[Qemu-devel] [PATCH v2 2/4] pc-bios/s390-ccw/net: Add support for pxelinux-style config files

[Thomas Huth <thuth@redhat.com>]

Since it is quite cumbersome to manually create a combined kernel with
initrd image for network booting, we now support loading via pxelinux
configuration files, too. In these files, the kernel, initrd and command
line parameters can be specified seperately, and the firmware then takes
care of glueing everything together in memory after the files have been
downloaded.

The user can either specify a config file directly as bootfile via DHCP
(but in this case, the file has to start either with "default" or a "#"
comment so we can distinguish it from binary kernels), or a folder (i.e.
the bootfile name must end with "/") where the firmware should look for
the typical pxelinux.cfg file names based on MAC or IP address. If no
direct file or folder has been specified, we still look for certain
files in the default "pxelinux.cfg/" folder, but omit some of the file
names to avoid to download x86 config files here by mistake.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 pc-bios/s390-ccw/netboot.mak |   5 +-
 pc-bios/s390-ccw/netmain.c   | 225 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 222 insertions(+), 8 deletions(-)

diff --git a/pc-bios/s390-ccw/netboot.mak b/pc-bios/s390-ccw/netboot.mak
index a25d238..8db9573 100644
--- a/pc-bios/s390-ccw/netboot.mak
+++ b/pc-bios/s390-ccw/netboot.mak
@@ -24,8 +24,9 @@ CTYPE_OBJS = isdigit.o isxdigit.o toupper.o
 %.o : $(SLOF_DIR)/lib/libc/ctype/%.c
 	$(call quiet-command,$(CC) $(LIBC_CFLAGS) -c -o $@ $<,"CC","$(TARGET_DIR)$@")
 
-STRING_OBJS = strcat.o strchr.o strcmp.o strcpy.o strlen.o strncmp.o strncpy.o \
-	      strstr.o memset.o memcpy.o memmove.o memcmp.o
+STRING_OBJS = strcasecmp.o strcat.o strchr.o strcmp.o strcpy.o strlen.o \
+	      strncasecmp.o strncmp.o strncpy.o strstr.o \
+	      memset.o memcpy.o memmove.o memcmp.o
 %.o : $(SLOF_DIR)/lib/libc/string/%.c
 	$(call quiet-command,$(CC) $(LIBC_CFLAGS) -c -o $@ $<,"CC","$(TARGET_DIR)$@")
 
diff --git a/pc-bios/s390-ccw/netmain.c b/pc-bios/s390-ccw/netmain.c
index 8fa9e6c..129f009 100644
--- a/pc-bios/s390-ccw/netmain.c
+++ b/pc-bios/s390-ccw/netmain.c
@@ -39,11 +39,17 @@
 
 extern char _start[];
 
+#define KERNEL_ADDR             ((void *)0L)
+#define KERNEL_MAX_SIZE         ((long)_start)
+#define ARCH_COMMAND_LINE_SIZE  896              /* Taken from Linux kernel */
+
 char stack[PAGE_SIZE * 8] __attribute__((aligned(PAGE_SIZE)));
 IplParameterBlock iplb __attribute__((aligned(PAGE_SIZE)));
+static char cfgbuf[2048];
 
 static SubChannelId net_schid = { .one = 1 };
 static int ip_version = 4;
+static uint8_t mac[6];
 static uint64_t dest_timer;
 
 static uint64_t get_timer_ms(void)
@@ -136,9 +142,15 @@ static int tftp_load(filename_ip_t *fnip, void *buffer, int len)
     rc = tftp(fnip, buffer, len, DEFAULT_TFTP_RETRIES, &tftp_err, 1, 1428,
               ip_version);
 
-    if (rc > 0) {
-        printf("  TFTP: Received %s (%d KBytes)\n", fnip->filename,
-               rc / 1024);
+    if (rc < 0) {
+        /* Make sure that error messages are put into a new line */
+        printf("\n  ");
+    }
+
+    if (rc > 1024) {
+        printf("  TFTP: Received %s (%d KBytes)\n", fnip->filename, rc / 1024);
+    } else if (rc > 0) {
+        printf("  TFTP: Received %s (%d Bytes)\n", fnip->filename, rc);
     } else if (rc == -1) {
         puts("unknown TFTP error");
     } else if (rc == -2) {
@@ -201,7 +213,6 @@ static int tftp_load(filename_ip_t *fnip, void *buffer, int len)
 
 static int net_init(filename_ip_t *fn_ip)
 {
-    uint8_t mac[6];
     int rc;
 
     memset(fn_ip, 0, sizeof(filename_ip_t));
@@ -275,6 +286,202 @@ static void net_release(filename_ip_t *fn_ip)
     }
 }
 
