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Re: [libvirt] main: fix some compilation issues on non-linux platforms



On 08/16/2011 02:34 PM, Stefan Berger wrote:
On 08/16/2011 02:14 PM, Eric Blake wrote:
On 08/16/2011 12:07 PM, Stefan Berger wrote:
I split this off and pushed the rest.
If procfs's are different, then maybe we should use #if
PROCFS_PID_EXE_LINK_AVAIL here.

Seems like a reasonable name.

What is needed in this case seems to be that /proc/<pid>/exe is a
symbolic link to the executable. This works in Linux and cygwin. Would
testing via

stat /proc/<pid>/exe | sed -n 's/.*\(symbolic link\).*/\1/p'

be a valid test for this that works on all targeted platforms?

stat(1) is not universal, and while it is on both Linux and Cygwin, it might not be present on some other platform that has a procfs that does what we want. It may be sufficient to just use 'test -h /proc/pid/exe' to see if there is a symlink.

Also, you'd need to wrap the test in a cache variable (to allow overrides if we guessed wrong), as well as to skip the test (and assume the worst or at least make some default guesses based on known $host_os) when cross-compiling, since the existence of procfs on the host machine says nothing about it being on the target machine.

Following the latter couldn't it just be handled during runtime altogether?

    Stefan

Along those lines I propose this patch below:

Signed-off-by: Stefan Berger <stefanb linux vnet ibm com>

---
 src/libvirt_private.syms |    1 +
 src/util/util.c          |   17 +++++++++++++++++
 src/util/util.h          |    2 ++
 src/util/virpidfile.c    |    7 ++++---
 4 files changed, 24 insertions(+), 3 deletions(-)

Index: libvirt-acl/src/util/virpidfile.c
===================================================================
--- libvirt-acl.orig/src/util/virpidfile.c
+++ libvirt-acl/src/util/virpidfile.c
@@ -210,10 +210,11 @@ int virPidFileReadPathIfAlive(const char
         *pid = -1;
         return 0;
     }
-#ifdef __linux__
-    if (virFileLinkPointsTo(procpath, binpath) == 0)
+
+    if (virFileIsLink(procpath) &&
+        virFileLinkPointsTo(procpath, binpath) == 0)
         *pid = -1;
-#endif
+
     VIR_FREE(procpath);

     return 0;
Index: libvirt-acl/src/util/util.c
===================================================================
--- libvirt-acl.orig/src/util/util.c
+++ libvirt-acl/src/util/util.c
@@ -570,6 +570,23 @@ int virFileResolveLink(const char *linkp
     return *resultpath == NULL ? -1 : 0;
 }

+
+/*
+ * Check whether the given file is a link.
+ * Returns 1 in case of the file being a link, 0 in case it is not
+ * a link and the negative errno in all other cases.
+ */
+int virFileIsLink(const char *linkpath)
+{
+    struct stat st;
+
+    if (lstat(linkpath, &st) < 0)
+        return -errno;
+
+    return S_ISLNK(st.st_mode);
+}
+
+
 /*
  * Finds a requested executable file in the PATH env. e.g.:
  * "kvm-img" will return "/usr/bin/kvm-img"
Index: libvirt-acl/src/util/util.h
===================================================================
--- libvirt-acl.orig/src/util/util.h
+++ libvirt-acl/src/util/util.h
@@ -78,6 +78,8 @@ int virFileLinkPointsTo(const char *chec
 int virFileResolveLink(const char *linkpath,
                        char **resultpath) ATTRIBUTE_RETURN_CHECK;

+int virFileIsLink(const char *linkpath) ATTRIBUTE_RETURN_CHECK;
+
 char *virFindFileInPath(const char *file);

 bool virFileExists(const char *file) ATTRIBUTE_NONNULL(1);
Index: libvirt-acl/src/libvirt_private.syms
===================================================================
--- libvirt-acl.orig/src/libvirt_private.syms
+++ libvirt-acl/src/libvirt_private.syms
@@ -1047,6 +1047,7 @@ virFileExists;
 virFileFindMountPoint;
 virFileHasSuffix;
 virFileIsExecutable;
+virFileIsLink;
 virFileLinkPointsTo;
 virFileLock;
 virFileMakePath;


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