Re: [Regression] Build failure in current mainline - firmware related

On Sat, Jan 03, 2009 at 10:43:28PM +0100, Rafael J. Wysocki wrote:
On Saturday 03 January 2009, Sam Ravnborg wrote:
On Sat, Jan 03, 2009 at 09:49:48PM +0100, Sam Ravnborg wrote:
On Sat, Jan 03, 2009 at 12:47:14PM +0100, Rafael J. Wysocki wrote:
Hi,

I get the following error from 'make modules_install' on my test boxes:

HOSTCC firmware/ihex2fw
/home/rafael/src/linux-2.6/firmware/ihex2fw.c:268: fatal error: opening dependency file firmware/.ihex2fw.d: Read-only file system
compilation terminated.
make[3]: *** [firmware/ihex2fw] Error 1
make[2]: *** [_modinst_post] Error 2
make[1]: *** [sub-make] Error 2
make: *** [all] Error 2

where the configuration is that the kernel is compiled on a build box
with 'make O=<destdir> -j5' and then <destdir> is mounted over NFS read-only by
each test box (full path to this directory is the same on the build box and on
the test boxes). Then, I cd into <destdir>, run 'make modules_install' and get
the error above.

2.6.28 didn't have this problem.


Strange...
1) The string "opening dependency file" does not occur in my freshly pulled kernel
2) Line 268 is last line of ihex2fw.c

Could you try to do a "make modules_install V=1" to see the exact arguments supplied ti ihex2fw.c

I gave up on all the firmware stuff long time ago and has
never properly reviewed the implementation so I really
have no clue what is actually happening.

Walking through the 179 lines Makefile has not yet benn on my
"fun to do" list - and it most likely take a while before it hits it.

Took a quick peek. The Makefile uses "order only" in three spots.
This alone demand make version 3.80 IIRC and Documetnation/Changes
says 3.79.1...

The "order only" is so rare that Paul Smith once said that
coming up with a good example of usage was not easy.

For the headers_* stuff I recall when I reworked it I could
kill the usage of "order only" there but now it crept
back - sigh!

Well, in the meantime I ran 'make modules_install V=1' and this is the
last thing printed (the previous ones are not really interesting):

make -f /home/rafael/src/linux-2.6/scripts/Makefile.fwinst obj=firmware __fw_modinst
gcc -Wp,-MD,firmware/.ihex2fw.d -Ifirmware -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -o firmware/ihex2fw /home/rafael/src/linux-2.6/firmware/ihex2fw.c
/home/rafael/src/linux-2.6/firmware/ihex2fw.c:268: fatal error: opening dependency file firmware/.ihex2fw.d: Read-only file system
compilation terminated.
make[3]: *** [firmware/ihex2fw] Error 1
make[2]: *** [_modinst_post] Error 2
make[1]: *** [sub-make] Error 2
make: *** [all] Error 2

It fails because of the attempt to compile ihex2fw .

There are at least two obvious ways to fix this.

We could try to rearrange things so we do not trigger
the rebuild of ihex2fw in the modules_install case.
This would likely involve creating a new file listing
all the firmawre files and share it between firmware/Makefile
and scripts/Makefile.fwinst

We could also move ihex2fw to scripts so it is build
as part of the preparation for a kernel build.

Attched patch does the latter.
[I will update the changelog before I eventually commit it].

Sam

Patch is in old-style but the majority of the patch is the file move.

From f023a3d57e2b70a2d3d9ac4a484f1d337f2a02e3 Mon Sep 17 00:00:00 2001
From: Sam Ravnborg <sam@xxxxxxxxxxxx>
Date: Sun, 4 Jan 2009 22:38:21 +0100
Subject: [PATCH] kbuild: move ihex2fw to scripts

