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Subject[PATCH v6 3/3] Documentation: prctl/seccomp_filter
Date
Documents how system call filtering using Berkeley Packet
Filter programs works and how it may be used.
Includes an example for x86 (32-bit) and a semi-generic
example using an example code generator.

v6: - tweak the language to note the requirement of
PR_SET_NO_NEW_PRIVS being called prior to use. (luto@mit.edu)
v5: - update sample to use system call arguments
- adds a "fancy" example using a macro-based generator
- cleaned up bpf in the sample
- update docs to mention arguments
- fix prctl value (eparis@redhat.com)
- language cleanup (rdunlap@xenotime.net)
v4: - update for no_new_privs use
- minor tweaks
v3: - call out BPF <-> Berkeley Packet Filter (rdunlap@xenotime.net)
- document use of tentative always-unprivileged
- guard sample compilation for i386 and x86_64
v2: - move code to samples (corbet@lwn.net)

Signed-off-by: Will Drewry <wad@chromium.org>
---
Documentation/prctl/seccomp_filter.txt | 100 +++++++++++++++
samples/Makefile | 2 +-
samples/seccomp/Makefile | 27 ++++
samples/seccomp/bpf-direct.c | 77 +++++++++++
samples/seccomp/bpf-fancy.c | 95 ++++++++++++++
samples/seccomp/bpf-helper.c | 89 +++++++++++++
samples/seccomp/bpf-helper.h | 219 ++++++++++++++++++++++++++++++++
7 files changed, 608 insertions(+), 1 deletions(-)
create mode 100644 Documentation/prctl/seccomp_filter.txt
create mode 100644 samples/seccomp/Makefile
create mode 100644 samples/seccomp/bpf-direct.c
create mode 100644 samples/seccomp/bpf-fancy.c
create mode 100644 samples/seccomp/bpf-helper.c
create mode 100644 samples/seccomp/bpf-helper.h
diff --git a/Documentation/prctl/seccomp_filter.txt b/Documentation/prctl/seccomp_filter.txt
new file mode 100644
index 0000000..4ad7649
--- /dev/null
+++ b/Documentation/prctl/seccomp_filter.txt
@@ -0,0 +1,100 @@
+ Seccomp filtering
+ =================
+
+Introduction
+------------
+
+A large number of system calls are exposed to every userland process
+with many of them going unused for the entire lifetime of the process.
+As system calls change and mature, bugs are found and eradicated. A
+certain subset of userland applications benefit by having a reduced set
+of available system calls. The resulting set reduces the total kernel
+surface exposed to the application. System call filtering is meant for
+use with those applications.
+
+Seccomp filtering provides a means for a process to specify a filter for
+incoming system calls. The filter is expressed as a Berkeley Packet
+Filter (BPF) program, as with socket filters, except that the data
+operated on is related to the system call being made: system call
+number, and the system call arguments. This allows for expressive
+filtering of system calls using a filter program language with a long
+history of being exposed to userland and a straightforward data set.
+
+Additionally, BPF makes it impossible for users of seccomp to fall prey
+to time-of-check-time-of-use (TOCTOU) attacks that are common in system
+call interposition frameworks. BPF programs may not dereference
+pointers which constrains all filters to solely evaluating the system
+call arguments directly.
+
+What it isn't
+-------------
+
+System call filtering isn't a sandbox. It provides a clearly defined
+mechanism for minimizing the exposed kernel surface. Beyond that,
+policy for logical behavior and information flow should be managed with
+a combination of other system hardening techniques and, potentially, an
+LSM of your choosing. Expressive, dynamic filters provide further options down
+this path (avoiding pathological sizes or selecting which of the multiplexed
+system calls in socketcall() is allowed, for instance) which could be
+construed, incorrectly, as a more complete sandboxing solution.
+
+Usage
+-----
+
+An additional seccomp mode is added, but they are not directly set by
+the consuming process. The new mode, '2', is only available if
+CONFIG_SECCOMP_FILTER is set and enabled using prctl with the
+PR_ATTACH_SECCOMP_FILTER argument.
