_regs *regs)
 {
 	unsigned long ufp;
@@ -1822,11 +1822,11 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry,
 			ufp = (unsigned long)sf.fp;
 		}
 		perf_callchain_store(entry, pc);
-	} while (entry->nr < sysctl_perf_event_max_stack);
+	} while (entry->nr < entry->max_stack);
 }
 
 void
-perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	u64 saved_fault_address = current_thread_info()->fault_address;
 	u8 saved_fault_code = get_thread_fault_code();

arch/tile/kernel/perf_event.c

@@ -941,7 +941,7 @@ arch_initcall(init_hw_perf_events);
 /*
  * Tile specific backtracing code for perf_events.
  */
-static inline void perf_callchain(struct perf_callchain_entry *entry,
+static inline void perf_callchain(struct perf_callchain_entry_ctx *entry,
 		    struct pt_regs *regs)
 {
 	struct KBacktraceIterator kbt;
@@ -992,13 +992,13 @@ static inline void perf_callchain(struct perf_callchain_entry *entry,
 	}
 }
 
-void perf_callchain_user(struct perf_callchain_entry *entry,
+void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 		    struct pt_regs *regs)
 {
 	perf_callchain(entry, regs);
 }
 
-void perf_callchain_kernel(struct perf_callchain_entry *entry,
+void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 		      struct pt_regs *regs)
 {
 	perf_callchain(entry, regs);

arch/x86/events/core.c

@@ -2202,7 +2202,7 @@ static int backtrace_stack(void *data, char *name)
 
 static int backtrace_address(void *data, unsigned long addr, int reliable)
 {
-	struct perf_callchain_entry *entry = data;
+	struct perf_callchain_entry_ctx *entry = data;
 
 	return perf_callchain_store(entry, addr);
 }
@@ -2214,7 +2214,7 @@ static const struct stacktrace_ops backtrace_ops = {
 };
 
 void
-perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
 		/* TODO: We don't support guest os callchain now */
@@ -2268,7 +2268,7 @@ static unsigned long get_segment_base(unsigned int segment)
 #include <asm/compat.h>
 
 static inline int
-perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
+perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *entry)
 {
 	/* 32-bit process in 64-bit kernel. */
 	unsigned long ss_base, cs_base;
@@ -2283,7 +2283,7 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
 
 	fp = compat_ptr(ss_base + regs->bp);
 	pagefault_disable();
-	while (entry->nr < sysctl_perf_event_max_stack) {
+	while (entry->nr < entry->max_stack) {
 		unsigned long bytes;
 		frame.next_frame     = 0;
 		frame.return_address = 0;
@@ -2309,14 +2309,14 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
 }
 #else
 static inline int
-perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
+perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *entry)
 {
     return 0;
 }
 #endif
 
 void
-perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
+perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 {
 	struct stack_frame frame;
 	const void __user *fp;
@@ -2343,7 +2343,7 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 		return;
 
 	pagefault_disable();
-	while (entry->nr < sysctl_perf_event_max_stack) {
+	while (entry->nr < entry->max_stack) {
 		unsigned long bytes;
 		frame.next_frame	     = NULL;
 		frame.return_address = 0;

arch/x86/events/intel/p4.c

@@ -826,7 +826,7 @@ static int p4_hw_config(struct perf_event *event)
 		 * Clear bits we reserve to be managed by kernel itself
 		 * and never allowed from a user space
 		 */
-		 event->attr.config &= P4_CONFIG_MASK;
+		event->attr.config &= P4_CONFIG_MASK;
 
 		rc = p4_validate_raw_event(event);
 		if (rc)

arch/x86/events/intel/uncore.c

@@ -891,7 +891,7 @@ static int uncore_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id
 		return -ENODEV;
 
 	pkg = topology_phys_to_logical_pkg(phys_id);
-	if (WARN_ON_ONCE(pkg < 0))
+	if (pkg < 0)
 		return -EINVAL;
 
 	if (UNCORE_PCI_DEV_TYPE(id->driver_data) == UNCORE_EXTRA_PCI_DEV) {

arch/xtensa/kernel/perf_event.c

@@ -323,23 +323,23 @@ static void xtensa_pmu_read(struct perf_event *event)
 
 static int callchain_trace(struct stackframe *frame, void *data)
 {
-	struct perf_callchain_entry *entry = data;
+	struct perf_callchain_entry_ctx *entry = data;
 
 	perf_callchain_store(entry, frame->pc);
 	return 0;
 }
 
-void perf_callchain_kernel(struct perf_callchain_entry *entry,
+void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 			   struct pt_regs *regs)
 {
-	xtensa_backtrace_kernel(regs, sysctl_perf_event_max_stack,
+	xtensa_backtrace_kernel(regs, entry->max_stack,
 				callchain_trace, NULL, entry);
 }
 
-void perf_callchain_user(struct perf_callchain_entry *entry,
+void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 			 struct pt_regs *regs)
 {
-	xtensa_backtrace_user(regs, sysctl_perf_event_max_stack,
+	xtensa_backtrace_user(regs, entry->max_stack,
 			      callchain_trace, entry);
 }
 

include/linux/perf_event.h

@@ -61,6 +61,14 @@ struct perf_callchain_entry {
 	__u64				ip[0]; /* /proc/sys/kernel/perf_event_max_stack */
 };
 