This fix a situation where we try to rebuild ihex2fw
when we do modules_install

Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
---
firmware/Makefile | 10 +-
firmware/ihex2fw.c | 268 ----------------------------------------------------
scripts/Makefile | 2 +
scripts/ihex2fw.c | 268 ++++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 274 insertions(+), 274 deletions(-)
delete mode 100644 firmware/ihex2fw.c
create mode 100644 scripts/ihex2fw.c

diff --git a/firmware/Makefile b/firmware/Makefile
index 6968388..0423c41 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -88,10 +88,10 @@ quiet_cmd_ihex = IHEX $@
cmd_ihex = $(OBJCOPY) -Iihex -Obinary $< $@

quiet_cmd_ihex2fw = IHEX2FW $@
- cmd_ihex2fw = $(objtree)/$(obj)/ihex2fw $< $@
+ cmd_ihex2fw = $(objtree)/scripts/ihex2fw $< $@

quiet_cmd_h16tofw = H16TOFW $@
- cmd_h16tofw = $(objtree)/$(obj)/ihex2fw -w $< $@
+ cmd_h16tofw = $(objtree)/scripts/ihex2fw -w $< $@

quiet_cmd_fwbin = MK_FW $@
cmd_fwbin = FWNAME="$(patsubst firmware/%.gen.S,%,$@)"; \
@@ -154,11 +154,11 @@ $(obj)/%: $(obj)/%.ihex | $(objtree)/$(obj)/$$(dir %)
# is actually meaningful, because the firmware has to be loaded in a certain
# order rather than as a single binary blob. Thus, we convert them into our
# more compact binary representation of ihex records (<linux/ihex.h>)
-$(obj)/%.fw: $(obj)/%.HEX $(obj)/ihex2fw | $(objtree)/$(obj)/$$(dir %)
+$(obj)/%.fw: $(obj)/%.HEX | $(objtree)/$(obj)/$$(dir %)
$(call cmd,ihex2fw)

# .H16 is our own modified form of Intel HEX, with 16-bit length for records.
-$(obj)/%.fw: $(obj)/%.H16 $(obj)/ihex2fw | $(objtree)/$(obj)/$$(dir %)
+$(obj)/%.fw: $(obj)/%.H16 | $(objtree)/$(obj)/$$(dir %)
$(call cmd,h16tofw)

