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SubjectRE: [PATCH v3 3/3] tools: hv: Add new fcopy application based on uio driver
Date


> -----Original Message-----
> From: Michael Kelley (LINUX) <mikelley@microsoft.com>
> Sent: Thursday, August 3, 2023 3:15 AM
> To: Saurabh Sengar <ssengar@linux.microsoft.com>; KY Srinivasan
> <kys@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>;
> wei.liu@kernel.org; Dexuan Cui <decui@microsoft.com>;
> gregkh@linuxfoundation.org; corbet@lwn.net; linux-kernel@vger.kernel.org;
> linux-hyperv@vger.kernel.org; linux-doc@vger.kernel.org
> Subject: [EXTERNAL] RE: [PATCH v3 3/3] tools: hv: Add new fcopy application
> based on uio driver
>
> From: Saurabh Sengar <ssengar@linux.microsoft.com> Sent: Friday, July 14,
> 2023 3:26 AM
> >
> > Implement the file copy service for Linux guests on Hyper-V. This
> > permits the host to copy a file (over VMBus) into the guest. This
> > facility is part of "guest integration services" supported on the
> > Hyper-V platform.
> >
> > Here is a link that provides additional details on this functionality:
> >
> > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Flear
> > n.microsoft.com%2Fen-us%2Fpowershell%2Fmodule%2Fhyper-v%2Fcopy-
> vmfile%
> > 3Fview%3Dwindowsserver2022-
> ps&data=05%7C01%7Cssengar%40microsoft.com%7
> >
> Ca5edc1b9d6574e2e6e3108db93a1c558%7C72f988bf86f141af91ab2d7cd011
> db47%7
> >
> C1%7C0%7C638266095311741847%7CUnknown%7CTWFpbGZsb3d8eyJWIjoi
> MC4wLjAwMD
> >
> AiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C
> &sdata
> > =VudSwIKYJJJgPKxNbbfCnOjia1lfKCdijnSn94OWm8Q%3D&reserved=0
> >
> > This new fcopy application uses uio_hv_vmbus_client driver which makes
> > the earlier hv_util based driver and application obsolete.
> >
> > Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> > ---
> > [V3]
> > - Improve cover letter and commit messages
> > - Improve debug prints
> > - Instead of hardcoded instance id, query from class id sysfs
> > - Set the ring_size value from application
> > - Update the application to mmap /dev/uio instead of sysfs
> > - new application compilation dependent on x86
> >
> > [V2]
> > - simpler sysfs path
> >
> > tools/hv/Build | 1 +
> > tools/hv/Makefile | 10 +-
> > tools/hv/hv_fcopy_uio_daemon.c | 578
> > +++++++++++++++++++++++++++++++++
> > 3 files changed, 588 insertions(+), 1 deletion(-) create mode 100644
> > tools/hv/hv_fcopy_uio_daemon.c
> >
> > diff --git a/tools/hv/Build b/tools/hv/Build index
> > 2a667d3d94cb..efcbb74a0d23 100644
> > --- a/tools/hv/Build
> > +++ b/tools/hv/Build
> > @@ -2,3 +2,4 @@ hv_kvp_daemon-y += hv_kvp_daemon.o
> hv_vss_daemon-y +=
> > hv_vss_daemon.o hv_fcopy_daemon-y += hv_fcopy_daemon.o
> > vmbus_bufring-y += vmbus_bufring.o
> > +hv_fcopy_uio_daemon-y += hv_fcopy_uio_daemon.o
> > diff --git a/tools/hv/Makefile b/tools/hv/Makefile index
> > 33cf488fd20f..678c6c450a53 100644
> > --- a/tools/hv/Makefile
> > +++ b/tools/hv/Makefile
> > @@ -21,8 +21,10 @@ override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -
> > I$(OUTPUT)include
> >
> > ifeq ($(SRCARCH),x86)
> > ALL_LIBS := libvmbus_bufring.a
