Patchwork v4 revamp acpitable parsing and allow to specify complete (headerful) table

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Submitter Michael Tokarev
Date April 5, 2011, 6:53 p.m.
Message ID <1302029596-10006-1-git-send-email-mjt@msgid.tls.msk.ru>
Download mbox | patch
Permalink /patch/89921/
State New
Headers show

Comments

Michael Tokarev - April 5, 2011, 6:53 p.m.
This patch almost rewrites acpi_table_add() function
(but still leaves it using old get_param_value() interface).
The result is that it's now possible to specify whole table
(together with a header) in an external file, instead of just
data portion, with a new file= parameter, but at the same time
it's still possible to specify header fields as before.

Now with the checkpatch.pl formatting fixes, thanks to
Stefan Hajnoczi for suggestions, with changes from
Isaku Yamahata, and with my further refinements.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 hw/acpi.c       |  293 ++++++++++++++++++++++++++++++++-----------------------
 qemu-options.hx |    7 +-
 2 files changed, 176 insertions(+), 124 deletions(-)
Isaku Yamahata - April 14, 2011, 1:50 a.m.
Ping.
Gleb, The issue of specifying both data and file is addressed.
Do you have any other comments? Otherwise can you provide your acked-by?

On Tue, Apr 05, 2011 at 10:53:16PM +0400, Michael Tokarev wrote:
> This patch almost rewrites acpi_table_add() function
> (but still leaves it using old get_param_value() interface).
> The result is that it's now possible to specify whole table
> (together with a header) in an external file, instead of just
> data portion, with a new file= parameter, but at the same time
> it's still possible to specify header fields as before.
> 
> Now with the checkpatch.pl formatting fixes, thanks to
> Stefan Hajnoczi for suggestions, with changes from
> Isaku Yamahata, and with my further refinements.
> 
> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
> ---
>  hw/acpi.c       |  293 ++++++++++++++++++++++++++++++++-----------------------
>  qemu-options.hx |    7 +-
>  2 files changed, 176 insertions(+), 124 deletions(-)
> 
> diff --git a/hw/acpi.c b/hw/acpi.c
> index 237526d..3def259 100644
> --- a/hw/acpi.c
> +++ b/hw/acpi.c
> @@ -15,6 +15,7 @@
>   * You should have received a copy of the GNU Lesser General Public
>   * License along with this library; if not, see <http://www.gnu.org/licenses/>
>   */
> +
>  #include "hw.h"
>  #include "pc.h"
>  #include "acpi.h"
> @@ -24,17 +25,29 @@
>  
>  struct acpi_table_header
>  {
> -    char signature [4];    /* ACPI signature (4 ASCII characters) */
> +    uint16_t _length;         /* our length, not actual part of the hdr */
> +                              /* XXX why we have 2 length fields here? */
> +    char sig[4];              /* ACPI signature (4 ASCII characters) */
>      uint32_t length;          /* Length of table, in bytes, including header */
>      uint8_t revision;         /* ACPI Specification minor version # */
>      uint8_t checksum;         /* To make sum of entire table == 0 */
> -    char oem_id [6];       /* OEM identification */
> -    char oem_table_id [8]; /* OEM table identification */
> +    char oem_id[6];           /* OEM identification */
> +    char oem_table_id[8];     /* OEM table identification */
>      uint32_t oem_revision;    /* OEM revision number */
> -    char asl_compiler_id [4]; /* ASL compiler vendor ID */
> +    char asl_compiler_id[4];  /* ASL compiler vendor ID */
>      uint32_t asl_compiler_revision; /* ASL compiler revision number */
>  } __attribute__((packed));
>  
> +#define ACPI_TABLE_HDR_SIZE sizeof(struct acpi_table_header)
> +#define ACPI_TABLE_PFX_SIZE sizeof(uint16_t)  /* size of the extra prefix */
> +
> +static const char dfl_hdr[ACPI_TABLE_HDR_SIZE] =
