Add support to xenctx for printing stack traces on x86_32 and x86_64.

To support this add xc_translate_foreign_address to libxc. This function
walks page tables and translates virtual addresses using a given domain
and vcpu page table.

Signed-off-by: Ian Campbell <Ian.Campbell@XenSource.com>

1 files changed, 386 insertions, 12 deletions

diff --git a/tools/xentrace/xenctx.c b/tools/xentrace/xenctx.c
index fbfd341cd8..32adccde7e 100644
--- a/tools/xentrace/xenctx.c
+++ b/tools/xentrace/xenctx.c
@@ -20,15 +20,184 @@
 #include <errno.h>
 #include <argp.h>
 #include <signal.h>
+#include <string.h>
+#include <getopt.h>
 
 #include "xenctrl.h"
 
+int xc_handle = 0;
+int domid = 0;
+int frame_ptrs = 0;
+int stack_trace = 0;
+
+#if defined (__i386__)
+#define FMT_SIZE_T		"%08x"
+#define STACK_POINTER(regs)	(regs->esp)
+#define FRAME_POINTER(regs)	(regs->ebp)
+#define INSTR_POINTER(regs)	(regs->eip)
+#define STACK_ROWS		4
+#define STACK_COLS		8
+#elif defined (__x86_64__)
+#define FMT_SIZE_T		"%016lx"
+#define STACK_POINTER(regs)	(regs->rsp)
+#define FRAME_POINTER(regs)	(regs->rbp)
+#define INSTR_POINTER(regs)	(regs->rip)
+#define STACK_ROWS		4
+#define STACK_COLS		4
+#endif
+
+struct symbol {
+    size_t address;
+    char type;
+    char *name;
+    struct symbol *next;
+} *symbol_table = NULL;
+
+size_t kernel_stext, kernel_etext, kernel_sinittext, kernel_einittext;
+
+int is_kernel_text(size_t addr)
+{
+#if defined (__i386__)
+    if (symbol_table == NULL)
+        return (addr > 0xc000000);
+#elif defined (__x86_64__)
+    if (symbol_table == NULL)
+        return (addr > 0xffffffff80000000UL);
+#endif
+
+    if (addr >= kernel_stext &&
+        addr <= kernel_etext)
+        return 1;
+    if (addr >= kernel_sinittext &&
+        addr <= kernel_einittext)
+        return 1;
+    return 0;
+}
+
+void free_symbol(struct symbol *symbol)
+{
+    if (symbol == NULL)
+        return;
+    if (symbol->name)
+        free(symbol->name);
+    free(symbol);
+}
+
+void insert_symbol(struct symbol *symbol)
+{
+    static struct symbol *prev = NULL;
+    struct symbol *s = symbol_table;
+
+    if (s == NULL) {
+        symbol_table = symbol;
+        symbol->next = NULL;
+        return;
+    }
+
+    /* The System.map is usually already sorted... */
+    if (prev
+        && prev->address < symbol->address
+        && (!prev->next || prev->next->address > symbol->address)) {
+        s = prev;
+    } else {
+        /* ... otherwise do crappy/slow search for the correct place */
+        while(s && s->next && s->next->address < symbol->address)
+            s = s->next;
+    }
+
+    symbol->next = s->next;
+    s->next = symbol;
+    prev = symbol;
+}
+
+struct symbol *lookup_symbol(size_t address)
+{
+    struct symbol *s = symbol_table;
+
+    while(s && s->next && s->next->address < address)
+        s = s->next;
+
+    if (s && s->address < address)
+        return s;
+
+    return NULL;
+}
+
+void print_symbol(size_t addr)
+{
+    struct symbol *s;
+
+    if (!is_kernel_text(addr))
+        return;
+
+    s = lookup_symbol(addr);
+
+    if (s==NULL)
+        return;
+
+    if (addr==s->address)
+        printf("%s", s->name);
+    else
+        printf("%s+%#x", s->name, (unsigned int)(addr - s->address));
+}
+
+void read_symbol_table(const char *symtab)
+{
+    char line[256];
+    char *p;
+    struct symbol *symbol;
+    FILE *f;
+
+    f = fopen(symtab, "r");
+    if(f == NULL) {
+        fprintf(stderr, "failed to open symbol table %s\n", symtab);
+        exit(-1);
+    }
+
+    while(!feof(f)) {
+        if(fgets(line,256,f)==NULL)
+            break;
+
+        symbol = malloc(sizeof(*symbol));
+
+        /* need more checks for syntax here... */
+        symbol->address = strtoull(line, &p, 16);
+        p++;
+        symbol->type = *p++;
+        p++;
+
+        /* in the future we should handle the module name
+         * being appended here, this would allow us to use
+         * /proc/kallsyms as our symbol table
+         */
+        if (p[strlen(p)-1] == '\n')
+            p[strlen(p)-1] = '\0';
+        symbol->name = strdup(p);
+
+        insert_symbol(symbol);
+
+        if (strcmp(symbol->name, "_stext") == 0)
+            kernel_stext = symbol->address;
+        else if (strcmp(symbol->name, "_etext") == 0)
+            kernel_etext = symbol->address;
+        else if (strcmp(symbol->name, "_sinittext") == 0)
+            kernel_sinittext = symbol->address;
+        else if (strcmp(symbol->name, "_einittext") == 0)
+            kernel_einittext = symbol->address;
+    }
+
+    fclose(f);
+}
+
 #ifdef __i386__
 void print_ctx(vcpu_guest_context_t *ctx1)
 {
     struct cpu_user_regs *regs = &ctx1->user_regs;
 