$(firmware-dirs):
@@ -175,5 +175,3 @@ targets := $(fw-shipped-) $(patsubst $(obj)/%,%, \
# Without this, built-in.o won't be created when it's empty, and the
# final vmlinux link will fail.
obj-n := dummy
-
-hostprogs-y := ihex2fw
diff --git a/firmware/ihex2fw.c b/firmware/ihex2fw.c
deleted file mode 100644
index 8f7fdaa..0000000
--- a/firmware/ihex2fw.c
+++ /dev/null
@@ -1,268 +0,0 @@
-/*
- * Parser/loader for IHEX formatted data.
- *
- * Copyright © 2008 David Woodhouse <dwmw2@xxxxxxxxxxxxx>
- * Copyright © 2005 Jan Harkes <jaharkes@xxxxxxxxxx>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-
-#include <stdint.h>
-#include <arpa/inet.h>
-#include <stdio.h>
-#include <errno.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/mman.h>
-#include <fcntl.h>
-#include <string.h>
-#include <unistd.h>
-#include <stdlib.h>
-#define _GNU_SOURCE
-#include <getopt.h>
-
-
-struct ihex_binrec {
- struct ihex_binrec *next; /* not part of the real data structure */
- uint32_t addr;
- uint16_t len;
- uint8_t data[];
-};
-
-/**
- * nybble/hex are little helpers to parse hexadecimal numbers to a byte value
- **/
-static uint8_t nybble(const uint8_t n)
-{
- if (n >= '0' && n <= '9') return n - '0';
- else if (n >= 'A' && n <= 'F') return n - ('A' - 10);
- else if (n >= 'a' && n <= 'f') return n - ('a' - 10);
- return 0;
-}
-
-static uint8_t hex(const uint8_t *data, uint8_t *crc)
-{
- uint8_t val = (nybble(data[0]) << 4) | nybble(data[1]);
- *crc += val;
- return val;
-}
-
-static int process_ihex(uint8_t *data, ssize_t size);
-static void file_record(struct ihex_binrec *record);
-static int output_records(int outfd);
-
-static int sort_records = 0;
-static int wide_records = 0;
-
-int usage(void)
-{
- fprintf(stderr, "ihex2fw: Convert ihex files into binary "
- "representation for use by Linux kernel\n");
- fprintf(stderr, "usage: ihex2fw [<options>] <src.HEX> <dst.fw>\n");
- fprintf(stderr, " -w: wide records (16-bit length)\n");
- fprintf(stderr, " -s: sort records by address\n");
- return 1;
-}
-
-int main(int argc, char **argv)
-{
- int infd, outfd;
- struct stat st;
- uint8_t *data;
- int opt;
-
- while ((opt = getopt(argc, argv, "ws")) != -1) {
- switch (opt) {
- case 'w':
- wide_records = 1;
- break;
- case 's':
- sort_records = 1;
- break;
- default:
- return usage();
- }
- }
-
- if (optind + 2 != argc)
- return usage();
-
- if (!strcmp(argv[optind], "-"))
- infd = 0;
- else
- infd = open(argv[optind], O_RDONLY);
- if (infd == -1) {
- fprintf(stderr, "Failed to open source file: %s",
- strerror(errno));
- return usage();
- }
- if (fstat(infd, &st)) {
- perror("stat");
- return 1;
- }
- data = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, infd, 0);
- if (data == MAP_FAILED) {
- perror("mmap");
- return 1;
- }
-
- if (!strcmp(argv[optind+1], "-"))
- outfd = 1;
- else
- outfd = open(argv[optind+1], O_TRUNC|O_CREAT|O_WRONLY, 0644);
- if (outfd == -1) {
- fprintf(stderr, "Failed to open destination file: %s",
- strerror(errno));
- return usage();
- }
- if (process_ihex(data, st.st_size))
- return 1;
-
- output_records(outfd);
- return 0;
-}
-
-static int process_ihex(uint8_t *data, ssize_t size)
-{
- struct ihex_binrec *record;
- uint32_t offset = 0;
- uint8_t type, crc = 0, crcbyte = 0;
- int i, j;
- int line = 1;
- int len;
-
- i = 0;
-next_record:
- /* search for the start of record character */
- while (i < size) {
- if (data[i] == '\n') line++;
- if (data[i++] == ':') break;
- }
-
- /* Minimum record length would be about 10 characters */
- if (i + 10 > size) {
- fprintf(stderr, "Can't find valid record at line %d\n", line);
- return -EINVAL;