> > -endif
> > +ALL_TARGETS := hv_kvp_daemon hv_vss_daemon hv_fcopy_daemon
> > hv_fcopy_uio_daemon
> > +else
> > ALL_TARGETS := hv_kvp_daemon hv_vss_daemon hv_fcopy_daemon
> > +endif
> > ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS)) $(patsubst
> > %,$(OUTPUT)%,$(ALL_LIBS))
> >
> > ALL_SCRIPTS := hv_get_dhcp_info.sh hv_get_dns_info.sh
> > hv_set_ifconfig.sh @@ -56,6 +58,12 @@ $(HV_FCOPY_DAEMON_IN):
> FORCE
> > $(OUTPUT)hv_fcopy_daemon: $(HV_FCOPY_DAEMON_IN)
> > $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@
> >
> > +HV_FCOPY_UIO_DAEMON_IN := $(OUTPUT)hv_fcopy_uio_daemon-in.o
> > +$(HV_FCOPY_UIO_DAEMON_IN): FORCE
> > + $(Q)$(MAKE) $(build)=hv_fcopy_uio_daemon
> > +$(OUTPUT)hv_fcopy_uio_daemon: $(HV_FCOPY_UIO_DAEMON_IN)
> > libvmbus_bufring.a
> > + $(QUIET_LINK)$(CC) -lm $< -L. -lvmbus_bufring -o $@
> > +
> > clean:
> > rm -f $(ALL_PROGRAMS)
> > find $(or $(OUTPUT),.) -name '*.o' -delete -o -name '\.*.d' -delete
> > diff --git a/tools/hv/hv_fcopy_uio_daemon.c
> > b/tools/hv/hv_fcopy_uio_daemon.c new file mode 100644 index
> > 000000000000..e8618a30dc7e
> > --- /dev/null
> > +++ b/tools/hv/hv_fcopy_uio_daemon.c
> > @@ -0,0 +1,578 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * An implementation of host to guest copy functionality for Linux.
> > + *
> > + * Copyright (C) 2023, Microsoft, Inc.
> > + *
> > + * Author : K. Y. Srinivasan <kys@microsoft.com>
> > + * Author : Saurabh Sengar <ssengar@microsoft.com>
> > + *
> > + */
> > +
> > +#include <dirent.h>
> > +#include <errno.h>
> > +#include <fcntl.h>
> > +#include <getopt.h>
> > +#include <locale.h>
> > +#include <stdbool.h>
> > +#include <stddef.h>
> > +#include <stdint.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <syslog.h>
> > +#include <unistd.h>
> > +#include <sys/mman.h>
> > +#include <sys/stat.h>
> > +#include <linux/hyperv.h>
> > +#include "vmbus_bufring.h"
> > +
> > +#define ICMSGTYPE_NEGOTIATE 0
> > +#define ICMSGTYPE_FCOPY 7
> > +
> > +#define WIN8_SRV_MAJOR 1
> > +#define WIN8_SRV_MINOR 1
> > +#define WIN8_SRV_VERSION (WIN8_SRV_MAJOR << 16 |
> WIN8_SRV_MINOR)
> > +
> > +#define MAX_PATH_LEN 300
> > +#define MAX_LINE_LEN 40
> > +#define DEVICES_SYSFS "/sys/bus/vmbus/devices"
> > +#define FCOPY_CLASS_ID "34d14be3-dee4-41c8-9ae7-
> 6b174977c192"
> > +
> > +#define FCOPY_VER_COUNT 1
> > +static const int fcopy_versions[] = {
> > + WIN8_SRV_VERSION
> > +};
> > +
> > +#define FW_VER_COUNT 1
> > +static const int fw_versions[] = {
> > + UTIL_FW_VERSION
> > +};
> > +
> > +#define HV_RING_SIZE (4 * 4096)
> > +
> > +unsigned char desc[HV_RING_SIZE];
> > +
> > +static int target_fd;
> > +static char target_fname[PATH_MAX];
> > +static unsigned long long filesize;
> > +
> > +static int hv_fcopy_create_file(char *file_name, char *path_name,
> > +__u32 flags) {
> > + int error = HV_E_FAIL;
> > + char *q, *p;
> > +
> > + filesize = 0;
> > + p = (char *)path_name;
> > + snprintf(target_fname, sizeof(target_fname), "%s/%s",
> > + (char *)path_name, (char *)file_name);
> > +
> > + /*
> > + * Check to see if the path is already in place; if not,
> > + * create if required.