-    printf("eip: %08x\t", regs->eip);
+    printf("eip: %08x ", regs->eip);
+    print_symbol(regs->eip);
+    printf("\n");
+
     printf("esp: %08x\n", regs->esp);
 
     printf("eax: %08x\t", regs->eax);
@@ -51,7 +220,9 @@ void print_ctx(vcpu_guest_context_t *ctx1)
 {
     struct cpu_user_regs *regs = &ctx1->user_regs;
 
-    printf("rip: %08lx\t", regs->rip);
+    printf("rip: %08lx ", regs->rip);
+    print_symbol(regs->rip);
+    printf("\n");
     printf("rsp: %08lx\n", regs->rsp);
 
     printf("rax: %08lx\t", regs->rax);
@@ -63,8 +234,8 @@ void print_ctx(vcpu_guest_context_t *ctx1)
     printf("rdi: %08lx\t", regs->rdi);
     printf("rbp: %08lx\n", regs->rbp);
 
-    printf("r8: %08lx\t", regs->r8);
-    printf("r9: %08lx\t", regs->r9);
+    printf(" r8: %08lx\t", regs->r8);
+    printf(" r9: %08lx\t", regs->r9);
     printf("r10: %08lx\t", regs->r10);
     printf("r11: %08lx\n", regs->r11);
 
@@ -81,35 +252,238 @@ void print_ctx(vcpu_guest_context_t *ctx1)
 }
 #endif
 
-void dump_ctx(uint32_t domid, uint32_t vcpu)
+void *map_page(vcpu_guest_context_t *ctx, int vcpu, size_t virt)
+{
+    static unsigned long previous_mfn = 0;
+    static void *mapped = NULL;
+
+    unsigned long mfn = xc_translate_foreign_address(xc_handle, domid, vcpu, virt);
+    unsigned long offset = virt & ~XC_PAGE_MASK;
+
+    if (mapped && mfn == previous_mfn)
+        goto out;
+
+    if (mapped)
+        munmap(mapped, XC_PAGE_SIZE);
+
+    previous_mfn = mfn;
+
+    mapped = xc_map_foreign_range(xc_handle, domid, XC_PAGE_SIZE, PROT_READ, mfn);
+
+    if (mapped == NULL) {
+        fprintf(stderr, "failed to map page.\n");
+        exit(-1);
+    }
+
+ out:
+    return (void *)(mapped + offset);
+}
+
+void print_stack(vcpu_guest_context_t *ctx, int vcpu)
+{
+    struct cpu_user_regs *regs = &ctx->user_regs;
+    size_t stack = STACK_POINTER(regs);
+    size_t stack_limit = (STACK_POINTER(regs) & XC_PAGE_MASK) + XC_PAGE_SIZE;
+    size_t frame;
+    size_t instr;
+    size_t *p;
+    int i;
+
+    printf("\n");
+    printf("Stack:\n");
+    for (i=1; i<STACK_ROWS+1 && stack < stack_limit; i++) {
+        while(stack < stack_limit && stack < STACK_POINTER(regs) + i*STACK_COLS*sizeof(stack)) {
+            p = map_page(ctx, vcpu, stack);
+            printf(" " FMT_SIZE_T, *p);
+            stack += sizeof(stack);
+        }
+        printf("\n");
+    }
+    printf("\n");
+
+    printf("Code:\n");
+    instr = INSTR_POINTER(regs) - 21;
+    for(i=0; i<32; i++) {
+        unsigned char *c = map_page(ctx, vcpu, instr+i);
+        if (instr+i == INSTR_POINTER(regs))
+            printf("<%02x> ", *c);
+        else
+            printf("%02x ", *c);
+    }
+    printf("\n");
+
+    printf("\n");
+
+    if(stack_trace)
+        printf("Stack Trace:\n");
+    else
+        printf("Call Trace:\n");
+    printf("%c [<" FMT_SIZE_T ">] ", stack_trace ? '*' : ' ', INSTR_POINTER(regs));
+
+    print_symbol(INSTR_POINTER(regs));
+    printf(" <--\n");
+    if (frame_ptrs) {
+        stack = STACK_POINTER(regs);
+        frame = FRAME_POINTER(regs);
+        while(frame && stack < stack_limit) {
+            if (stack_trace) {
+                while (stack < frame) {
+                    p = map_page(ctx, vcpu, stack);
+                    printf("|   " FMT_SIZE_T "   ", *p);
+                    printf("\n");
+                    stack += sizeof(*p);
+                }
+            } else {
+                stack = frame;
+            }
+
+            p = map_page(ctx, vcpu, stack);
+            frame = *p;
+            if (stack_trace)
+                printf("|-- " FMT_SIZE_T "\n", *p);
+            stack += sizeof(*p);
+
+            if (frame) {
+                p = map_page(ctx, vcpu, stack);
+                printf("%c [<" FMT_SIZE_T ">] ", stack_trace ? '|' : ' ', *p);
+                print_symbol(*p);
+                printf("\n");
+                stack += sizeof(*p);
+            }
+        }
+    } else {
+        stack = STACK_POINTER(regs);
+        while(stack < stack_limit) {
+            p = map_page(ctx, vcpu, stack);
+            if (is_kernel_text(*p)) {
+                printf("  [<" FMT_SIZE_T ">] ", *p);
+                print_symbol(*p);
+                printf("\n");
+            } else if (stack_trace) {
+                printf("    " FMT_SIZE_T "\n", *p);
+            }
+            stack += sizeof(*p);
+        }
+    }
+}
+
+void dump_ctx(int vcpu)
 {
     int ret;
     vcpu_guest_context_t ctx;
 