- }
-
- len = hex(data + i, &crc); i += 2;
- if (wide_records) {
- len <<= 8;
- len += hex(data + i, &crc); i += 2;
- }
- record = malloc((sizeof (*record) + len + 3) & ~3);
- if (!record) {
- fprintf(stderr, "out of memory for records\n");
- return -ENOMEM;
- }
- memset(record, 0, (sizeof(*record) + len + 3) & ~3);
- record->len = len;
-
- /* now check if we have enough data to read everything */
- if (i + 8 + (record->len * 2) > size) {
- fprintf(stderr, "Not enough data to read complete record at line %d\n",
- line);
- return -EINVAL;
- }
-
- record->addr = hex(data + i, &crc) << 8; i += 2;
- record->addr |= hex(data + i, &crc); i += 2;
- type = hex(data + i, &crc); i += 2;
-
- for (j = 0; j < record->len; j++, i += 2)
- record->data[j] = hex(data + i, &crc);
-
- /* check CRC */
- crcbyte = hex(data + i, &crc); i += 2;
- if (crc != 0) {
- fprintf(stderr, "CRC failure at line %d: got 0x%X, expected 0x%X\n",
- line, crcbyte, (unsigned char)(crcbyte-crc));
- return -EINVAL;
- }
-
- /* Done reading the record */
- switch (type) {
- case 0:
- /* old style EOF record? */
- if (!record->len)
- break;
-
- record->addr += offset;
- file_record(record);
- goto next_record;
-
- case 1: /* End-Of-File Record */
- if (record->addr || record->len) {
- fprintf(stderr, "Bad EOF record (type 01) format at line %d",
- line);
- return -EINVAL;
- }
- break;
-
- case 2: /* Extended Segment Address Record (HEX86) */
- case 4: /* Extended Linear Address Record (HEX386) */
- if (record->addr || record->len != 2) {
- fprintf(stderr, "Bad HEX86/HEX386 record (type %02X) at line %d\n",
- type, line);
- return -EINVAL;
- }
-
- /* We shouldn't really be using the offset for HEX86 because
- * the wraparound case is specified quite differently. */
- offset = record->data[0] << 8 | record->data[1];
- offset <<= (type == 2 ? 4 : 16);
- goto next_record;
-
- case 3: /* Start Segment Address Record */
- case 5: /* Start Linear Address Record */
- if (record->addr || record->len != 4) {
- fprintf(stderr, "Bad Start Address record (type %02X) at line %d\n",
- type, line);
- return -EINVAL;
- }
-
- /* These records contain the CS/IP or EIP where execution
- * starts. Don't really know what to do with them. */
- goto next_record;
-
- default:
- fprintf(stderr, "Unknown record (type %02X)\n", type);
- return -EINVAL;
- }
-
- return 0;
-}
-
-static struct ihex_binrec *records;
-
-static void file_record(struct ihex_binrec *record)
-{
- struct ihex_binrec **p = &records;
-
- while ((*p) && (!sort_records || (*p)->addr < record->addr))
- p = &((*p)->next);
-
- record->next = *p;
- *p = record;
-}
-
-static int output_records(int outfd)
-{
- unsigned char zeroes[6] = {0, 0, 0, 0, 0, 0};
- struct ihex_binrec *p = records;
-
- while (p) {
- uint16_t writelen = (p->len + 9) & ~3;
-
- p->addr = htonl(p->addr);
- p->len = htons(p->len);
- write(outfd, &p->addr, writelen);
- p = p->next;
- }
- /* EOF record is zero length, since we don't bother to represent
- the type field in the binary version */
- write(outfd, zeroes, 6);
- return 0;
-}
diff --git a/scripts/Makefile b/scripts/Makefile
index aafdf06..db5dd47 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -2,11 +2,13 @@
# scripts contains sources for various helper programs used throughout
# the kernel for the build process.
# ---------------------------------------------------------------------------
+# ihex2fw: Parser/loader for IHEX formatted data
# kallsyms: Find all symbols in vmlinux
# pnmttologo: Convert pnm files to logo files
# conmakehash: Create chartable
# conmakehash: Create arrays for initializing the kernel console tables

