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perf core: Add a 'nr' field to perf_event_callchain_context
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We will use it to count how many addresses are in the entry->ip[] array,
excluding PERF_CONTEXT_{KERNEL,USER,etc} entries, so that we can really
return the number of entries specified by the user via the relevant
sysctl, kernel.perf_event_max_contexts, or via the per event
perf_event_attr.sample_max_stack knob.

This way we keep the perf_sample->ip_callchain->nr meaning, that is the
number of entries, be it real addresses or PERF_CONTEXT_ entries, while
honouring the max_stack knobs, i.e. the end result will be max_stack
entries if we have at least that many entries in a given stack trace.

Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
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@acmel
acmel committed May 17, 2016
1 parent cfbcf46 commit 3b1fff0
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Showing 9 changed files with 18 additions and 17 deletions.
2 changes: 1 addition & 1 deletion arch/arm/kernel/perf_callchain.c
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs

tail = (struct frame_tail __user *)regs->ARM_fp - 1;

while ((entry->entry->nr < entry->max_stack) &&
while ((entry->nr < entry->max_stack) &&
tail && !((unsigned long)tail & 0x3))
tail = user_backtrace(tail, entry);
}
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4 changes: 2 additions & 2 deletions arch/arm64/kernel/perf_callchain.c
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Expand Up @@ -122,7 +122,7 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry,

tail = (struct frame_tail __user *)regs->regs[29];

while (entry->entry->nr < entry->max_stack &&
while (entry->nr < entry->max_stack &&
tail && !((unsigned long)tail & 0xf))
tail = user_backtrace(tail, entry);
} else {
Expand All @@ -132,7 +132,7 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry,

tail = (struct compat_frame_tail __user *)regs->compat_fp - 1;

while ((entry->entry->nr < entry->max_stack) &&
while ((entry->nr < entry->max_stack) &&
tail && !((unsigned long)tail & 0x3))
tail = compat_user_backtrace(tail, entry);
#endif
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2 changes: 1 addition & 1 deletion arch/metag/kernel/perf_callchain.c
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Expand Up @@ -65,7 +65,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs

--frame;

while ((entry->entry->nr < entry->max_stack) && frame)
while ((entry->nr < entry->max_stack) && frame)
frame = user_backtrace(frame, entry);
}

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4 changes: 2 additions & 2 deletions arch/mips/kernel/perf_event.c
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Expand Up @@ -35,7 +35,7 @@ static void save_raw_perf_callchain(struct perf_callchain_entry_ctx *entry,
addr = *sp++;
if (__kernel_text_address(addr)) {
perf_callchain_store(entry, addr);
if (entry->entry->nr >= entry->max_stack)
if (entry->nr >= entry->max_stack)
break;
}
}
Expand All @@ -59,7 +59,7 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
}
do {
perf_callchain_store(entry, pc);
if (entry->entry->nr >= entry->max_stack)
if (entry->nr >= entry->max_stack)
break;
pc = unwind_stack(current, &sp, pc, &ra);
} while (pc);
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4 changes: 2 additions & 2 deletions arch/powerpc/perf/callchain.c
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Expand Up @@ -247,7 +247,7 @@ static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
sp = regs->gpr[1];
perf_callchain_store(entry, next_ip);

while (entry->entry->nr < entry->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;
Expand Down Expand Up @@ -453,7 +453,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
sp = regs->gpr[1];
perf_callchain_store(entry, next_ip);

while (entry->entry->nr < entry->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;
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6 changes: 3 additions & 3 deletions arch/sparc/kernel/perf_event.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1756,7 +1756,7 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
}
}
#endif
} while (entry->entry->nr < entry->max_stack);
} while (entry->nr < entry->max_stack);
}

static inline int
Expand Down Expand Up @@ -1790,7 +1790,7 @@ static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
pc = sf.callers_pc;
ufp = (unsigned long)sf.fp + STACK_BIAS;
perf_callchain_store(entry, pc);
} while (entry->entry->nr < entry->max_stack);
} while (entry->nr < entry->max_stack);
}

static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
Expand Down Expand Up @@ -1822,7 +1822,7 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
ufp = (unsigned long)sf.fp;
}
perf_callchain_store(entry, pc);
} while (entry->entry->nr < entry->max_stack);
} while (entry->nr < entry->max_stack);
}

void
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4 changes: 2 additions & 2 deletions arch/x86/events/core.c
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Expand Up @@ -2283,7 +2283,7 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry_ctx *ent

fp = compat_ptr(ss_base + regs->bp);
pagefault_disable();
while (entry->entry->nr < entry->max_stack) {
while (entry->nr < entry->max_stack) {
unsigned long bytes;
frame.next_frame = 0;
frame.return_address = 0;
Expand Down Expand Up @@ -2343,7 +2343,7 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs
return;

pagefault_disable();
while (entry->entry->nr < entry->max_stack) {
while (entry->nr < entry->max_stack) {
unsigned long bytes;
frame.next_frame = NULL;
frame.return_address = 0;
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6 changes: 4 additions & 2 deletions include/linux/perf_event.h
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,7 @@ struct perf_callchain_entry {
struct perf_callchain_entry_ctx {
struct perf_callchain_entry *entry;
u32 max_stack;
u32 nr;
};

struct perf_raw_record {
Expand Down Expand Up @@ -1080,9 +1081,10 @@ extern int sysctl_perf_event_max_stack;

static inline int perf_callchain_store(struct perf_callchain_entry_ctx *ctx, u64 ip)
{
struct perf_callchain_entry *entry = ctx->entry;
if (entry->nr < ctx->max_stack) {
if (ctx->nr < ctx->max_stack) {
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 */
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3 changes: 1 addition & 2 deletions kernel/events/callchain.c
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Original file line number Diff line number Diff line change
Expand Up @@ -196,8 +196,7 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,

ctx.entry = entry;
ctx.max_stack = max_stack;

entry->nr = init_nr;
ctx.nr = entry->nr = init_nr;

if (kernel && !user_mode(regs)) {
if (add_mark)
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