+
+Interacting with seccomp filters is done using one prctl(2) call.
+
+PR_ATTACH_SECCOMP_FILTER:
+ Allows the specification of a new filter using a BPF program.
+ The BPF program will be executed over struct seccomp_filter_data
+ reflecting the system call number, arguments, and other
+ metadata, To allow a system call, SECCOMP_BPF_ALLOW must be
+ returned. At present, all other return values result in the
+ system call being blocked, but it is recommended to return
+ SECCOMP_BPF_DENY in those cases. This will allow for future
+ custom return values to be introduced, if ever desired.
+
+ Usage:
+ prctl(PR_ATTACH_SECCOMP_FILTER, prog);
+
+ The 'prog' argument is a pointer to a struct sock_fprog which will
+ contain the filter program. If the program is invalid, the call
+ will return -1 and set errno to EINVAL.
+
+ Note, is_compat_task is also tracked for the @prog. This means
+ that once set the calling task will have all of its system calls
+ blocked if it switches its system call ABI.
+
+ If fork/clone and execve are allowed by @prog, any child processes will
+ be constrained to the same filters and system call ABI as the parent.
+
+ Prior to use, the task must call prctl(PR_SET_NO_NEW_PRIVS, 1) or
+ run with CAP_SYS_ADMIN privileges in its namespace. If these are not
+ true, -EACCES will be returned. This requirement ensures that filter
+ programs cannot be applied to child processes with greater privileges
+ than the task that installed them.
+
+ Additionally, if prctl(2) is allowed by the attached filter,
+ additional filters may be layered on which will increase evaluation
+ time, but allow for further decreasing the attack surface during
+ execution of a process.
+
+The above call returns 0 on success and non-zero on error.
+
+Example
+-------
+
+The samples/seccomp/ directory contains both a 32-bit specific example
+and a more generic example of a higher level macro interface for BPF
+program generation.
+
+Adding architecture support
+-----------------------
+
+Any platform with seccomp support will support seccomp filters as long
+as CONFIG_SECCOMP_FILTER is enabled and the architecture has implemented
+syscall_get_arguments.
diff --git a/samples/Makefile b/samples/Makefile
index 6280817..f29b19c 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,4 +1,4 @@
# Makefile for Linux samples code

obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ tracepoints/ trace_events/ \
- hw_breakpoint/ kfifo/ kdb/ hidraw/
+ hw_breakpoint/ kfifo/ kdb/ hidraw/ seccomp/
diff --git a/samples/seccomp/Makefile b/samples/seccomp/Makefile
new file mode 100644
index 0000000..0298c6f
--- /dev/null
+++ b/samples/seccomp/Makefile
@@ -0,0 +1,27 @@
+# kbuild trick to avoid linker error. Can be omitted if a module is built.
+obj- := dummy.o
+
+hostprogs-y := bpf-fancy
+bpf-fancy-objs := bpf-fancy.o bpf-helper.o
+
+HOSTCFLAGS_bpf-fancy.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-fancy.o += -idirafter $(objtree)/include
+HOSTCFLAGS_bpf-helper.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-helper.o += -idirafter $(objtree)/include
+
+# bpf-direct.c is x86-only.
