On Sun, 2010-09-19 at 16:33 +0200, Avi Kivity wrote:
> Override kvm_emulate_insn formatting to use a disassembler to format
> the emulated instruction. If a disassembler (udis86) is not available,
> fall back to showing the instruction bytes in hex.
>
> Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
> ---
>
> Note 1: on top of 'master' with 'trace-cmd-kvm' cherry-picked on top.
Thanks, I merged trace-cmd-kvm into master and applied your patch
(haven't pushed yet).
>
> Note 2: I get output of the form
>
> ... kvm_emulate_insn: 0:fffff800010527b5: mov $0x0, 0xfffe00b0CAN'T FIND FIELD "guest_rip"
>
> which leads me to believe there is a bug in trace_seq_printf when the input
> to %s is "".
I ran this under gdb (nice to do that, where I don't in kernel :-) And
it takes me to kvm_emulate_insn_handler() which does the
trace_seq_printf() fine, but then calls pevent_print_num_field() and
that passes in "guest_rip" where we get the "CAN'T FIND FIELD" error.
In pevent_print_num_field() it searches for "guest_rip" at the top of
the function (pevent_find_field()), but the event kvm_emulate_insn does
not have a "guest_rip" field, then it jumps to the error message.
-- Steve
>
> Makefile | 11 +++++-
> plugin_kvm.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 121 insertions(+), 1 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 5282f94..fe34d1c 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -74,6 +74,14 @@ ifeq ($(shell sh -c "python-config --includes > /dev/null 2>&1 && echo y"), y)
> PYTHON_PY_INSTALL := event-viewer.install tracecmd.install tracecmdgui.install
> endif
>
> +# $(call test-build, snippet, ret) -> ret if snippet compiles
> +# -> empty otherwise
> +test-build = $(if $(shell $(CC) -o /dev/null -c -x c - > /dev/null 2>&1 \
> + <<<'$1' && echo y), $2)
> +
> +# have udis86 disassembler library?
> +udis86-flags := $(call test-build,\#include <udis86.h>,-DHAVE_UDIS86 -ludis86)
> +
> ifeq ("$(origin O)", "command line")
> BUILD_OUTPUT := $(O)
> endif
> @@ -188,6 +196,7 @@ CFLAGS ?= -g -Wall
>
> # Append required CFLAGS
> override CFLAGS += $(CONFIG_FLAGS) $(INCLUDES) $(PLUGIN_DIR_SQ)
> +override CFLAGS += $(udis86-flags)
>
> ifeq ($(VERBOSE),1)
> Q =
> @@ -228,7 +237,7 @@ do_compile_plugin_obj = \
>
> do_plugin_build = \
> ($(print_plugin_build) \
> - $(CC) -shared -nostartfiles -o $@ $<)
> + $(CC) $(CFLAGS) -shared -nostartfiles -o $@ $<)
>
> do_build_static_lib = \
> ($(print_static_lib_build) \
> diff --git a/plugin_kvm.c b/plugin_kvm.c
> index 7217e85..00cac5a 100644
> --- a/plugin_kvm.c
> +++ b/plugin_kvm.c
> @@ -21,9 +21,68 @@
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> +#include <stdint.h>
>
> #include "parse-events.h"
>
> +#ifdef HAVE_UDIS86
> +
> +#include <udis86.h>
> +
> +static ud_t ud;
> +
> +static void init_disassembler(void)
> +{
> + ud_init(&ud);
> + ud_set_syntax(&ud, UD_SYN_ATT);
> +}
> +
> +static const char *disassemble(unsigned char *insn, int len, uint64_t rip,
> + int cr0_pe, int eflags_vm,
> + int cs_d, int cs_l)
