Linux VM Integration Cleanup

Remove all instances of functions being reimplemented in the SPL.
When the prototypes are available in the linux headers but the
function address itself is not exported use kallsyms_lookup_name()
to find the address.  The function name itself can them become a
define which calls a function pointer.  This is preferable to
reimplementing the function in the SPL because it ensures we get
the correct version of the function for the running kernel.  This
is actually pretty safe because the prototype is defined in the
headers so we know we are calling the function properly.

This patch also includes a rhel5 kernel patch we exports the needed
symbols so we don't need to use kallsyms_lookup_name().  There are
autoconf checks to detect if the symbol is exported and if so to
use it directly.  We should add patches for stock upstream kernels
as needed if for no other reason than so we can easily track which
additional symbols we needed exported.  Those patches can also be
used by anyone willing to rebuild their kernel, but this should
not be a requirement.  The rhel5 version of the export-symbols
patch has been applied to the chaos kernel.

Additional fixes:
1) Implement vmem_size() function using get_vmalloc_info()
2) SPL_CHECK_SYMBOL_EXPORT macro updated to use $LINUX_OBJ instead
   of $LINUX because Module.symvers is a build product.  When
   $LINUX_OBJ != $LINUX we will not properly detect exported symbols.
3) SPL_LINUX_COMPILE_IFELSE macro updated to add include2 and
   $LINUX/include search paths to allow proper compilation when
   the kernel target build directory is not the source directory.

1 files changed, 57 insertions, 0 deletions

diff --git a/module/spl/spl-proc.c b/module/spl/spl-proc.c
index 90c89ce31..d0ce23194 100644
--- a/module/spl/spl-proc.c
+++ b/module/spl/spl-proc.c
@@ -68,6 +68,7 @@ struct proc_dir_entry *proc_spl_kstat = NULL;
 #define CTL_VERSION		CTL_UNNUMBERED /* Version */
 #define CTL_HOSTID		CTL_UNNUMBERED /* Host id by /usr/bin/hostid */
 #define CTL_HW_SERIAL		CTL_UNNUMBERED /* HW serial number by hostid */
+#define CTL_KALLSYMS		CTL_UNNUMBERED /* kallsyms_lookup_name addr */
 
 #define CTL_DEBUG_SUBSYS	CTL_UNNUMBERED /* Debug subsystem */
 #define CTL_DEBUG_MASK		CTL_UNNUMBERED /* Debug mask */
@@ -123,6 +124,7 @@ enum {
 	CTL_VERSION = 1,		/* Version */
 	CTL_HOSTID,			/* Host id reported by /usr/bin/hostid */
 	CTL_HW_SERIAL,			/* Hardware serial number from hostid */
+	CTL_KALLSYMS,			/* Address of kallsyms_lookup_name */
 
 	CTL_DEBUG_SUBSYS,		/* Debug subsystem */
 	CTL_DEBUG_MASK,			/* Debug mask */
@@ -489,6 +491,51 @@ proc_dohostid(struct ctl_table *table, int write, struct file *filp,
         RETURN(rc);
 }
 
+#ifndef HAVE_KALLSYMS_LOOKUP_NAME
+static int
+proc_dokallsyms_lookup_name(struct ctl_table *table, int write,
+			    struct file *filp, void __user *buffer,
+			    size_t *lenp, loff_t *ppos) {
+        int len, rc = 0;
+        char *end, str[32];
+	ENTRY;
+
+        if (write) {
+		/* This may only be set once at module load time */
+		if (spl_kallsyms_lookup_name_fn)
+			RETURN(-EEXIST);
+
+		/* We can't use proc_doulongvec_minmax() in the write
+		 * case hear because the address while a hex value has no
+		 * leading 0x which confuses the helper function. */
+                rc = proc_copyin_string(str, sizeof(str), buffer, *lenp);
+                if (rc < 0)
+                        RETURN(rc);
+
+                spl_kallsyms_lookup_name_fn =
+			(kallsyms_lookup_name_t)simple_strtoul(str, &end, 16);
+		if (str == end)
+			RETURN(-EINVAL);
+
+                *ppos += *lenp;
+        } else {
+                len = snprintf(str, sizeof(str), "%lx",
+			       (unsigned long)spl_kallsyms_lookup_name_fn);
+                if (*ppos >= len)
+                        rc = 0;
+                else
+                        rc = proc_copyout_string(buffer,*lenp,str+*ppos,"\n");
+
+                if (rc >= 0) {
+                        *lenp = rc;
+                        *ppos += rc;
+                }
+        }
+
+        RETURN(rc);
+}
+#endif /* HAVE_KALLSYMS_LOOKUP_NAME */
+
 static int
 proc_doavailrmem(struct ctl_table *table, int write, struct file *filp,
                  void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -1018,6 +1065,16 @@ static struct ctl_table spl_table[] = {
                 .mode     = 0444,
                 .proc_handler = &proc_dostring,
         },
+#ifndef HAVE_KALLSYMS_LOOKUP_NAME
+        {
+                .ctl_name = CTL_KALLSYMS,
+                .procname = "kallsyms_lookup_name",
+                .data     = &spl_kallsyms_lookup_name_fn,
+                .maxlen   = sizeof(unsigned long),
+                .mode     = 0644,
+                .proc_handler = &proc_dokallsyms_lookup_name,
+        },
+#endif
 	{
 		.ctl_name = CTL_SPL_DEBUG,
 		.procname = "debug",