+struct perf_callchain_entry_ctx {
+	struct perf_callchain_entry *entry;
+	u32			    max_stack;
+	u32			    nr;
+	short			    contexts;
+	bool			    contexts_maxed;
+};
+
 struct perf_raw_record {
 	u32				size;
 	void				*data;
@@ -1061,20 +1069,36 @@ extern void perf_event_fork(struct task_struct *tsk);
 /* Callchains */
 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 void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
+extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *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);
+		   u32 max_stack, bool crosstask, bool add_mark);
 extern int get_callchain_buffers(void);
 extern void put_callchain_buffers(void);
 
 extern int sysctl_perf_event_max_stack;
+extern int sysctl_perf_event_max_contexts_per_stack;
 
-static inline int perf_callchain_store(struct perf_callchain_entry *entry, u64 ip)
+static inline int perf_callchain_store_context(struct perf_callchain_entry_ctx *ctx, u64 ip)
 {
-	if (entry->nr < sysctl_perf_event_max_stack) {
+	if (ctx->contexts < sysctl_perf_event_max_contexts_per_stack) {
+		struct perf_callchain_entry *entry = ctx->entry;
 		entry->ip[entry->nr++] = ip;
+		++ctx->contexts;
+		return 0;
+	} else {
+		ctx->contexts_maxed = true;
+		return -1; /* no more room, stop walking the stack */
+	}
+}
+
+static inline int perf_callchain_store(struct perf_callchain_entry_ctx *ctx, u64 ip)
+{
+	if (ctx->nr < ctx->max_stack && !ctx->contexts_maxed) {
+		struct perf_callchain_entry *entry = ctx->entry;
+		entry->ip[entry->nr++] = ip;
+		++ctx->nr;
 		return 0;
 	} else {
 		return -1; /* no more room, stop walking the stack */

include/uapi/linux/perf_event.h

@@ -862,6 +862,7 @@ enum perf_event_type {
 };
 
 #define PERF_MAX_STACK_DEPTH		127
+#define PERF_MAX_CONTEXTS_PER_STACK	  8
 
 enum perf_callchain_context {
 	PERF_CONTEXT_HV			= (__u64)-32,

kernel/bpf/stackmap.c

@@ -136,7 +136,8 @@ u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
 			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 		return -EINVAL;
 
-	trace = get_perf_callchain(regs, init_nr, kernel, user, false, false);
+	trace = get_perf_callchain(regs, init_nr, kernel, user,
+				   sysctl_perf_event_max_stack, false, false);
 
 	if (unlikely(!trace))
 		/* couldn't fetch the stack trace */

kernel/events/callchain.c

@@ -19,11 +19,13 @@ struct callchain_cpus_entries {
 };
 
 int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
+int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK;
 
 static inline size_t perf_callchain_entry__sizeof(void)
 {
 	return (sizeof(struct perf_callchain_entry) +
-		sizeof(__u64) * sysctl_perf_event_max_stack);
+		sizeof(__u64) * (sysctl_perf_event_max_stack +
+				 sysctl_perf_event_max_contexts_per_stack));
 }
 
 static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
@@ -32,12 +34,12 @@ static DEFINE_MUTEX(callchain_mutex);
 static struct callchain_cpus_entries *callchain_cpus_entries;
 
 
-__weak void perf_callchain_kernel(struct perf_callchain_entry *entry,
+__weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 				  struct pt_regs *regs)
 {
 }
 
-__weak void perf_callchain_user(struct perf_callchain_entry *entry,
+__weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 				struct pt_regs *regs)
 {
 }
@@ -176,14 +178,15 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
 	if (!kernel && !user)
 		return NULL;
 
-	return get_perf_callchain(regs, 0, kernel, user, crosstask, true);
+	return get_perf_callchain(regs, 0, kernel, user, sysctl_perf_event_max_stack, 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)
+		   u32 max_stack, bool crosstask, bool add_mark)
 {
 	struct perf_callchain_entry *entry;
+	struct perf_callchain_entry_ctx ctx;
 	int rctx;
 
 	entry = get_callchain_entry(&rctx);
@@ -193,12 +196,16 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
 	if (!entry)
 		goto exit_put;
 
-	entry->nr = init_nr;
+	ctx.entry     = entry;
+	ctx.max_stack = max_stack;
+	ctx.nr	      = entry->nr = init_nr;
+	ctx.contexts       = 0;
+	ctx.contexts_maxed = false;
 
 	if (kernel && !user_mode(regs)) {
 		if (add_mark)
-			perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
-		perf_callchain_kernel(entry, regs);
+			perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL);
+		perf_callchain_kernel(&ctx, regs);
 	}
 
 	if (user) {
@@ -214,8 +221,8 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
 				goto exit_put;
 
 			if (add_mark)
-				perf_callchain_store(entry, PERF_CONTEXT_USER);
-			perf_callchain_user(entry, regs);
+				perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
+			perf_callchain_user(&ctx, regs);
 		}
 	}
 
@@ -225,10 +232,15 @@ exit_put:
 	return entry;
 }
 
+/*
+ * Used for sysctl_perf_event_max_stack and
+ * sysctl_perf_event_max_contexts_per_stack.
+ */
 int perf_event_max_stack_handler(struct ctl_table *table, int write,
 				 void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	int new_value = sysctl_perf_event_max_stack, ret;
+	int *value = table->data;
+	int new_value = *value, ret;
 	struct ctl_table new_table = *table;
 
 	new_table.data = &new_value;
@@ -240,7 +252,7 @@ int perf_event_max_stack_handler(struct ctl_table *table, int write,
 	if (atomic_read(&nr_callchain_events))
 		ret = -EBUSY;
 	else
-		sysctl_perf_event_max_stack = new_value;
+		*value = new_value;
 
 	mutex_unlock(&callchain_mutex);