+/* This structure holds the data from one pxelinux.cfg file entry */
+struct lkia {
+    const char *label;
+    const char *kernel;
+    const char *initrd;
+    const char *append;
+};
+
+static int load_kernel_with_initrd(filename_ip_t *fn_ip, struct lkia *kia)
+{
+    int rc;
+
+    printf("Loading pxelinux.cfg entry '%s'\n", kia->label);
+
+    if (!kia->kernel) {
+        printf("Kernel entry is missing!\n");
+        return -1;
+    }
+
+    strncpy((char *)&fn_ip->filename, kia->kernel, sizeof(fn_ip->filename));
+    rc = tftp_load(fn_ip, KERNEL_ADDR, KERNEL_MAX_SIZE);
+    if (rc < 0) {
+        return rc;
+    }
+
+    if (kia->initrd) {
+        uint64_t iaddr = (rc + 0xfff) & ~0xfffUL;
+
+        strncpy((char *)&fn_ip->filename, kia->initrd, sizeof(fn_ip->filename));
+        rc = tftp_load(fn_ip, (void *)iaddr, KERNEL_MAX_SIZE - iaddr);
+        if (rc < 0) {
+            return rc;
+        }
+        /* Patch location and size: */
+        *(uint64_t *)0x10408 = iaddr;
+        *(uint64_t *)0x10410 = rc;
+        rc += iaddr;
+    }
+
+    if (kia->append) {
+        strncpy((char *)0x10480, kia->append, ARCH_COMMAND_LINE_SIZE);
+    }
+
+    return rc;
+}
+
+#define MAX_PXELINUX_ENTRIES 16
+
+/**
+ * Parse a pxelinux-style configuration file.
+ * See the following URL for more inforation about the config file syntax:
+ * https://www.syslinux.org/wiki/index.php?title=PXELINUX
+ */
+static int handle_pxelinux_cfg(filename_ip_t *fn_ip, char *cfg, int cfgsize)
+{
+    struct lkia entries[MAX_PXELINUX_ENTRIES];
+    int num_entries = 0;
+    char *ptr = cfg, *eol, *arg;
+    char *defaultlabel = NULL;
+    int def_ent = 0;
+
+    while (ptr < cfg + cfgsize && num_entries < MAX_PXELINUX_ENTRIES) {
+        eol = strchr(ptr, '\n');
+        if (!eol) {
+            eol = cfg + cfgsize;
+        }
+        if (eol > ptr && *(eol - 1) == '\r') {
+            *(eol - 1) = 0;
+        }
+        *eol = '\0';
+        while (*ptr == ' ' || *ptr == '\t') {
+            ptr++;
+        }
+        if (*ptr == 0 || *ptr == '#') {   /* Ignore comments and empty lines */
+            goto nextline;
+        }
+        arg = strchr(ptr, ' ');    /* Look for space between command and arg */
+        if (!arg) {
+            arg = strchr(ptr, '\t');
+        }
+        if (!arg) {
+            printf("Failed to parse the following line:\n %s\n", ptr);
+            goto nextline;
+        }
+        *arg++ = 0;
+        while (*arg == ' ' || *arg == '\t') {
+            arg++;
+        }
+        if (!strcasecmp("default", ptr)) {
+            defaultlabel = arg;
+        } else if (!strcasecmp("label", ptr)) {
+            entries[num_entries].label = arg;
+            if (defaultlabel && !strcmp(arg, defaultlabel)) {
+                def_ent = num_entries;
+            }
+            num_entries++;
+        } else if (!strcasecmp("kernel", ptr) && num_entries > 0) {
+            entries[num_entries - 1].kernel = arg;
+        } else if (!strcasecmp("initrd", ptr) && num_entries > 0) {
+            entries[num_entries - 1].initrd = arg;
+        } else if (!strcasecmp("append", ptr) && num_entries > 0) {
+            entries[num_entries - 1].append = arg;
+        } else {
+            printf("Command '%s' is not supported.\n", ptr);
+        }
+nextline:
+        ptr = eol + 1;
+    }
+
+    return load_kernel_with_initrd(fn_ip, &entries[def_ent]);
+}
+
+static int net_try_pxelinux_cfgs(filename_ip_t *fn_ip)
+{
+    int rc, idx;