+ifeq ($(filter-out x86_64 i386,$(KBUILD_BUILDHOST)),)
+# List of programs to build
+hostprogs-y += bpf-direct
+bpf-direct-objs := bpf-direct.o
+endif
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
+
+HOSTCFLAGS_bpf-direct.o += -I$(objtree)/usr/include
+HOSTCFLAGS_bpf-direct.o += -idirafter $(objtree)/include
+ifeq ($(KBUILD_BUILDHOST),x86_64)
+HOSTCFLAGS_bpf-direct.o += -m32
+HOSTLOADLIBES_bpf-direct += -m32
+endif
diff --git a/samples/seccomp/bpf-direct.c b/samples/seccomp/bpf-direct.c
new file mode 100644
index 0000000..d799244
--- /dev/null
+++ b/samples/seccomp/bpf-direct.c
@@ -0,0 +1,77 @@
+/*
+ * 32-bit seccomp filter example with BPF macros
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <linux/filter.h>
+#include <linux/ptrace.h>
+#include <linux/seccomp_filter.h>
+#include <linux/unistd.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#ifndef PR_ATTACH_SECCOMP_FILTER
+# define PR_ATTACH_SECCOMP_FILTER 37
+#endif
+
+#define syscall_arg(_n) (offsetof(struct seccomp_filter_data, args[_n].lo32))
+#define nr (offsetof(struct seccomp_filter_data, syscall_nr))
+
+static int install_filter(void)
+{
+ struct seccomp_filter_block filter[] = {
+ /* Grab the system call number */
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, nr),
+ /* Jump table for the allowed syscalls */
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_rt_sigreturn, 10, 0),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_sigreturn, 9, 0),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit_group, 8, 0),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_exit, 7, 0),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_read, 1, 0),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_write, 2, 6),
+
+ /* Check that read is only using stdin. */
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 3, 4),
+
+ /* Check that write is only using stdout/stderr */
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDOUT_FILENO, 1, 0),
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDERR_FILENO, 0, 1),
+
+ BPF_STMT(BPF_RET+BPF_K, SECCOMP_BPF_ALLOW),
+ BPF_STMT(BPF_RET+BPF_K, SECCOMP_BPF_DENY),
+ };
+ struct seccomp_fprog prog = {
+ .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+ .filter = filter,
+ };
+ if (prctl(PR_ATTACH_SECCOMP_FILTER, &prog)) {
+ perror("prctl");
+ return 1;
+ }
+ return 0;
+}
+
+#define payload(_c) (_c), sizeof((_c))
+int main(int argc, char **argv)
+{
+ char buf[4096];
+ ssize_t bytes = 0;
+ if (install_filter())
+ return 1;
+ syscall(__NR_write, STDOUT_FILENO,
+ payload("OHAI! WHAT IS YOUR NAME? "));
+ bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf));
+ syscall(__NR_write, STDOUT_FILENO, payload("HELLO, "));
+ syscall(__NR_write, STDOUT_FILENO, buf, bytes);
+ return 0;
+}
diff --git a/samples/seccomp/bpf-fancy.c b/samples/seccomp/bpf-fancy.c
new file mode 100644
index 0000000..1318b1a
--- /dev/null
+++ b/samples/seccomp/bpf-fancy.c
@@ -0,0 +1,95 @@
+/*
+ * Seccomp BPF example using a macro-based generator.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <linux/seccomp_filter.h>
+#include <linux/unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "bpf-helper.h"
+
+#ifndef PR_ATTACH_SECCOMP_FILTER
+# define PR_ATTACH_SECCOMP_FILTER 37
+#endif
+
+int main(int argc, char **argv)
+{
+ struct bpf_labels l;
+ static const char msg1[] = "Please type something: ";