> > + */
> > + while ((q = strchr(p, '/')) != NULL) {
> > + if (q == p) {
> > + p++;
> > + continue;
> > + }
> > + *q = '\0';
> > + if (access(path_name, F_OK)) {
> > + if (flags & CREATE_PATH) {
> > + if (mkdir(path_name, 0755)) {
> > + syslog(LOG_ERR, "Failed to create
> %s",
> > + path_name);
> > + goto done;
> > + }
> > + } else {
> > + syslog(LOG_ERR, "Invalid path: %s",
> path_name);
> > + goto done;
> > + }
> > + }
> > + p = q + 1;
> > + *q = '/';
> > + }
> > +
> > + if (!access(target_fname, F_OK)) {
> > + syslog(LOG_INFO, "File: %s exists", target_fname);
> > + if (!(flags & OVER_WRITE)) {
> > + error = HV_ERROR_ALREADY_EXISTS;
> > + goto done;
> > + }
> > + }
> > +
> > + target_fd = open(target_fname,
> > + O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC,
> 0744);
> > + if (target_fd == -1) {
> > + syslog(LOG_INFO, "Open Failed: %s", strerror(errno));
> > + goto done;
> > + }
> > +
> > + error = 0;
> > +done:
> > + if (error)
> > + target_fname[0] = '\0';
> > + return error;
> > +}
> > +
> > +static int hv_copy_data(struct hv_do_fcopy *cpmsg) {
> > + ssize_t bytes_written;
> > + int ret = 0;
> > +
> > + bytes_written = pwrite(target_fd, cpmsg->data, cpmsg->size,
> > + cpmsg->offset);
> > +
> > + filesize += cpmsg->size;
> > + if (bytes_written != cpmsg->size) {
> > + switch (errno) {
> > + case ENOSPC:
> > + ret = HV_ERROR_DISK_FULL;
> > + break;
> > + default:
> > + ret = HV_E_FAIL;
> > + break;
> > + }
> > + syslog(LOG_ERR, "pwrite failed to write %llu bytes: %ld (%s)",
> > + filesize, (long)bytes_written, strerror(errno));
> > + }
> > +
> > + return ret;
> > +}
> > +
> > +/*
> > + * Reset target_fname to "" in the two below functions for
> > +hibernation: if
> > + * the fcopy operation is aborted by hibernation, the daemon should
> > +remove the
> > + * partially-copied file; to achieve this, the hv_utils driver always
> > +fakes a
> > + * CANCEL_FCOPY message upon suspend, and later when the VM
> resumes
> > +back,
> > + * the daemon calls hv_copy_cancel() to remove the file; if a file is
> > +copied
> > + * successfully before suspend, hv_copy_finished() must reset
> > +target_fname to
> > + * avoid that the file can be incorrectly removed upon resume, since
> > +the faked
> > + * CANCEL_FCOPY message is spurious in this case.
> > + */
> > +static int hv_copy_finished(void)
> > +{
> > + close(target_fd);
> > + target_fname[0] = '\0';
> > + return 0;
> > +}
> > +
> > +static void print_usage(char *argv[]) {
> > + fprintf(stderr, "Usage: %s [options]\n"
> > + "Options are:\n"
> > + " -n, --no-daemon stay in foreground, don't
> daemonize\n"
> > + " -h, --help print this help\n", argv[0]);
> > +}
> > +
> > +static bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
> unsigned char *buf,
> > + unsigned int buflen, const int *fw_version,
> int fw_vercnt,
> > + const int *srv_version, int srv_vercnt,
> > + int *nego_fw_version, int *nego_srv_version)
> {
> > + int icframe_major, icframe_minor;
> > + int icmsg_major, icmsg_minor;
> > + int fw_major, fw_minor;
> > + int srv_major, srv_minor;
> > + int i, j;
> > + bool found_match = false;
> > + struct icmsg_negotiate *negop;
> > +
> > + /* Check that there's enough space for icframe_vercnt, icmsg_vercnt
> */
> > + if (buflen < ICMSG_HDR + offsetof(struct icmsg_negotiate, reserved)) {
> > + syslog(LOG_ERR, "Invalid icmsg negotiate");
> > + return false;
> > + }
> > +
> > + icmsghdrp->icmsgsize = 0x10;
> > + negop = (struct icmsg_negotiate *)&buf[ICMSG_HDR];
> > +
> > + icframe_major = negop->icframe_vercnt;
> > + icframe_minor = 0;
> > +
> > + icmsg_major = negop->icmsg_vercnt;
> > + icmsg_minor = 0;
> > +
> > + /* Validate negop packet */
> > + if (icframe_major > IC_VERSION_NEGOTIATION_MAX_VER_COUNT ||
> > + icmsg_major > IC_VERSION_NEGOTIATION_MAX_VER_COUNT ||
> > + ICMSG_NEGOTIATE_PKT_SIZE(icframe_major, icmsg_major) >
> buflen) {
> > + syslog(LOG_ERR, "Invalid icmsg negotiate - icframe_major:
> %u, icmsg_major: %u\n",
> > + icframe_major, icmsg_major);
> > + goto fw_error;
> > + }
> > +
> > + /*
> > + * Select the framework version number we will
> > + * support.