> +    "\0\0"                   /* fake _length (2) */
> +    "QEMU\0\0\0\0\1\0"       /* sig (4), len(4), revno (1), csum (1) */
> +    "QEMUQEQEMUQEMU\1\0\0\0" /* OEM id (6), table (8), revno (4) */
> +    "QEMU\1\0\0\0"           /* ASL compiler ID (4), version (4) */
> +    ;
> +
>  char *acpi_tables;
>  size_t acpi_tables_len;
>  
> @@ -47,156 +60,190 @@ static int acpi_checksum(const uint8_t *data, int len)
>      return (-sum) & 0xff;
>  }
>  
> +/* like strncpy() but zero-fills the tail of destination */
> +static void strzcpy(char *dst, const char *src, size_t size)
> +{
> +    size_t len = strlen(src);
> +    if (len >= size) {
> +        len = size;
> +    } else {
> +      memset(dst + len, 0, size - len);
> +    }
> +    memcpy(dst, src, len);
> +}
> +
> +/* XXX fixme: this function uses obsolete argument parsing interface */
>  int acpi_table_add(const char *t)
>  {
> -    static const char *dfl_id = "QEMUQEMU";
>      char buf[1024], *p, *f;
> -    struct acpi_table_header acpi_hdr;
>      unsigned long val;
> -    uint32_t length;
> -    struct acpi_table_header *acpi_hdr_p;
> -    size_t off;
> +    size_t len, start, allen;
> +    bool has_header;
> +    int changed;
> +    int r;
> +    struct acpi_table_header hdr;
> +
> +    r = 0;
> +    r |= get_param_value(buf, sizeof(buf), "data", t) ? 1 : 0;
> +    r |= get_param_value(buf, sizeof(buf), "file", t) ? 2 : 0;
> +    switch (r) {
> +    case 0:
> +        buf[0] = '\0';
> +    case 1:
> +        has_header = false;
> +        break;
> +    case 2:
> +        has_header = true;
> +        break;
> +    default:
> +        fprintf(stderr, "acpitable: both data and file are specified\n");
> +        return -1;
> +    }
> +
> +    if (!acpi_tables) {
> +        allen = sizeof(uint16_t);
> +        acpi_tables = qemu_mallocz(allen);
> +    }
> +    else {
> +        allen = acpi_tables_len;
> +    }
> +
> +    start = allen;
> +    acpi_tables = qemu_realloc(acpi_tables, start + ACPI_TABLE_HDR_SIZE);
> +    allen += has_header ? ACPI_TABLE_PFX_SIZE : ACPI_TABLE_HDR_SIZE;
> +
> +    /* now read in the data files, reallocating buffer as needed */
> +
> +    for (f = strtok(buf, ":"); f; f = strtok(NULL, ":")) {
> +        int fd = open(f, O_RDONLY);
> +
> +        if (fd < 0) {
> +            fprintf(stderr, "can't open file %s: %s\n", f, strerror(errno));
> +            return -1;
> +        }
> +
> +        for (;;) {
> +            char data[8192];
> +            r = read(fd, data, sizeof(data));
> +            if (r == 0) {
> +                break;
> +            } else if (r > 0) {
> +                acpi_tables = qemu_realloc(acpi_tables, allen + r);
> +                memcpy(acpi_tables + allen, data, r);
> +                allen += r;
> +            } else if (errno != EINTR) {
> +                fprintf(stderr, "can't read file %s: %s\n",
> +                        f, strerror(errno));
> +                close(fd);
> +                return -1;
> +            }
> +        }
> +
> +        close(fd);
> +    }
> +
> +    /* now fill in the header fields */
> +
> +    f = acpi_tables + start;   /* start of the table */
> +    changed = 0;
> +
> +    /* copy the header to temp place to align the fields */
> +    memcpy(&hdr, has_header ? f : dfl_hdr, ACPI_TABLE_HDR_SIZE);
> +
> +    /* length of the table minus our prefix */
> +    len = allen - start - ACPI_TABLE_PFX_SIZE;
> +
> +    hdr._length = cpu_to_le16(len);
>  
> -    memset(&acpi_hdr, 0, sizeof(acpi_hdr));
> -  
>      if (get_param_value(buf, sizeof(buf), "sig", t)) {
> -        strncpy(acpi_hdr.signature, buf, 4);
> -    } else {
> -        strncpy(acpi_hdr.signature, dfl_id, 4);
> +        strzcpy(hdr.sig, buf, sizeof(hdr.sig));
> +        ++changed;
> +    }
> +