-    int xc_handle = xc_interface_open(); /* for accessing control interface */
+    xc_handle = xc_interface_open(); /* for accessing control interface */
+
+    ret = xc_domain_pause(xc_handle, domid);
+    if (ret < 0) {
+        perror("xc_domain_pause");
+        exit(-1);
+    }
 
     ret = xc_domain_get_vcpu_context(xc_handle, domid, vcpu, &ctx);
-    if (ret != 0) {
+    if (ret < 0) {
+        xc_domain_unpause(xc_handle, domid);
         perror("xc_domain_get_vcpu_context");
         exit(-1);
     }
+
     print_ctx(&ctx);
+    if (is_kernel_text(ctx.user_regs.eip))
+        print_stack(&ctx, vcpu);
+
+    ret = xc_domain_unpause(xc_handle, domid);
+    if (ret < 0) {
+        perror("xc_domain_unpause");
+        exit(-1);
+    }
+
     xc_interface_close(xc_handle);
+    if (ret < 0) {
+        perror("xc_interface_close");
+        exit(-1);
+    }
+}
+
+void usage(void)
+{
+    printf("usage:\n\n");
+
+    printf("  xenctx [options] <DOMAIN> [VCPU]\n\n");
+
+    printf("options:\n");
+    printf("  -f, --frame-pointers\n");
+    printf("                    assume the kernel was compiled with\n");
+    printf("                    frame pointers.\n");
+    printf("  -s SYMTAB, --symbol-table=SYMTAB\n");
+    printf("                    read symbol table from SYMTAB.\n");
+    printf("  --stack-trace     print a complete stack trace.\n");
 }
 
 int main(int argc, char **argv)
 {
+    int ch;
+    const char *sopts = "fs:h";
+    const struct option lopts[] = {
+        {"stack-trace", 0, NULL, 'S'},
+        {"symbol-table", 1, NULL, 's'},
+        {"frame-pointers", 0, NULL, 'f'},
+        {"help", 0, NULL, 'h'},
+        {0, 0, 0, 0}
+    };
+    const char *symbol_table = NULL;
+
     int vcpu = 0;
 
-    if (argc < 2) {
-        printf("usage: xenctx <domid> <optional vcpu>\n");
+    while ((ch = getopt_long(argc, argv, sopts, lopts, NULL)) != -1) {
+        switch(ch) {
+        case 'f':
+            frame_ptrs = 1;
+            break;
+        case 's':
+            symbol_table = optarg;
+            break;
+        case 'S':
+            stack_trace = 1;
+            break;
+        case 'h':
+            usage();
+            exit(-1);
+        case '?':
+            fprintf(stderr, "%s --help for more options\n", argv[0]);
+            exit(-1);
+        }
+    }
+
+    argv += optind; argc -= optind;
+
+    if (argc < 1 || argc > 2) {
+        printf("usage: xenctx [options] <domid> <optional vcpu>\n");
         exit(-1);
     }
 
-    if (argc == 3)
-        vcpu = atoi(argv[2]);
+    domid = atoi(argv[0]);
+    if (domid==0) {
+            fprintf(stderr, "cannot trace dom0\n");
+            exit(-1);
+    }
+
+    if (argc == 2)
+        vcpu = atoi(argv[1]);
 
-    dump_ctx(atoi(argv[1]), vcpu);
+    if (symbol_table)
+        read_symbol_table(symbol_table);
+
+    dump_ctx(vcpu);
 
     return 0;
 }
+
+/*
+ * Local variables:
+ * mode: C
+ * c-set-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */