cmd/pprof: don't use local symbolization for remote source

If we are using a remote source (a URL), and the user did not specify
the executable file to use, then don't try to use a local source.
This was misbehaving because the local symbolizer will not fail
if there is any memory map available, but the presence of a memory map
does not ensure that the files and symbols are actually available.

We still need a pprof testsuite.

Fixes #16159.

Change-Id: I0250082a4d5181c7babc7eeec6bc95b2f3bcaec9
Reviewed-on: https://go-review.googlesource.com/24464
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/cmd/pprof/pprof.go b/src/cmd/pprof/pprof.go
index feccd1227b75059a7a031994dee69ce7d415f70e..5ee8a112e0d8e64dd9e19159e46a2255c5f0db5a 100644 (file)
--- a/src/cmd/pprof/pprof.go
+++ b/src/cmd/pprof/pprof.go
@@ -9,6 +9,7 @@ import (
        "debug/gosym"
        "flag"
        "fmt"
+       "net/url"
        "os"
        "regexp"
        "strings"
@@ -50,7 +51,16 @@ func symbolize(mode, source string, p *profile.Profile, obj plugin.ObjTool, ui p
                        ui.PrintErr("expecting -symbolize=[local|remote|none][:force]")
                        fallthrough
                case "", "force":
-                       // Ignore these options, -force is recognized by symbolizer.Symbolize
+                       // -force is recognized by symbolizer.Symbolize.
+                       // If the source is remote, and the mapping file
+                       // does not exist, don't use local symbolization.
+                       if isRemote(source) {
+                               if len(p.Mapping) == 0 {
+                                       local = false
+                               } else if _, err := os.Stat(p.Mapping[0].File); err != nil {
+                                       local = false
+                               }
+                       }
                }
        }
 
@@ -67,6 +77,21 @@ func symbolize(mode, source string, p *profile.Profile, obj plugin.ObjTool, ui p
        return err
 }
 
+// isRemote returns whether source is a URL for a remote source.
+func isRemote(source string) bool {
+       url, err := url.Parse(source)
+       if err != nil {
+               url, err = url.Parse("http://" + source)
+               if err != nil {
+                       return false
+               }
+       }
+       if scheme := strings.ToLower(url.Scheme); scheme == "" || scheme == "file" {
+               return false
+       }
+       return true
+}
+
 // flags implements the driver.FlagPackage interface using the builtin flag package.
 type flags struct {
 }