> +    /* length of the table including header, in bytes */
> +    if (has_header) {
> +        /* check if actual length is correct */
> +        val = le32_to_cpu(hdr.length);
> +        if (val != len) {
> +            fprintf(stderr,
> +                "warning: acpitable has wrong length,"
> +                " header says %lu, actual size %u bytes\n",
> +                val, len);
> +            ++changed;
> +        }
>      }
> +    /* we may avoid putting length here if has_header is true */
> +    hdr.length = cpu_to_le32(len);
> +
>      if (get_param_value(buf, sizeof(buf), "rev", t)) {
> -        val = strtoul(buf, &p, 10);
> -        if (val > 255 || *p != '\0')
> -            goto out;
> -    } else {
> -        val = 1;
> +        val = strtoul(buf, &p, 0);
> +        if (val > 255 || *p) {
> +            fprintf(stderr, "acpitable: \"rev=%s\" is invalid\n", buf);
> +            return -1;
> +        }
> +        hdr.revision = (uint8_t)val;
> +        ++changed;
>      }
> -    acpi_hdr.revision = (int8_t)val;
>  
>      if (get_param_value(buf, sizeof(buf), "oem_id", t)) {
> -        strncpy(acpi_hdr.oem_id, buf, 6);
> -    } else {
> -        strncpy(acpi_hdr.oem_id, dfl_id, 6);
> +        strzcpy(hdr.oem_id, buf, sizeof(hdr.oem_id));
> +        ++changed;
>      }
>  
>      if (get_param_value(buf, sizeof(buf), "oem_table_id", t)) {
> -        strncpy(acpi_hdr.oem_table_id, buf, 8);
> -    } else {
> -        strncpy(acpi_hdr.oem_table_id, dfl_id, 8);
> +        strzcpy(hdr.oem_table_id, buf, sizeof(hdr.oem_table_id));
> +        ++changed;
>      }
>  
>      if (get_param_value(buf, sizeof(buf), "oem_rev", t)) {
> -        val = strtol(buf, &p, 10);
> -        if(*p != '\0')
> -            goto out;
> -    } else {
> -        val = 1;
> +        val = strtol(buf, &p, 0);
> +        if (*p) {
> +            fprintf(stderr, "acpitable: \"oem_rev=%s\" is invalid\n", buf);
> +            return -1;
> +        }
> +        hdr.oem_revision = cpu_to_le32(val);
> +        ++changed;
>      }
> -    acpi_hdr.oem_revision = cpu_to_le32(val);
>  
>      if (get_param_value(buf, sizeof(buf), "asl_compiler_id", t)) {
> -        strncpy(acpi_hdr.asl_compiler_id, buf, 4);
> -    } else {
> -        strncpy(acpi_hdr.asl_compiler_id, dfl_id, 4);
> +        strzcpy(hdr.asl_compiler_id, buf, sizeof(hdr.asl_compiler_id));
> +        ++changed;
>      }
>  
>      if (get_param_value(buf, sizeof(buf), "asl_compiler_rev", t)) {
> -        val = strtol(buf, &p, 10);
> -        if(*p != '\0')
> -            goto out;
> -    } else {
> -        val = 1;
> -    }
> -    acpi_hdr.asl_compiler_revision = cpu_to_le32(val);
> -    
> -    if (!get_param_value(buf, sizeof(buf), "data", t)) {
> -         buf[0] = '\0';
> -    }
> -
> -    length = sizeof(acpi_hdr);
> -
> -    f = buf;
> -    while (buf[0]) {
> -        struct stat s;
> -        char *n = strchr(f, ':');
> -        if (n)
> -            *n = '\0';
> -        if(stat(f, &s) < 0) {
> -            fprintf(stderr, "Can't stat file '%s': %s\n", f, strerror(errno));
> -            goto out;
> +        val = strtol(buf, &p, 0);
> +        if (*p) {
> +            fprintf(stderr, "acpitable: \"%s=%s\" is invalid\n",
> +                    "asl_compiler_rev", buf);
> +            return -1;
>          }
> -        length += s.st_size;
> -        if (!n)
> -            break;
> -        *n = ':';
> -        f = n + 1;
> +        hdr.asl_compiler_revision = cpu_to_le32(val);
> +        ++changed;
>      }
>  
> -    if (!acpi_tables) {
> -        acpi_tables_len = sizeof(uint16_t);
> -        acpi_tables = qemu_mallocz(acpi_tables_len);
> +    if (!has_header && !changed) {
> +        fprintf(stderr, "warning: acpitable: no table headers are specified\n");
>      }
> -    acpi_tables = qemu_realloc(acpi_tables,