+hostprogs-y := ihex2fw
hostprogs-$(CONFIG_KALLSYMS) += kallsyms
hostprogs-$(CONFIG_LOGO) += pnmtologo
hostprogs-$(CONFIG_VT) += conmakehash
diff --git a/scripts/ihex2fw.c b/scripts/ihex2fw.c
new file mode 100644
index 0000000..8f7fdaa
--- /dev/null
+++ b/scripts/ihex2fw.c
@@ -0,0 +1,268 @@
+/*
+ * Parser/loader for IHEX formatted data.
+ *
+ * Copyright © 2008 David Woodhouse <dwmw2@xxxxxxxxxxxxx>
+ * Copyright © 2005 Jan Harkes <jaharkes@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <stdint.h>
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+#define _GNU_SOURCE
+#include <getopt.h>
+
+
+struct ihex_binrec {
+ struct ihex_binrec *next; /* not part of the real data structure */
+ uint32_t addr;
+ uint16_t len;
+ uint8_t data[];
+};
+
+/**
+ * nybble/hex are little helpers to parse hexadecimal numbers to a byte value
+ **/
+static uint8_t nybble(const uint8_t n)
+{
+ if (n >= '0' && n <= '9') return n - '0';
+ else if (n >= 'A' && n <= 'F') return n - ('A' - 10);
+ else if (n >= 'a' && n <= 'f') return n - ('a' - 10);
+ return 0;
+}
+
+static uint8_t hex(const uint8_t *data, uint8_t *crc)
+{
+ uint8_t val = (nybble(data[0]) << 4) | nybble(data[1]);
+ *crc += val;
+ return val;
+}
+
+static int process_ihex(uint8_t *data, ssize_t size);
+static void file_record(struct ihex_binrec *record);
+static int output_records(int outfd);
+
+static int sort_records = 0;
+static int wide_records = 0;
+
+int usage(void)
+{
+ fprintf(stderr, "ihex2fw: Convert ihex files into binary "
+ "representation for use by Linux kernel\n");
+ fprintf(stderr, "usage: ihex2fw [<options>] <src.HEX> <dst.fw>\n");
+ fprintf(stderr, " -w: wide records (16-bit length)\n");
+ fprintf(stderr, " -s: sort records by address\n");
+ return 1;
+}
+
+int main(int argc, char **argv)
+{
+ int infd, outfd;
+ struct stat st;
+ uint8_t *data;
+ int opt;
+
+ while ((opt = getopt(argc, argv, "ws")) != -1) {
+ switch (opt) {
+ case 'w':
+ wide_records = 1;
+ break;
+ case 's':
+ sort_records = 1;
+ break;
+ default:
+ return usage();
+ }
+ }
+
+ if (optind + 2 != argc)
+ return usage();
+
+ if (!strcmp(argv[optind], "-"))
+ infd = 0;
+ else
+ infd = open(argv[optind], O_RDONLY);
+ if (infd == -1) {
+ fprintf(stderr, "Failed to open source file: %s",
+ strerror(errno));
+ return usage();
+ }
+ if (fstat(infd, &st)) {
+ perror("stat");
+ return 1;
+ }
+ data = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, infd, 0);
+ if (data == MAP_FAILED) {
+ perror("mmap");
+ return 1;
+ }
+
+ if (!strcmp(argv[optind+1], "-"))
+ outfd = 1;
+ else
+ outfd = open(argv[optind+1], O_TRUNC|O_CREAT|O_WRONLY, 0644);
+ if (outfd == -1) {
+ fprintf(stderr, "Failed to open destination file: %s",
+ strerror(errno));
+ return usage();
+ }
+ if (process_ihex(data, st.st_size))
+ return 1;
+
+ output_records(outfd);
+ return 0;
+}
+
+static int process_ihex(uint8_t *data, ssize_t size)
+{
+ struct ihex_binrec *record;
+ uint32_t offset = 0;
+ uint8_t type, crc = 0, crcbyte = 0;
+ int i, j;
+ int line = 1;
+ int len;
+
+ i = 0;
+next_record:
+ /* search for the start of record character */
+ while (i < size) {
+ if (data[i] == '\n') line++;
+ if (data[i++] == ':') break;
+ }
+
+ /* Minimum record length would be about 10 characters */
+ if (i + 10 > size) {
+ fprintf(stderr, "Can't find valid record at line %d\n", line);
+ return -EINVAL;
+ }
+
+ len = hex(data + i, &crc); i += 2;
+ if (wide_records) {
+ len <<= 8;
+ len += hex(data + i, &crc); i += 2;
+ }
+ record = malloc((sizeof (*record) + len + 3) & ~3);
+ if (!record) {
+ fprintf(stderr, "out of memory for records\n");
+ return -ENOMEM;
+ }
+ memset(record, 0, (sizeof(*record) + len + 3) & ~3);
+ record->len = len;
+
+ /* now check if we have enough data to read everything */
+ if (i + 8 + (record->len * 2) > size) {
+ fprintf(stderr, "Not enough data to read complete record at line %d\n",
+ line);
+ return -EINVAL;
+ }
+
+ record->addr = hex(data + i, &crc) << 8; i += 2;
+ record->addr |= hex(data + i, &crc); i += 2;
+ type = hex(data + i, &crc); i += 2;
+
+ for (j = 0; j < record->len; j++, i += 2)
+ record->data[j] = hex(data + i, &crc);
+
+ /* check CRC */
+ crcbyte = hex(data + i, &crc); i += 2;
+ if (crc != 0) {
+ fprintf(stderr, "CRC failure at line %d: got 0x%X, expected 0x%X\n",
+ line, crcbyte, (unsigned char)(crcbyte-crc));
+ return -EINVAL;
+ }
+
+ /* Done reading the record */
+ switch (type) {
+ case 0:
+ /* old style EOF record? */
+ if (!record->len)
+ break;
+
+ record->addr += offset;
+ file_record(record);
+ goto next_record;
+
+ case 1: /* End-Of-File Record */
+ if (record->addr || record->len) {
+ fprintf(stderr, "Bad EOF record (type 01) format at line %d",
+ line);
+ return -EINVAL;
+ }
+ break;
+
+ case 2: /* Extended Segment Address Record (HEX86) */
+ case 4: /* Extended Linear Address Record (HEX386) */
+ if (record->addr || record->len != 2) {
+ fprintf(stderr, "Bad HEX86/HEX386 record (type %02X) at line %d\n",
+ type, line);
+ return -EINVAL;
+ }
+
+ /* We shouldn't really be using the offset for HEX86 because
+ * the wraparound case is specified quite differently. */
+ offset = record->data[0] << 8 | record->data[1];
+ offset <<= (type == 2 ? 4 : 16);
+ goto next_record;
+
+ case 3: /* Start Segment Address Record */
+ case 5: /* Start Linear Address Record */
+ if (record->addr || record->len != 4) {
+ fprintf(stderr, "Bad Start Address record (type %02X) at line %d\n",
+ type, line);
+ return -EINVAL;
+ }
+
+ /* These records contain the CS/IP or EIP where execution
+ * starts. Don't really know what to do with them. */
+ goto next_record;
+
+ default:
+ fprintf(stderr, "Unknown record (type %02X)\n", type);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static struct ihex_binrec *records;
+
+static void file_record(struct ihex_binrec *record)
+{
+ struct ihex_binrec **p = &records;
+
+ while ((*p) && (!sort_records || (*p)->addr < record->addr))
+ p = &((*p)->next);
+
+ record->next = *p;
+ *p = record;
+}
+
+static int output_records(int outfd)
+{
+ unsigned char zeroes[6] = {0, 0, 0, 0, 0, 0};
+ struct ihex_binrec *p = records;
+
+ while (p) {
+ uint16_t writelen = (p->len + 9) & ~3;
+
+ p->addr = htonl(p->addr);
+ p->len = htons(p->len);
+ write(outfd, &p->addr, writelen);
+ p = p->next;
+ }
+ /* EOF record is zero length, since we don't bother to represent
+ the type field in the binary version */
+ write(outfd, zeroes, 6);
+ return 0;
+}
--
1.6.0.2.GIT