> > + */
> > +
> > + for (i = 0; i < fw_vercnt; i++) {
> > + fw_major = (fw_version[i] >> 16);
> > + fw_minor = (fw_version[i] & 0xFFFF);
> > +
> > + for (j = 0; j < negop->icframe_vercnt; j++) {
> > + if (negop->icversion_data[j].major == fw_major &&
> > + negop->icversion_data[j].minor == fw_minor) {
> > + icframe_major = negop-
> >icversion_data[j].major;
> > + icframe_minor = negop-
> >icversion_data[j].minor;
> > + found_match = true;
> > + break;
> > + }
> > + }
> > +
> > + if (found_match)
> > + break;
> > + }
> > +
> > + if (!found_match)
> > + goto fw_error;
> > +
> > + found_match = false;
> > +
> > + for (i = 0; i < srv_vercnt; i++) {
> > + srv_major = (srv_version[i] >> 16);
> > + srv_minor = (srv_version[i] & 0xFFFF);
> > +
> > + for (j = negop->icframe_vercnt;
> > + (j < negop->icframe_vercnt + negop->icmsg_vercnt);
> > + j++) {
> > + if (negop->icversion_data[j].major == srv_major &&
> > + negop->icversion_data[j].minor == srv_minor) {
> > + icmsg_major = negop-
> >icversion_data[j].major;
> > + icmsg_minor = negop-
> >icversion_data[j].minor;
> > + found_match = true;
> > + break;
> > + }
> > + }
> > +
> > + if (found_match)
> > + break;
> > + }
> > +
> > + /*
> > + * Respond with the framework and service
> > + * version numbers we can support.
> > + */
> > +fw_error:
> > + if (!found_match) {
> > + negop->icframe_vercnt = 0;
> > + negop->icmsg_vercnt = 0;
> > + } else {
> > + negop->icframe_vercnt = 1;
> > + negop->icmsg_vercnt = 1;
> > + }
> > +
> > + if (nego_fw_version)
> > + *nego_fw_version = (icframe_major << 16) | icframe_minor;
> > +
> > + if (nego_srv_version)
> > + *nego_srv_version = (icmsg_major << 16) | icmsg_minor;
> > +
> > + negop->icversion_data[0].major = icframe_major;
> > + negop->icversion_data[0].minor = icframe_minor;
> > + negop->icversion_data[1].major = icmsg_major;
> > + negop->icversion_data[1].minor = icmsg_minor;
> > +
> > + return found_match;
> > +}
> > +
> > +static void wcstoutf8(char *dest, const __u16 *src, size_t dest_size)
> > +{
> > + size_t len = 0;
> > +
> > + while (len < dest_size) {
> > + if (src[len] < 0x80)
> > + dest[len++] = (char)(*src++);
> > + else
> > + dest[len++] = 'X';
> > + }
> > +
> > + dest[len] = '\0';
> > +}
> > +
> > +static int hv_fcopy_start(struct hv_start_fcopy *smsg_in) {
> > + setlocale(LC_ALL, "en_US.utf8");
> > + size_t file_size, path_size;
> > + char *file_name, *path_name;
> > + char *in_file_name = (char *)smsg_in->file_name;
> > + char *in_path_name = (char *)smsg_in->path_name;
> > +
> > + file_size = wcstombs(NULL, (const wchar_t *restrict)in_file_name, 0) +
> 1;
> > + path_size = wcstombs(NULL, (const wchar_t *restrict)in_path_name,
> 0)
> > ++ 1;
> > +
> > + file_name = (char *)malloc(file_size * sizeof(char));
> > + path_name = (char *)malloc(path_size * sizeof(char));
> > +
> > + wcstoutf8(file_name, (__u16 *)in_file_name, file_size);
> > + wcstoutf8(path_name, (__u16 *)in_path_name, path_size);
> > +
> > + return hv_fcopy_create_file(file_name, path_name,
> > +smsg_in->copy_flags); }
> > +
> > +static int hv_fcopy_send_data(struct hv_fcopy_hdr *fcopy_msg, int
> > +recvlen) {
> > + int operation = fcopy_msg->operation;
> > +
> > + /*
> > + * The strings sent from the host are encoded in
> > + * utf16; convert it to utf8 strings.