> -                               acpi_tables_len + sizeof(uint16_t) + length);
> -    p = acpi_tables + acpi_tables_len;
> -    acpi_tables_len += sizeof(uint16_t) + length;
> -
> -    *(uint16_t*)p = cpu_to_le32(length);
> -    p += sizeof(uint16_t);
> -    memcpy(p, &acpi_hdr, sizeof(acpi_hdr));
> -    off = sizeof(acpi_hdr);
> -
> -    f = buf;
> -    while (buf[0]) {
> -        struct stat s;
> -        int fd;
> -        char *n = strchr(f, ':');
> -        if (n)
> -            *n = '\0';
> -        fd = open(f, O_RDONLY);
> -
> -        if(fd < 0)
> -            goto out;
> -        if(fstat(fd, &s) < 0) {
> -            close(fd);
> -            goto out;
> -        }
>  
> -        /* off < length is necessary because file size can be changed
> -           under our foot */
> -        while(s.st_size && off < length) {
> -            int r;
> -            r = read(fd, p + off, s.st_size);
> -            if (r > 0) {
> -                off += r;
> -                s.st_size -= r;
> -            } else if ((r < 0 && errno != EINTR) || r == 0) {
> -                close(fd);
> -                goto out;
> -            }
> -        }
>  
> -        close(fd);
> -        if (!n)
> -            break;
> -        f = n + 1;
> -    }
> -    if (off < length) {
> -        /* don't pass random value in process to guest */
> -        memset(p + off, 0, length - off);
> +    /* now calculate checksum of the table, complete with the header */
> +    /* we may as well leave checksum intact if has_header is true */
> +    /* alternatively there may be a way to set cksum to a given value */
> +    hdr.checksum = 0;    /* for checksum calculation */
> +
> +    /* put header back */
> +    memcpy(f, &hdr, sizeof(hdr));
> +
> +    if (changed || !has_header || 1) {
> +        ((struct acpi_table_header *)f)->checksum =
> +            acpi_checksum((uint8_t *)f + ACPI_TABLE_PFX_SIZE, len);
>      }
>  
> -    acpi_hdr_p = (struct acpi_table_header*)p;
> -    acpi_hdr_p->length = cpu_to_le32(length);
> -    acpi_hdr_p->checksum = acpi_checksum((uint8_t*)p, length);
>      /* increase number of tables */
> -    (*(uint16_t*)acpi_tables) =
> -	    cpu_to_le32(le32_to_cpu(*(uint16_t*)acpi_tables) + 1);
> +    (*(uint16_t *)acpi_tables) =
> +        cpu_to_le32(le32_to_cpu(*(uint16_t *)acpi_tables) + 1);
> +
> +    acpi_tables_len = allen;
>      return 0;
> -out:
> -    if (acpi_tables) {
> -        qemu_free(acpi_tables);
> -        acpi_tables = NULL;
> -    }
> -    return -1;
> +
>  }
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 18f54d2..e1d26b4 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -995,12 +995,17 @@ Enable virtio balloon device (default), optionally with PCI address
>  ETEXI
>  
>  DEF("acpitable", HAS_ARG, QEMU_OPTION_acpitable,
> -    "-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n][,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...]\n"
> +    "-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n][,asl_compiler_id=str][,asl_compiler_rev=n][,{data|file}=file1[:file2]...]\n"
>      "                ACPI table description\n", QEMU_ARCH_I386)
>  STEXI
>  @item -acpitable [sig=@var{str}][,rev=@var{n}][,oem_id=@var{str}][,oem_table_id=@var{str}][,oem_rev=@var{n}] [,asl_compiler_id=@var{str}][,asl_compiler_rev=@var{n}][,data=@var{file1}[:@var{file2}]...]
>  @findex -acpitable
>  Add ACPI table with specified header fields and context from specified files.
> +For file=, take whole ACPI table from the specified files, including all
> +ACPI headers (possible overridden by other options).
> +For data=, only data
> +portion of the table is used, all header information is specified in the
> +command line.
>  ETEXI
>  
>  DEF("smbios", HAS_ARG, QEMU_OPTION_smbios,
> -- 
> 1.7.2.5
> 
>

