kvm: Dump state on SIGQUIT

This patch adds state dumping to SIGQUIT signal handler to make debugging
infinite loops easier.  If a kernel gets stuck under KVM, you can press Ctrl-4
and then use 'addr2line' to figure out the exact location where it's stuck from
the reported 'rip':

  ^\[    0.000000] Calibrating delay loop... Registers:
   rip: ffffffff816a0c83   rsp: ffffffff81c01eb8 flags: 0000000000000246
   rax: 00000000ffff8ad0   rbx: ffffffff81d541a0   rcx: 00000000ffffffff
   rdx: 00000000ffff8ad0   rsi: 0000000000000046   rdi: 0000000000002000
   rbp: ffffffff81c01f28   r8:  00000000000003fd   r9:  0000000000000000
   r10: 0000000000000000   r11: 000000000000000d   r12: ffffffff81d56d20
   r13: 0000000000000000   r14: ffffffffffffffff   r15: 0000000000013690
   cr0: 000000008005003b   cr2: 0000000000000000   cr3: 0000000001c08000
   cr4: 00000000000006b0   cr8: 0000000000000000
  Segment registers:
   register  selector  base              limit     type  p dpl db s l g avl
   cs        0010      0000000000000000  ffffffff  0b    1 0   0  1 1 1 0
   ss        0000      0000000000000000  ffffffff  00    0 0   0  0 0 0 0
   ds        0000      0000000000000000  ffffffff  00    0 0   0  0 0 0 0
   es        0000      0000000000000000  ffffffff  00    0 0   0  0 0 0 0
   fs        0000      0000000000000000  ffffffff  00    0 0   0  0 0 0 0
   gs        0000      ffff880002000000  ffffffff  00    0 0   0  0 0 0 0
   tr        0040      ffff880002011bc0  00002087  0b    1 0   0  0 0 0 0
   ldt       0000      0000000000000000  ffffffff  00    0 0   0  0 0 0 0
   gdt                 ffff880002004000  0000007f
   idt                 ffffffff81de9000  00000fff
   [ efer: 0000000000000d01  apic base: 0000000000000000  nmi: enabled ]
  Interrupt bitmap:
   0000000000000000 0000000000000000 0000000000000000 0000000000000000
  Code:
  Stack:
  penberg@tiger:~/vm$ addr2line -e vmlinux
  0xffffffff816a0c83
  /home/penberg/linux/init/calibrate.c:149

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

diff --git a/tools/kvm/main.c b/tools/kvm/main.c
index f74218df562d58a163bd72c8c765493f2801eb2e..617b534a932d5982ca8d6289e13b3e615a44d921 100644 (file)
--- a/tools/kvm/main.c
+++ b/tools/kvm/main.c
@@ -4,6 +4,7 @@
 #include "kvm/util.h"
 
 #include <inttypes.h>
+#include <signal.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
@@ -16,15 +17,29 @@ static void usage(char *argv[])
        exit(1);
 }
 
+static struct kvm *kvm;
+
+static void handle_sigquit(int sig)
+{
+       kvm__show_registers(kvm);
+       kvm__show_code(kvm);
+       kvm__show_page_tables(kvm);
+
+       kvm__delete(kvm);
+
+       exit(1);
+}
+
 int main(int argc, char *argv[])
 {
        const char *kernel_filename = NULL;
        const char *kernel_cmdline = NULL;
        bool single_step = false;
        char real_cmdline[128];
-       struct kvm *kvm;
        int i;
 
+       signal(SIGQUIT, handle_sigquit);
+
        for (i = 1; i < argc; i++) {
                if (!strncmp("--kernel=", argv[i], 9)) {
                        kernel_filename = &argv[i][9];