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>

1 files changed, 98 insertions, 0 deletions

diff --git a/symbol.c b/symbol.c
new file mode 100644
index 00000000..56dd346c
--- /dev/null
+++ b/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;
+}