Patch

diff --git a/hw/acpi.c b/hw/acpi.c
index 237526d..3def259 100644
--- a/hw/acpi.c
+++ b/hw/acpi.c
@@ -15,6 +15,7 @@ 
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, see <http://www.gnu.org/licenses/>
  */
+
 #include "hw.h"
 #include "pc.h"
 #include "acpi.h"
@@ -24,17 +25,29 @@ 
 
 struct acpi_table_header
 {
-    char signature [4];    /* ACPI signature (4 ASCII characters) */
+    uint16_t _length;         /* our length, not actual part of the hdr */
+                              /* XXX why we have 2 length fields here? */
+    char sig[4];              /* ACPI signature (4 ASCII characters) */
     uint32_t length;          /* Length of table, in bytes, including header */
     uint8_t revision;         /* ACPI Specification minor version # */
     uint8_t checksum;         /* To make sum of entire table == 0 */
-    char oem_id [6];       /* OEM identification */
-    char oem_table_id [8]; /* OEM table identification */
+    char oem_id[6];           /* OEM identification */
+    char oem_table_id[8];     /* OEM table identification */
     uint32_t oem_revision;    /* OEM revision number */
-    char asl_compiler_id [4]; /* ASL compiler vendor ID */
+    char asl_compiler_id[4];  /* ASL compiler vendor ID */
     uint32_t asl_compiler_revision; /* ASL compiler revision number */
 } __attribute__((packed));
 
+#define ACPI_TABLE_HDR_SIZE sizeof(struct acpi_table_header)
+#define ACPI_TABLE_PFX_SIZE sizeof(uint16_t)  /* size of the extra prefix */
+
+static const char dfl_hdr[ACPI_TABLE_HDR_SIZE] =
+    "\0\0"                   /* fake _length (2) */
+    "QEMU\0\0\0\0\1\0"       /* sig (4), len(4), revno (1), csum (1) */
+    "QEMUQEQEMUQEMU\1\0\0\0" /* OEM id (6), table (8), revno (4) */
+    "QEMU\1\0\0\0"           /* ASL compiler ID (4), version (4) */
+    ;
+
 char *acpi_tables;
 size_t acpi_tables_len;
 
@@ -47,156 +60,190 @@  static int acpi_checksum(const uint8_t *data, int len)
     return (-sum) & 0xff;
 }
 
