kvm tools: Lookup symbol based on RIP for 'kill -3'

To make debugging easier, look up symbol from guest kernel image based on RIP
when user does 'kill -3' to the hypervisor.

Example output looks as follows:

  Code:
  -----
  rip: [<ffffffff812cb3a0>] delay_loop+30 (/home/penberg/linux/arch/x86/lib/delay.c:32)

Cc: Asias He <asias.hejun@gmail.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Prasad Joshi <prasadjoshi124@gmail.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/tools/kvm/Makefile b/tools/kvm/Makefile
index fb839fcb93f310d6882178c458679fabf7e2c921..1aaed24489a547ca6b54458a19340eef0cdc386c 100644 (file)
--- a/tools/kvm/Makefile
+++ b/tools/kvm/Makefile
@@ -24,6 +24,7 @@ OBJS  += main.o
 OBJS   += mmio.o
 OBJS   += pci.o
 OBJS   += rtc.o
+OBJS   += symbol.o
 OBJS   += term.o
 OBJS   += util.o
 OBJS   += virtio/blk.o
@@ -50,6 +51,7 @@ OBJS  += bios/bios.o
 
 LIBS   += -lrt
 LIBS   += -lpthread
+LIBS   += -lbfd
 
 # Additional ARCH settings for x86
 ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ \

diff --git a/tools/kvm/include/kvm/kvm.h b/tools/kvm/include/kvm/kvm.h
index 501c74c347763d747e4d408910015277a52b2515..b310d50b06e39499634b38970e7785a043ec7539 100644 (file)
--- a/tools/kvm/include/kvm/kvm.h
+++ b/tools/kvm/include/kvm/kvm.h
@@ -28,6 +28,8 @@ struct kvm {
        u16                     boot_sp;
 
        struct interrupt_table  interrupt_table;
+
+       const char              *vmlinux;
 };
 
 struct kvm *kvm__init(const char *kvm_dev, unsigned long ram_size);

diff --git a/tools/kvm/include/kvm/symbol.h b/tools/kvm/include/kvm/symbol.h
new file mode 100644 (file)
index 0000000..eaa84ea
--- /dev/null
+++ b/tools/kvm/include/kvm/symbol.h
@@ -0,0 +1,12 @@
+#ifndef KVM__SYMBOL_H
+#define KVM__SYMBOL_H
+
+#include <stddef.h>
+
+struct kvm;
+
+void symbol__init(const char *vmlinux);
+
+char *symbol__lookup(struct kvm *kvm, unsigned long addr, char *sym, size_t size);
+
+#endif /* KVM__SYMBOL_H */

diff --git a/tools/kvm/kvm-cpu.c b/tools/kvm/kvm-cpu.c
index 8a27e029fd1c6f02556cdbdad97e2b57fce28d43..a507fa4ededebd63b1f36c9a1e35cfaa901fa434 100644 (file)
--- a/tools/kvm/kvm-cpu.c
+++ b/tools/kvm/kvm-cpu.c
@@ -1,5 +1,6 @@
 #include "kvm/kvm-cpu.h"
 
+#include "kvm/symbol.h"
 #include "kvm/util.h"
 #include "kvm/kvm.h"
 
@@ -9,6 +10,7 @@
 #include <sys/mman.h>
 #include <signal.h>
 #include <stdlib.h>
+#include <string.h>
 #include <errno.h>
 #include <stdio.h>
 
@@ -282,11 +284,14 @@ void kvm_cpu__show_registers(struct kvm_cpu *vcpu)
        printf("\n");
 }
 
+#define MAX_SYM_LEN            128
+
 void kvm_cpu__show_code(struct kvm_cpu *vcpu)
 {
        unsigned int code_bytes = 64;
        unsigned int code_prologue = code_bytes * 43 / 64;
        unsigned int code_len = code_bytes;
+       char sym[MAX_SYM_LEN];
        unsigned char c;
        unsigned int i;
        u8 *ip;
@@ -302,6 +307,10 @@ void kvm_cpu__show_code(struct kvm_cpu *vcpu)
        printf("\n Code:\n");
        printf(  " -----\n");
 
+       symbol__lookup(vcpu->kvm, vcpu->regs.rip, sym, MAX_SYM_LEN);
+
+       printf(" rip: [<%016lx>] %s\n\n", (unsigned long) vcpu->regs.rip, sym);
+
        for (i = 0; i < code_len; i++, ip++) {
                if (!host_ptr_in_ram(vcpu->kvm, ip))
                        break;

diff --git a/tools/kvm/kvm-run.c b/tools/kvm/kvm-run.c
index 84f05cbbd699141450d8d9605a6332f6c532a2bd..91a194e81b784c4ab7d3a7efd380fd8707c5c3dd 100644 (file)
--- a/tools/kvm/kvm-run.c
+++ b/tools/kvm/kvm-run.c
@@ -26,6 +26,7 @@
 #include <kvm/ioport.h>
 #include <kvm/threadpool.h>
 #include <kvm/barrier.h>
+#include <kvm/symbol.h>
 