+    char basedir[256];
+    int has_basedir;
+
+    cfgbuf[sizeof(cfgbuf) - 1] = 0;   /* Make sure that it is NUL-terminated */
+
+    /* Did we get a usable base directory via DHCP? */
+    idx = strlen((char *)fn_ip->filename);
+    if (idx > 0 && idx < sizeof(basedir) - 40 &&
+        fn_ip->filename[idx - 1] == '/') {
+        has_basedir = true;
+        strcpy(basedir, (char *)fn_ip->filename);
+    } else {
+        has_basedir = false;
+        strcpy(basedir, "pxelinux.cfg/");
+    }
+
+    printf("Trying pxelinux.cfg files...\n");
+
+    /* Look for config file with MAC address in its name */
+    sprintf((char *)fn_ip->filename, "%s%02x-%02x-%02x-%02x-%02x-%02x",
+            basedir, mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
+    rc = tftp_load(fn_ip, cfgbuf, sizeof(cfgbuf) - 1);
+    if (rc > 0) {
+        return handle_pxelinux_cfg(fn_ip, cfgbuf, sizeof(cfgbuf));
+    }
+
+    /* Look for config file with IP address in its name */
+    if (ip_version == 4) {
+        for (idx = 0; (has_basedir && idx <= 7) || idx < 1; idx++) {
+            sprintf((char *)fn_ip->filename, "%s%02X%02X%02X%02X", basedir,
+                    (fn_ip->own_ip >> 24) & 0xff, (fn_ip->own_ip >> 16) & 0xff,
+                    (fn_ip->own_ip >> 8) & 0xff, fn_ip->own_ip & 0xff);
+            fn_ip->filename[strlen((char *)fn_ip->filename) - idx] = 0;
+            rc = tftp_load(fn_ip, cfgbuf, sizeof(cfgbuf) - 1);
+            if (rc > 0) {
+                return handle_pxelinux_cfg(fn_ip, cfgbuf, sizeof(cfgbuf));
+            }
+        }
+    }
+
+    /* Try "default" config file */
+    if (has_basedir) {
+        sprintf((char *)fn_ip->filename, "%sdefault", basedir);
+        rc = tftp_load(fn_ip, cfgbuf, sizeof(cfgbuf) - 1);
+        if (rc > 0) {
+            return handle_pxelinux_cfg(fn_ip, cfgbuf, sizeof(cfgbuf));
+        }
+    }
+
+    return -1;
+}
+
+static int net_try_direct_tftp_load(filename_ip_t *fn_ip)
+{
+    int rc;
+    void *baseaddr = (void *)0x2000;  /* Load right after the low-core */
+
+    rc = tftp_load(fn_ip, baseaddr, KERNEL_MAX_SIZE - (long)baseaddr);
+    if (rc < 0) {
+        return rc;
+    } else if (rc < 8) {
+        printf("'%s' is too small (%i bytes only).\n", fn_ip->filename, rc);
+        return -1;
+    }
+
+    /* Check whether it is a configuration file instead of a kernel */
+    if (rc < sizeof(cfgbuf) - 1) {
+        memcpy(cfgbuf, baseaddr, rc);
+        cfgbuf[rc] = 0;    /* Make sure that it is NUL-terminated */
+        if (!strncasecmp("default", cfgbuf, 7) || !strncmp("# ", cfgbuf, 2)) {
+            /* Looks like it is a pxelinux.cfg */
+            return handle_pxelinux_cfg(fn_ip, cfgbuf, rc);
+        }
+    }
+
+    /* Move kernel to right location */
+    memmove(KERNEL_ADDR, baseaddr, rc);
+
+    return rc;
+}
+
 void panic(const char *string)
 {
     sclp_print(string);
@@ -347,7 +554,7 @@ static void virtio_setup(void)
 void main(void)
 {
     filename_ip_t fn_ip;
-    int rc;
+    int rc, fnlen;
 
     sclp_setup();
     sclp_print("Network boot starting...\n");
@@ -359,7 +566,13 @@ void main(void)
         panic("Network initialization failed. Halting.\n");
     }
 
-    rc = tftp_load(&fn_ip, NULL, (long)_start);
+    fnlen = strlen((char *)fn_ip.filename);
+    if (fnlen > 0 && fn_ip.filename[fnlen - 1] != '/') {
+        rc = net_try_direct_tftp_load(&fn_ip);
+    }
+    if (rc <= 0) {
+        rc = net_try_pxelinux_cfgs(&fn_ip);
+    }
 
     net_release(&fn_ip);
 
-- 
1.8.3.1