+/* like strncpy() but zero-fills the tail of destination */
+static void strzcpy(char *dst, const char *src, size_t size)
+{
+    size_t len = strlen(src);
+    if (len >= size) {
+        len = size;
+    } else {
+      memset(dst + len, 0, size - len);
+    }
+    memcpy(dst, src, len);
+}
+
+/* XXX fixme: this function uses obsolete argument parsing interface */
 int acpi_table_add(const char *t)
 {
-    static const char *dfl_id = "QEMUQEMU";
     char buf[1024], *p, *f;
-    struct acpi_table_header acpi_hdr;
     unsigned long val;
-    uint32_t length;
-    struct acpi_table_header *acpi_hdr_p;
-    size_t off;
+    size_t len, start, allen;
+    bool has_header;
+    int changed;
+    int r;
+    struct acpi_table_header hdr;
+
+    r = 0;
+    r |= get_param_value(buf, sizeof(buf), "data", t) ? 1 : 0;
+    r |= get_param_value(buf, sizeof(buf), "file", t) ? 2 : 0;
+    switch (r) {
+    case 0:
+        buf[0] = '\0';
+    case 1:
+        has_header = false;
+        break;
+    case 2:
+        has_header = true;
+        break;
+    default:
+        fprintf(stderr, "acpitable: both data and file are specified\n");
+        return -1;
+    }
+
+    if (!acpi_tables) {
+        allen = sizeof(uint16_t);
+        acpi_tables = qemu_mallocz(allen);
+    }
+    else {
+        allen = acpi_tables_len;
+    }
+
+    start = allen;
+    acpi_tables = qemu_realloc(acpi_tables, start + ACPI_TABLE_HDR_SIZE);
+    allen += has_header ? ACPI_TABLE_PFX_SIZE : ACPI_TABLE_HDR_SIZE;
+
+    /* now read in the data files, reallocating buffer as needed */
+
+    for (f = strtok(buf, ":"); f; f = strtok(NULL, ":")) {
+        int fd = open(f, O_RDONLY);
+
+        if (fd < 0) {
+            fprintf(stderr, "can't open file %s: %s\n", f, strerror(errno));
+            return -1;
+        }
+
+        for (;;) {
+            char data[8192];
+            r = read(fd, data, sizeof(data));
+            if (r == 0) {
+                break;
+            } else if (r > 0) {
+                acpi_tables = qemu_realloc(acpi_tables, allen + r);
+                memcpy(acpi_tables + allen, data, r);
+                allen += r;
+            } else if (errno != EINTR) {
+                fprintf(stderr, "can't read file %s: %s\n",
+                        f, strerror(errno));
+                close(fd);
+                return -1;
+            }
+        }
+
+        close(fd);
+    }
+
+    /* now fill in the header fields */
+
+    f = acpi_tables + start;   /* start of the table */
+    changed = 0;
+
+    /* copy the header to temp place to align the fields */
+    memcpy(&hdr, has_header ? f : dfl_hdr, ACPI_TABLE_HDR_SIZE);
+
+    /* length of the table minus our prefix */
+    len = allen - start - ACPI_TABLE_PFX_SIZE;
+
+    hdr._length = cpu_to_le16(len);
 
-    memset(&acpi_hdr, 0, sizeof(acpi_hdr));
-  
     if (get_param_value(buf, sizeof(buf), "sig", t)) {
-        strncpy(acpi_hdr.signature, buf, 4);
-    } else {
-        strncpy(acpi_hdr.signature, dfl_id, 4);
+        strzcpy(hdr.sig, buf, sizeof(hdr.sig));
+        ++changed;
+    }
+
+    /* length of the table including header, in bytes */
+    if (has_header) {
+        /* check if actual length is correct */
+        val = le32_to_cpu(hdr.length);
+        if (val != len) {
+            fprintf(stderr,
+                "warning: acpitable has wrong length,"
+                " header says %lu, actual size %u bytes\n",
+                val, len);
+            ++changed;
+        }
     }
+    /* we may avoid putting length here if has_header is true */
+    hdr.length = cpu_to_le32(len);
+
     if (get_param_value(buf, sizeof(buf), "rev", t)) {
-        val = strtoul(buf, &p, 10);
-        if (val > 255 || *p != '\0')
-            goto out;
-    } else {
-        val = 1;
+        val = strtoul(buf, &p, 0);
+        if (val > 255 || *p) {
+            fprintf(stderr, "acpitable: \"rev=%s\" is invalid\n", buf);
+            return -1;
+        }
+        hdr.revision = (uint8_t)val;
+        ++changed;
     }
-    acpi_hdr.revision = (int8_t)val;
 
