Re: [PATCH v3 17/23] xsplice: Print dependency and payloads build_id in the keyhandler.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Feb 17, 2016 at 04:10:12AM -0700, Jan Beulich wrote:
> >>> On 16.02.16 at 21:20, <andrew.cooper3@citrix.com> wrote:
> > On 12/02/16 18:05, Konrad Rzeszutek Wilk wrote:
> >> +static void xsplice_print_build_id(char *id, unsigned int len)
> >> +{
> >> +    unsigned int i;
> >> +
> >> +    if ( !len )
> >> +        return;
> >> +
> >> +    for ( i = 0; i < len; i++ )
> >> +    {
> >> +        uint8_t c = id[i];
> >> +        printk("%02x", c);
> > 
> > What about the already existing %*ph custom format?  If the spaces are a
> > problem we could introduce %*phN from Linux which has no spaces.
> > 
> > The advantage of this is that it is a single call to printk, rather than
> > many, and avoids the ability for a different cpu to interleave in the
> > middle of a line.
> 
> I don't think this ability exists anymore after we've switched to
> per-CPU there. Which isn't to say, though, that I wouldn't also
> like to see this be just a single printk().

Would this work for folks:

commit e1905ecf7034635f2a82cd2bbc4f5ff03ee957b0
Author: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date:   Wed Feb 24 15:06:15 2016 -0500

    xsplice: Print build_id in keyhandler and on bootup.
    
    As it should be an useful debug mechanism.
    
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/xen/common/xsplice.c b/xen/common/xsplice.c
index da26b58..b15a2de 100644
--- a/xen/common/xsplice.c
+++ b/xen/common/xsplice.c
@@ -13,6 +13,7 @@
 #include <xen/smp.h>
 #include <xen/softirq.h>
 #include <xen/spinlock.h>
+#include <xen/version.h>
 #include <xen/vmap.h>
 #include <xen/wait.h>
 #include <xen/xsplice_elf.h>
@@ -1079,10 +1080,33 @@ static const char *state2str(uint32_t state)
     return names[state];
 }
 
+static void xsplice_print_build_id(const char *hdr, const char *id,
+                                   unsigned int len)
+{
+    unsigned int i;
+
+    if ( !len )
+        return;
+
+    /* Each byte is two ASCII characters. */
+    if ( len*2 + 1 > sizeof(keyhandler_scratch) )
+        return;
+
+    memset(keyhandler_scratch, 0, len * 2 + 1);
+    for ( i = 0; i < len; i++ )
+        snprintf(&keyhandler_scratch[i * 2], 3, "%02x", (uint8_t)id[i]);
+
+    printk("%s%s\n", hdr, keyhandler_scratch);
+}
+
 static void xsplice_printall(unsigned char key)
 {
     struct payload *data;
-    unsigned int i;
+    char *binary_id = NULL;
+    unsigned int len = 0, i;
+
+    if ( !xen_build_id(&binary_id, &len) )
+        xsplice_print_build_id("build-id: ", binary_id, len);
 
     spin_lock_recursive(&payload_lock);
 
@@ -1106,8 +1130,14 @@ static void xsplice_printall(unsigned char key)
 
 static int __init xsplice_init(void)
 {
+    char *binary_id = NULL;
+    unsigned int len = 0;
     BUILD_BUG_ON( sizeof(struct xsplice_patch_func) != 64 );
 
+    if ( !xen_build_id(&binary_id, &len) )
+        xsplice_print_build_id("build-id: ", binary_id, len);
+
+    xsplice_print_build_id("Hypervisor build-id: ", binary_id, len);
     register_keyhandler('x', xsplice_printall, "print xsplicing info", 1);
     return 0;
 }
> 
> Jan
>