[PATCH v8 03/20] xenctx: Add -n (--display-stack-pages) option to output larger stack

[Don Slutz <dslutz@verizon.com>]

Important: This is the stack size (also known as stack limit) to
display not the configured stack size.

Note: use with caution (easy to get garbage).

Below is a pictures of a configured 3 page stack, and where
the SP currently is.  Each box is a page.

                            -n 1    -n 2    -n 3

       +------------------+
       |                  |
       |                  |
       |                  |
       |                  |
SP --> |                  |   *       *       *
       +------------------+   	      |	      |
       |                  |	      |	      |
       |                  |	      |	      |
       |                  |	      |	      |
       |                  |	      |	      |
       |                  |	      *	      |
       +------------------+	      	      |
       |                  |		      |
       |                  |		      |
       |                  |		      |
       |                  |		      |
       |                  |		      *
       +------------------+

Display using "-n 3" since the used stack pages is 3.

At a different time, the SP may be in the 1st page and so "-n 3"
will display garbage.

Signed-off-by: Don Slutz <Don@CloudSwitch.com>
---
v8:
       Reworked comment.
       multiple_pages => nr_stack_pages
       Changed usage output.
       Added range checking of option.


 tools/xentrace/xenctx.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/tools/xentrace/xenctx.c b/tools/xentrace/xenctx.c
index 42a47f3..dd84013 100644
--- a/tools/xentrace/xenctx.c
+++ b/tools/xentrace/xenctx.c
@@ -35,11 +35,14 @@ static struct xenctx {
     int frame_ptrs;
     int stack_trace;
     int disp_all;
+    int nr_stack_pages;
     int all_vcpus;
     int self_paused;
     xc_dominfo_t dominfo;
 } xenctx;
 
+#define DEFAULT_NR_STACK_PAGES 1
+
 #if defined (__i386__) || defined (__x86_64__)
 typedef unsigned long long guest_word_t;
 #define FMT_32B_WORD "%08llx"
@@ -664,6 +667,8 @@ static int print_stack(vcpu_guest_context_any_t *ctx, int vcpu, int width)
 
     stack_limit = ((stack_pointer(ctx) + XC_PAGE_SIZE)
                    & ~((guest_word_t) XC_PAGE_SIZE - 1));
+    if ( xenctx.nr_stack_pages > 1 )
+        stack_limit += (xenctx.nr_stack_pages - 1) * XC_PAGE_SIZE;
     printf("\n");
     printf("Stack:\n");
     for (i=1; i<5 && stack < stack_limit; i++) {
@@ -834,18 +839,24 @@ static void usage(void)
         kernel_start);
     printf("  -a, --all          display more registers\n");
     printf("  -C, --all-vcpus    print info for all vcpus\n");
+    printf("  -n PAGES, --display-stack-pages=PAGES\n");
+    printf("                     Display N pages from the stack pointer. (default %d)\n",
+           DEFAULT_NR_STACK_PAGES);
+    printf("                     Changes stack limit.  Note: use with caution (easy\n");
+    printf("                     to get garbage).\n");
 }
 
 int main(int argc, char **argv)
 {
     int ch;
     int ret;
-    static const char *sopts = "fs:hak:SC";
+    static const char *sopts = "fs:hak:SCn:";
     static const struct option lopts[] = {
         {"stack-trace", 0, NULL, 'S'},
         {"symbol-table", 1, NULL, 's'},
         {"frame-pointers", 0, NULL, 'f'},
         {"kernel-start", 1, NULL, 'k'},
+        {"display-stack-pages", 0, NULL, 'n'},
         {"all", 0, NULL, 'a'},
         {"all-vcpus", 0, NULL, 'C'},
         {"help", 0, NULL, 'h'},
@@ -855,6 +866,8 @@ int main(int argc, char **argv)
 
     int vcpu = 0;
 
+    xenctx.nr_stack_pages = DEFAULT_NR_STACK_PAGES;
+
     while ((ch = getopt_long(argc, argv, sopts, lopts, NULL)) != -1) {
         switch(ch) {
         case 'f':
@@ -869,6 +882,16 @@ int main(int argc, char **argv)
         case 'a':
             xenctx.disp_all = 1;
             break;
+        case 'n':
+            xenctx.nr_stack_pages = strtol(optarg, NULL, 0);
+            if ( xenctx.nr_stack_pages < 1)
+            {
+                fprintf(stderr,
+                        "%s: Unsupported value(%d) for --display-stack-pages '%s'. Needs to be >= 1\n",
+                        argv[0], xenctx.nr_stack_pages, optarg);
+                exit(-1);
+            }
+            break;
         case 'C':
             xenctx.all_vcpus = 1;
             break;
-- 
1.8.4