     if (get_param_value(buf, sizeof(buf), "oem_id", t)) {
-        strncpy(acpi_hdr.oem_id, buf, 6);
-    } else {
-        strncpy(acpi_hdr.oem_id, dfl_id, 6);
+        strzcpy(hdr.oem_id, buf, sizeof(hdr.oem_id));
+        ++changed;
     }
 
     if (get_param_value(buf, sizeof(buf), "oem_table_id", t)) {
-        strncpy(acpi_hdr.oem_table_id, buf, 8);
-    } else {
-        strncpy(acpi_hdr.oem_table_id, dfl_id, 8);
+        strzcpy(hdr.oem_table_id, buf, sizeof(hdr.oem_table_id));
+        ++changed;
     }
 
     if (get_param_value(buf, sizeof(buf), "oem_rev", t)) {
-        val = strtol(buf, &p, 10);
-        if(*p != '\0')
-            goto out;
-    } else {
-        val = 1;
+        val = strtol(buf, &p, 0);
+        if (*p) {
+            fprintf(stderr, "acpitable: \"oem_rev=%s\" is invalid\n", buf);
+            return -1;
+        }
+        hdr.oem_revision = cpu_to_le32(val);
+        ++changed;
     }
-    acpi_hdr.oem_revision = cpu_to_le32(val);
 
     if (get_param_value(buf, sizeof(buf), "asl_compiler_id", t)) {
-        strncpy(acpi_hdr.asl_compiler_id, buf, 4);
-    } else {
-        strncpy(acpi_hdr.asl_compiler_id, dfl_id, 4);
+        strzcpy(hdr.asl_compiler_id, buf, sizeof(hdr.asl_compiler_id));
+        ++changed;
     }
 
     if (get_param_value(buf, sizeof(buf), "asl_compiler_rev", t)) {
-        val = strtol(buf, &p, 10);
-        if(*p != '\0')
-            goto out;
-    } else {
-        val = 1;
-    }
-    acpi_hdr.asl_compiler_revision = cpu_to_le32(val);
-    
-    if (!get_param_value(buf, sizeof(buf), "data", t)) {
-         buf[0] = '\0';
-    }
-
-    length = sizeof(acpi_hdr);
-
-    f = buf;
-    while (buf[0]) {
-        struct stat s;
-        char *n = strchr(f, ':');
-        if (n)
-            *n = '\0';
-        if(stat(f, &s) < 0) {
-            fprintf(stderr, "Can't stat file '%s': %s\n", f, strerror(errno));
-            goto out;
+        val = strtol(buf, &p, 0);
+        if (*p) {
+            fprintf(stderr, "acpitable: \"%s=%s\" is invalid\n",
+                    "asl_compiler_rev", buf);
+            return -1;
         }
-        length += s.st_size;
-        if (!n)
-            break;
-        *n = ':';
-        f = n + 1;
+        hdr.asl_compiler_revision = cpu_to_le32(val);
+        ++changed;
     }
 