 /* header files for gitish interface  */
 #include <kvm/kvm-run.h>
@@ -52,6 +53,7 @@ static u64 ram_size;
 static u8  image_count;
 static const char *kernel_cmdline;
 static const char *kernel_filename;
+static const char *vmlinux_filename;
 static const char *initrd_filename;
 static const char *image_filename[MAX_DISK_IMAGES];
 static const char *console;
@@ -214,17 +216,25 @@ panic_kvm:
 }
 
 static char kernel[PATH_MAX];
-const char *host_kernels[] = {
+
+static const char *host_kernels[] = {
        "/boot/vmlinuz",
        "/boot/bzImage",
        NULL
 };
-const char *default_kernels[] = {
+
+static const char *default_kernels[] = {
        "./bzImage",
        "../../arch/x86/boot/bzImage",
        NULL
 };
 
+static const char *default_vmlinux[] = {
+       "../../../vmlinux",
+       "../../vmlinux",
+       NULL
+};
+
 static void kernel_usage_with_options(void)
 {
        const char **k;
@@ -317,6 +327,23 @@ static const char *find_kernel(void)
        return NULL;
 }
 
+static const char *find_vmlinux(void)
+{
+       const char **vmlinux;
+
+       vmlinux = &default_vmlinux[0];
+       while (*vmlinux) {
+               struct stat st;
+
+               if (stat(*vmlinux, &st) < 0 || !S_ISREG(st.st_mode)) {
+                       vmlinux++;
+                       continue;
+               }
+               return *vmlinux;
+       }
+       return NULL;
+}
+
 static int root_device(char *dev, long *part)
 {
        struct stat st;
@@ -359,13 +386,13 @@ static char *host_image(char *cmd_line, size_t size)
 
 int kvm_cmd_run(int argc, const char **argv, const char *prefix)
 {
+       struct virtio_net_parameters net_params;
        static char real_cmdline[2048];
        unsigned int nr_online_cpus;
-       int max_cpus;
        int exit_code = 0;
-       int i;
-       struct virtio_net_parameters net_params;
+       int max_cpus;
        char *hi;
+       int i;
 
        signal(SIGALRM, handle_sigalrm);
        signal(SIGQUIT, handle_sigquit);
@@ -399,6 +426,8 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
                return EINVAL;
        }
 
+       vmlinux_filename = find_vmlinux();
+
        if (nrcpus < 1 || nrcpus > KVM_NR_CPUS)
                die("Number of CPUs %d is out of [1;%d] range", nrcpus, KVM_NR_CPUS);
 
@@ -433,6 +462,8 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
        if (!script)
                script = DEFAULT_SCRIPT;
 
+       symbol__init(vmlinux_filename);
+
        term_init();
 
        kvm = kvm__init(kvm_dev, ram_size);
@@ -482,6 +513,8 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
                                real_cmdline))
                die("unable to load kernel %s", kernel_filename);
 
+       kvm->vmlinux            = vmlinux_filename;
+
        ioport__setup_legacy();
 
        rtc__init();

diff --git a/tools/kvm/symbol.c b/tools/kvm/symbol.c
new file mode 100644 (file)
index 0000000..56dd346
--- /dev/null
+++ b/tools/kvm/symbol.c
@@ -0,0 +1,98 @@
+#include "kvm/symbol.h"
+
+#include "kvm/kvm.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <bfd.h>
+
+static bfd             *abfd;
+
+void symbol__init(const char *vmlinux)
+{
+       if (!vmlinux)
+               return;
+
+       bfd_init();
+
+       abfd            = bfd_openr(vmlinux, NULL);
+}
+
+static asymbol *lookup(asymbol **symbols, int nr_symbols, const char *symbol_name)
+{
+       int i;
+
+       for (i = 0; i < nr_symbols; i++) {
+               asymbol *symbol = symbols[i];
+
+               if (!strcmp(bfd_asymbol_name(symbol), symbol_name))
+                       return symbol;
+       }
+
+       return NULL;
+}
+
+char *symbol__lookup(struct kvm *kvm, unsigned long addr, char *sym, size_t size)
+{
+       const char *filename;
+       bfd_vma sym_offset;
+       bfd_vma sym_start;
+       asection *section;
+       unsigned int line;
+       const char *func;
+       long symtab_size;
+       asymbol *symbol;
+       asymbol **syms;
+       int nr_syms;
+       char *s;
+
+       if (!abfd)
+               goto not_found;
+
+       if (!bfd_check_format(abfd, bfd_object))
+               goto not_found;
+
+       symtab_size     = bfd_get_symtab_upper_bound(abfd);
+       if (!symtab_size)
+               goto not_found;
+
+       syms            = malloc(symtab_size);
+       if (!syms)
+               goto not_found;
+
+       nr_syms         = bfd_canonicalize_symtab(abfd, syms);
+
+       section         = bfd_get_section_by_name(abfd, ".debug_aranges");
+       if (!section)
+               goto not_found;
+
+       if (!bfd_find_nearest_line(abfd, section, NULL, addr, &filename, &func, &line))
+               goto not_found;
+
+       if (!func)
+               goto not_found;
+
+       symbol          = lookup(syms, nr_syms, func);
+       if (!symbol)
+               goto not_found;
+
+       sym_start       = bfd_asymbol_value(symbol);
+
+       sym_offset      = addr - sym_start;
+
+       snprintf(sym, size, "%s+%llx (%s:%i)", func, (long long) sym_offset, filename, line);
+
+       sym[size - 1] = '\0';
+
+       free(syms);
+
+       return sym;
+
+not_found:
+       s = strncpy(sym, "<unknown>", size);
+
+       sym[size - 1] = '\0';
+
+       return s;
+}