Thanks,
Rafael
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages

  • Re: [Regression] Build failure in current mainline - firmware related
    ... I get the following error from 'make modules_install' on my test boxes: ... The string "opening dependency file" does not occur in my freshly pulled kernel ... compilation terminated. ... It fails because of the attempt to compile ihex2fw. ...
    (Linux-Kernel)
  • [Git pull] x86 update
    ... x86 boot: document for 32 bit boot protocol ... +LinuxBIOS, etc, and kexec, the 16-bit real mode setup code in kernel ... int fix, num; ...
    (Linux-Kernel)
  • [PATCH] driver-core: devtmpfs - driver core maintained /dev tmpfs
    ... Subject: driver-core: devtmpfs - driver core maintained /dev tmpfs ... Devtmpfs lets the kernel create a tmpfs very early at kernel ... already existing kernel-created device node and use it. ... static int __init bsg_init ...
    (Linux-Kernel)
  • Re: 2.6.8.1-mm3
    ... > Kernel hacking is not an end in itself, ... > of compilation of any software as a benchmark are showstopping issues. ... benchmarks have to be useful to evaluate different ... Bundle a toolchain and all supporting userspace required for it ...
    (Linux-Kernel)
  • [NT] Multiple Windows XP Kernel Vulnerability Allow User Mode Programs To Gain Kernel Privileges
    ... Kernel Privileges ... entry with a pointer to your code and execute an INT n instruction. ... DWORD NotUsed; // Never accessed by the kernel ... mov ecx,esp ...
    (Securiteam)