-    if (!acpi_tables) {
-        acpi_tables_len = sizeof(uint16_t);
-        acpi_tables = qemu_mallocz(acpi_tables_len);
+    if (!has_header && !changed) {
+        fprintf(stderr, "warning: acpitable: no table headers are specified\n");
     }
-    acpi_tables = qemu_realloc(acpi_tables,
-                               acpi_tables_len + sizeof(uint16_t) + length);
-    p = acpi_tables + acpi_tables_len;
-    acpi_tables_len += sizeof(uint16_t) + length;
-
-    *(uint16_t*)p = cpu_to_le32(length);
-    p += sizeof(uint16_t);
-    memcpy(p, &acpi_hdr, sizeof(acpi_hdr));
-    off = sizeof(acpi_hdr);
-
-    f = buf;
-    while (buf[0]) {
-        struct stat s;
-        int fd;
-        char *n = strchr(f, ':');
-        if (n)
-            *n = '\0';
-        fd = open(f, O_RDONLY);
-
-        if(fd < 0)
-            goto out;
-        if(fstat(fd, &s) < 0) {
-            close(fd);
-            goto out;
-        }
 
-        /* off < length is necessary because file size can be changed
-           under our foot */
-        while(s.st_size && off < length) {
-            int r;
-            r = read(fd, p + off, s.st_size);
-            if (r > 0) {
-                off += r;
-                s.st_size -= r;
-            } else if ((r < 0 && errno != EINTR) || r == 0) {
-                close(fd);
-                goto out;
-            }
-        }
 
-        close(fd);
-        if (!n)
-            break;
-        f = n + 1;
-    }
-    if (off < length) {
-        /* don't pass random value in process to guest */
-        memset(p + off, 0, length - off);
+    /* now calculate checksum of the table, complete with the header */
+    /* we may as well leave checksum intact if has_header is true */
+    /* alternatively there may be a way to set cksum to a given value */
+    hdr.checksum = 0;    /* for checksum calculation */
+
+    /* put header back */
+    memcpy(f, &hdr, sizeof(hdr));
+
+    if (changed || !has_header || 1) {
+        ((struct acpi_table_header *)f)->checksum =
+            acpi_checksum((uint8_t *)f + ACPI_TABLE_PFX_SIZE, len);
     }
 
-    acpi_hdr_p = (struct acpi_table_header*)p;
-    acpi_hdr_p->length = cpu_to_le32(length);
-    acpi_hdr_p->checksum = acpi_checksum((uint8_t*)p, length);
     /* increase number of tables */
-    (*(uint16_t*)acpi_tables) =
-	    cpu_to_le32(le32_to_cpu(*(uint16_t*)acpi_tables) + 1);
+    (*(uint16_t *)acpi_tables) =
+        cpu_to_le32(le32_to_cpu(*(uint16_t *)acpi_tables) + 1);
+
+    acpi_tables_len = allen;
     return 0;
-out:
-    if (acpi_tables) {
-        qemu_free(acpi_tables);
-        acpi_tables = NULL;
-    }
-    return -1;
+
 }
diff --git a/qemu-options.hx b/qemu-options.hx
index 18f54d2..e1d26b4 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -995,12 +995,17 @@  Enable virtio balloon device (default), optionally with PCI address
 ETEXI
 
 DEF("acpitable", HAS_ARG, QEMU_OPTION_acpitable,
-    "-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n][,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...]\n"
+    "-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n][,asl_compiler_id=str][,asl_compiler_rev=n][,{data|file}=file1[:file2]...]\n"
     "                ACPI table description\n", QEMU_ARCH_I386)
 STEXI
 @item -acpitable [sig=@var{str}][,rev=@var{n}][,oem_id=@var{str}][,oem_table_id=@var{str}][,oem_rev=@var{n}] [,asl_compiler_id=@var{str}][,asl_compiler_rev=@var{n}][,data=@var{file1}[:@var{file2}]...]
 @findex -acpitable
 Add ACPI table with specified header fields and context from specified files.
+For file=, take whole ACPI table from the specified files, including all
+ACPI headers (possible overridden by other options).
+For data=, only data
+portion of the table is used, all header information is specified in the
+command line.
 ETEXI
 
 DEF("smbios", HAS_ARG, QEMU_OPTION_smbios,