From 772f1b3721ac138b69c525cb2186b6d72ed200e1 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Wed, 23 Jan 2019 12:00:15 +0000 Subject: [PATCH] trace: forbid use of %m in trace event format strings MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The '%m' format instructs glibc's printf()/syslog() implementation to insert the contents of strerror(errno). Since this is a glibc extension it should generally be avoided in QEMU due to need for portability to a variety of platforms. Even though vfio is Linux-only code that could otherwise use "%m", it must still be avoided in trace-events files because several of the backends do not use the format string and so this error information is invisible to them. The errno string value should be given as an explicit trace argument instead, making it accessible to all backends. This also allows it to work correctly with future patches that use the format string with systemtap's simple printf code. Reviewed-by: Eric Blake Signed-off-by: Daniel P. Berrangé Message-id: 20190123120016.4538-4-berrange@redhat.com Signed-off-by: Stefan Hajnoczi --- hw/vfio/pci.c | 2 +- hw/vfio/trace-events | 2 +- scripts/tracetool/__init__.py | 4 ++++ 3 files changed, 6 insertions(+), 2 deletions(-) diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c index c0cb1ec289..dd12f36391 100644 --- a/hw/vfio/pci.c +++ b/hw/vfio/pci.c @@ -2581,7 +2581,7 @@ static void vfio_populate_device(VFIOPCIDevice *vdev, Error **errp) ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_IRQ_INFO, &irq_info); if (ret) { /* This can fail for an old kernel or legacy PCI dev */ - trace_vfio_populate_device_get_irq_info_failure(); + trace_vfio_populate_device_get_irq_info_failure(strerror(errno)); } else if (irq_info.count == 1) { vdev->pci_aer = true; } else { diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events index a85e8662ea..f41ca96160 100644 --- a/hw/vfio/trace-events +++ b/hw/vfio/trace-events @@ -37,7 +37,7 @@ vfio_pci_hot_reset_has_dep_devices(const char *name) "%s: hot reset dependent de vfio_pci_hot_reset_dep_devices(int domain, int bus, int slot, int function, int group_id) "\t%04x:%02x:%02x.%x group %d" vfio_pci_hot_reset_result(const char *name, const char *result) "%s hot reset: %s" vfio_populate_device_config(const char *name, unsigned long size, unsigned long offset, unsigned long flags) "Device %s config:\n size: 0x%lx, offset: 0x%lx, flags: 0x%lx" -vfio_populate_device_get_irq_info_failure(void) "VFIO_DEVICE_GET_IRQ_INFO failure: %m" +vfio_populate_device_get_irq_info_failure(const char *errstr) "VFIO_DEVICE_GET_IRQ_INFO failure: %s" vfio_realize(const char *name, int group_id) " (%s) group %d" vfio_mdev(const char *name, bool is_mdev) " (%s) is_mdev %d" vfio_add_ext_cap_dropped(const char *name, uint16_t cap, uint16_t offset) "%s 0x%x@0x%x" diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py index 3478ac93ab..6fca674936 100644 --- a/scripts/tracetool/__init__.py +++ b/scripts/tracetool/__init__.py @@ -274,6 +274,10 @@ class Event(object): props = groups["props"].split() fmt = groups["fmt"] fmt_trans = groups["fmt_trans"] + if fmt.find("%m") != -1 or fmt_trans.find("%m") != -1: + raise ValueError("Event format '%m' is forbidden, pass the error " + "as an explicit trace argument") + if len(fmt_trans) > 0: fmt = [fmt_trans, fmt] args = Arguments.build(groups["args"]) -- 2.11.4.GIT