> > + * The host assures us that the utf16 strings will not exceed
> > + * the max lengths specified. We will however, reserve room
> > + * for the string terminating character - in the utf16s_utf8s()
> > + * function we limit the size of the buffer where the converted
> > + * string is placed to W_MAX_PATH -1 to guarantee
> > + * that the strings can be properly terminated!
> > + */
> > +
> > + switch (operation) {
> > + case START_FILE_COPY:
> > + return hv_fcopy_start((struct hv_start_fcopy *)fcopy_msg);
> > + case WRITE_TO_FILE:
> > + return hv_copy_data((struct hv_do_fcopy *)fcopy_msg);
> > + case COMPLETE_FCOPY:
> > + return hv_copy_finished();
> > + }
> > +
> > + return HV_E_FAIL;
> > +}
> > +
> > +/* process the packet recv from host */ static int
> > +fcopy_pkt_process(struct vmbus_br *txbr) {
> > + int ret, offset, pktlen;
> > + int fcopy_srv_version;
> > + const struct vmbus_chanpkt_hdr *pkt;
> > + struct hv_fcopy_hdr *fcopy_msg;
> > + struct icmsg_hdr *icmsghdr;
> > +
> > + pkt = (const struct vmbus_chanpkt_hdr *)desc;
> > + offset = pkt->hlen << 3;
> > + pktlen = (pkt->tlen << 3) - offset;
> > + icmsghdr = (struct icmsg_hdr *)&desc[offset + sizeof(struct
> vmbuspipe_hdr)];
> > + icmsghdr->status = HV_E_FAIL;
> > +
> > + if (icmsghdr->icmsgtype == ICMSGTYPE_NEGOTIATE) {
> > + if (vmbus_prep_negotiate_resp(icmsghdr, desc + offset,
> pktlen, fw_versions,
> > + FW_VER_COUNT, fcopy_versions,
> FCOPY_VER_COUNT,
> > + NULL, &fcopy_srv_version)) {
> > + syslog(LOG_INFO, "FCopy IC version %d.%d",
> > + fcopy_srv_version >> 16, fcopy_srv_version &
> 0xFFFF);
> > + icmsghdr->status = 0;
> > + }
> > + } else if (icmsghdr->icmsgtype == ICMSGTYPE_FCOPY) {
> > + /* Ensure recvlen is big enough to contain hv_fcopy_hdr */
> > + if (pktlen < ICMSG_HDR + sizeof(struct hv_fcopy_hdr)) {
> > + syslog(LOG_ERR, "Invalid Fcopy hdr. Packet length too
> small: %u",
> > + pktlen);
> > + return -ENOBUFS;
> > + }
> > +
> > + fcopy_msg = (struct hv_fcopy_hdr *)&desc[offset +
> ICMSG_HDR];
> > + icmsghdr->status = hv_fcopy_send_data(fcopy_msg, pktlen);
> > + }
> > +
> > + icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION |
> ICMSGHDRFLAG_RESPONSE;
> > + ret = rte_vmbus_chan_send(txbr, 0x6, desc + offset, pktlen, 0);
> > + if (ret) {
> > + syslog(LOG_ERR, "Write to ringbuffer failed err: %d", ret);
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static void fcopy_get_first_folder(char *path, char *chan_no) {
> > + DIR *dir = opendir(path);
> > + struct dirent *entry;
> > +
> > + if (!dir) {
> > + syslog(LOG_ERR, "Failed to open directory (errno=%s).\n",
> strerror(errno));
> > + return;
> > + }
> > +
> > + while ((entry = readdir(dir)) != NULL) {
> > + if (entry->d_type == DT_DIR && strcmp(entry->d_name, ".")
> != 0 &&
> > + strcmp(entry->d_name, "..") != 0) {
> > + strcpy(chan_no, entry->d_name);
> > + break;
> > + }
> > + }
> > +
> > + closedir(dir);
> > +}
> > +
> > +static void fcopy_set_ring_size(char *path, char *inst, int size) {
> > + char ring_size_path[MAX_PATH_LEN] = {0};
> > + FILE *fd;
> > +
> > + snprintf(ring_size_path, sizeof(ring_size_path), "%s/%s/%s", path, inst,
> "ring_size");
> > + fd = fopen(ring_size_path, "w");
> > + if (!fd) {
> > + syslog(LOG_WARNING, "Failed to open ring_size file
> (errno=%s).\n", strerror(errno));
> > + return;
> > + }
> > + fprintf(fd, "%d", size);
>
> Check for and log an error if the new value isn't accepted by the kernel
> driver?