> +{
> + int mode;
> +
> + if (!cr0_pe)
> + mode = 16;
> + else if (eflags_vm)
> + mode = 16;
> + else if (cs_l)
> + mode = 64;
> + else if (cs_d)
> + mode = 32;
> + else
> + mode = 16;
> +
> + ud_set_pc(&ud, rip);
> + ud_set_mode(&ud, mode);
> + ud_set_input_buffer(&ud, insn, len);
> + ud_disassemble(&ud);
> + return ud_insn_asm(&ud);
> +}
> +
> +#else
> +
> +static void init_disassembler(void)
> +{
> +}
> +
> +static const char *disassemble(unsigned char *insn, int len, uint64_t rip,
> + int cr0_pe, int eflags_vm,
> + int cs_d, int cs_l)
> +{
> + static char out[15*3+1];
> + int i;
> +
> + for (i = 0; i < len; ++i)
> + sprintf(out + i * 3, "%02x ", insn[i]);
> + out[len*3-1] = '\0';
> + return out;
> +}
> +
> +#endif
> +
> +
> #define VMX_EXIT_REASONS \
> _ER(EXCEPTION_NMI, 0) \
> _ER(EXTERNAL_INTERRUPT, 1) \
> @@ -99,6 +158,53 @@ static int kvm_exit_handler(struct trace_seq *s, struct record *record,
> return 0;
> }
>
> +#define KVM_EMUL_INSN_F_CR0_PE (1 << 0)
> +#define KVM_EMUL_INSN_F_EFL_VM (1 << 1)
> +#define KVM_EMUL_INSN_F_CS_D (1 << 2)
> +#define KVM_EMUL_INSN_F_CS_L (1 << 3)
> +
> +static int kvm_emulate_insn_handler(struct trace_seq *s, struct record *record,
> + struct event_format *event, void *context)
> +{
> + unsigned long long rip, csbase, len, flags, failed;
> + int llen;
> + uint8_t *insn;
> + const char *disasm;
> +
> + if (pevent_get_field_val(s, event, "rip", record, &rip, 1) < 0)
> + return -1;
> +
> + if (pevent_get_field_val(s, event, "csbase", record, &csbase, 1) < 0)
> + return -1;
> +
> + if (pevent_get_field_val(s, event, "len", record, &len, 1) < 0)
> + return -1;
> +
> + if (pevent_get_field_val(s, event, "flags", record, &flags, 1) < 0)
> + return -1;
> +
> + if (pevent_get_field_val(s, event, "failed", record, &failed, 1) < 0)
> + return -1;
> +
> + insn = pevent_get_field_raw(s, event, "insn", record, &llen, 1);
> + if (!insn)
> + return -1;
> +
> + disasm = disassemble(insn, len, rip,
> + flags & KVM_EMUL_INSN_F_CR0_PE,
> + flags & KVM_EMUL_INSN_F_EFL_VM,
> + flags & KVM_EMUL_INSN_F_CS_D,
> + flags & KVM_EMUL_INSN_F_CS_L);
> +
> + trace_seq_printf(s, "%llx:%llx: %s%s", csbase, rip, disasm,
> + failed ? " FAIL" : "");
> +
> + pevent_print_num_field(s, " rip %0xlx", event, "guest_rip", record, 1);
> +
> + return 0;
> +}
> +
> +
> static int kvm_nested_vmexit_inject_handler(struct trace_seq *s, struct record *record,
> struct event_format *event, void *context)
> {
> @@ -199,9 +305,14 @@ static int kvm_mmu_get_page_handler(struct trace_seq *s, struct record *record,
>
> int PEVENT_PLUGIN_LOADER(struct pevent *pevent)
> {
> + init_disassembler();
> +
> pevent_register_event_handler(pevent, -1, "kvm", "kvm_exit",
> kvm_exit_handler, NULL);
>
> + pevent_register_event_handler(pevent, -1, "kvm", "kvm_emulate_insn",
> + kvm_emulate_insn_handler, NULL);
> +
> pevent_register_event_handler(pevent, -1, "kvm", "kvm_nested_vmexit",
> kvm_nested_vmexit_handler, NULL);
>
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