> The code is using a ring size value that should be accepted by the kernel
> driver, but weird stuff happens and it's probably better to know about it.

Ok, will add error check.

>
> > + fclose(fd);
> > +}
> > +
> > +static char *fcopy_read_sysfs(char *path, char *buf, int len) {
> > + FILE *fd;
> > + char *ret;
> > +
> > + fd = fopen(path, "r");
> > + if (!fd)
> > + return NULL;
> > +
> > + ret = fgets(buf, len, fd);
> > + fclose(fd);
> > +
> > + return ret;
> > +}
> > +
> > +static int fcopy_get_instance_id(char *path, char *class_id, char
> > +*inst) {
> > + DIR *dir = opendir(path);
> > + struct dirent *entry;
> > + char tmp_path[MAX_PATH_LEN] = {0};
> > + char line[MAX_LINE_LEN];
> > +
> > + if (!dir) {
> > + syslog(LOG_ERR, "Failed to open directory (errno=%s).\n",
> strerror(errno));
> > + return -EINVAL;
> > + }
> > +
> > + while ((entry = readdir(dir)) != NULL) {
> > + if (entry->d_type == DT_LNK && strcmp(entry->d_name, ".")
> != 0 &&
> > + strcmp(entry->d_name, "..") != 0) {
> > + /* search for the sysfs path with matching class_id */
> > + snprintf(tmp_path, sizeof(tmp_path), "%s/%s/%s",
> > + path, entry->d_name, "class_id");
> > + if (!fcopy_read_sysfs(tmp_path, line, MAX_LINE_LEN))
> > + continue;
> > +
> > + /* class id matches, now fetch the instance id from
> device_id */
> > + if (strstr(line, class_id)) {
> > + snprintf(tmp_path, sizeof(tmp_path),
> "%s/%s/%s",
> > + path, entry->d_name, "device_id");
> > + if (!fcopy_read_sysfs(tmp_path, line,
> MAX_LINE_LEN))
> > + continue;
> > + /* remove braces */
> > + strncpy(inst, line + 1, strlen(line) - 3);
> > + break;
> > + }
> > + }
> > + }
> > +
> > + closedir(dir);
> > + return 0;
>
> If this function doesn't find a matching class_id, it appears that it returns 0,
> but with the "inst" parameter unset. The caller will then proceed as if "inst"
> was set when it is actually an uninitialized stack variable. Probably need
> some better error detection and handling.

Good point !
Let me fix it in next version.

>
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > + int fcopy_fd = -1, tmp = 1;
> > + int daemonize = 1, long_index = 0, opt, ret = -EINVAL;
> > + struct vmbus_br txbr, rxbr;
> > + void *ring;
> > + uint32_t len = HV_RING_SIZE;
> > + char uio_name[10] = {0};
> > + char uio_dev_path[15] = {0};
> > + char uio_path[MAX_PATH_LEN] = {0};
> > + char inst[MAX_LINE_LEN] = {0};
> > +
> > + static struct option long_options[] = {
> > + {"help", no_argument, 0, 'h' },
> > + {"no-daemon", no_argument, 0, 'n' },
> > + {0, 0, 0, 0 }
> > + };
> > +
> > + while ((opt = getopt_long(argc, argv, "hn", long_options,
> > + &long_index)) != -1) {
> > + switch (opt) {
> > + case 'n':
> > + daemonize = 0;
> > + break;
> > + case 'h':
> > + default:
> > + print_usage(argv);
> > + exit(EXIT_FAILURE);
> > + }
> > + }
> > +
> > + if (daemonize && daemon(1, 0)) {
> > + syslog(LOG_ERR, "daemon() failed; error: %s",
> strerror(errno));
> > + exit(EXIT_FAILURE);
> > + }
> > +
> > + openlog("HV_UIO_FCOPY", 0, LOG_USER);
> > + syslog(LOG_INFO, "starting; pid is:%d", getpid());
> > +
> > + /* get instance id */
> > + if (fcopy_get_instance_id(DEVICES_SYSFS, FCOPY_CLASS_ID, inst))
> > + exit(EXIT_FAILURE);
>
> Per above, need better error handling. And since the syslog is now open, any
> errors should be logged rather than having the process just mysteriously exit.

OK.

- Saurabh

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