+ static const char msg2[] = "You typed: ";
+ char buf[256];
+ struct seccomp_filter_block filter[] = {
+ LOAD_SYSCALL_NR,
+ SYSCALL(__NR_exit, ALLOW),
+ SYSCALL(__NR_exit_group, ALLOW),
+ SYSCALL(__NR_write, JUMP(&l, write_fd)),
+ SYSCALL(__NR_read, JUMP(&l, read)),
+ DENY, /* Don't passthrough into a label */
+
+ LABEL(&l, read),
+ ARG(0),
+ JNE(STDIN_FILENO, DENY),
+ ARG(1),
+ JNE((unsigned long)buf, DENY),
+ ARG(2),
+ JGE(sizeof(buf), DENY),
+ ALLOW,
+
+ LABEL(&l, write_fd),
+ ARG(0),
+ JEQ(STDOUT_FILENO, JUMP(&l, write_buf)),
+ JEQ(STDERR_FILENO, JUMP(&l, write_buf)),
+ DENY,
+
+ LABEL(&l, write_buf),
+ ARG(1),
+ JEQ((unsigned long)msg1, JUMP(&l, msg1_len)),
+ JEQ((unsigned long)msg2, JUMP(&l, msg2_len)),
+ JEQ((unsigned long)buf, JUMP(&l, buf_len)),
+ DENY,
+
+ LABEL(&l, msg1_len),
+ ARG(2),
+ JLT(sizeof(msg1), ALLOW),
+ DENY,
+
+ LABEL(&l, msg2_len),
+ ARG(2),
+ JLT(sizeof(msg2), ALLOW),
+ DENY,
+
+ LABEL(&l, buf_len),
+ ARG(2),
+ JLT(sizeof(buf), ALLOW),
+ DENY,
+ };
+ struct seccomp_fprog prog = {
+ .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
+ .filter = filter,
+ };
+ ssize_t bytes;
+ bpf_resolve_jumps(&l, filter, sizeof(filter)/sizeof(*filter));
+
+ if (prctl(PR_ATTACH_SECCOMP_FILTER, &prog)) {
+ perror("prctl");
+ return 1;
+ }
+ syscall(__NR_write, STDOUT_FILENO, msg1, strlen(msg1));
+ bytes = syscall(__NR_read, STDIN_FILENO, buf, sizeof(buf)-1);
+ bytes = (bytes > 0 ? bytes : 0);
+ syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2));
+ syscall(__NR_write, STDERR_FILENO, buf, bytes);
+ /* Now get killed */
+ syscall(__NR_write, STDERR_FILENO, msg2, strlen(msg2)+2);
+ return 0;
+}
diff --git a/samples/seccomp/bpf-helper.c b/samples/seccomp/bpf-helper.c
new file mode 100644
index 0000000..e1b6bc7
--- /dev/null
+++ b/samples/seccomp/bpf-helper.c
@@ -0,0 +1,89 @@
+/*
+ * Seccomp BPF helper functions
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "bpf-helper.h"
+
+int bpf_resolve_jumps(struct bpf_labels *labels,
+ struct seccomp_filter_block *filter, size_t count)
+{
+ struct seccomp_filter_block *begin = filter;
+ __u8 insn = count - 1;
+
+ if (count < 1)
+ return -1;
+ /*
+ * Walk it once, backwards, to build the label table and do fixups.
+ * Since backward jumps are disallowed by BPF, this is easy.
+ */
+ filter += insn;
+ for (; filter >= begin; --insn, --filter) {
+ if (filter->code != (BPF_JMP+BPF_JA))
+ continue;
+ switch ((filter->jt<<8)|filter->jf) {
+ case (JUMP_JT<<8)|JUMP_JF:
+ if (labels->labels[filter->k].location == 0xffffffff) {
+ fprintf(stderr, "Unresolved label: '%s'\n",
+ labels->labels[filter->k].label);
+ return 1;
+ }
+ filter->k = labels->labels[filter->k].location -
+ (insn + 1);
+ filter->jt = 0;
+ filter->jf = 0;
+ continue;
+ case (LABEL_JT<<8)|LABEL_JF:
+ if (labels->labels[filter->k].location != 0xffffffff) {
+ fprintf(stderr, "Duplicate label use: '%s'\n",
+ labels->labels[filter->k].label);
+ return 1;
+ }
+ labels->labels[filter->k].location = insn;
+ filter->k = 0; /* fall through */
+ filter->jt = 0;
+ filter->jf = 0;
+ continue;
+ }
+ }
+ return 0;
+}
+
+/* Simple lookup table for labels. */
+__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label)
+{
+ struct __bpf_label *begin = labels->labels, *end;
+ int id;
+ if (labels->count == 0) {
+ begin->label = label;
+ begin->location = 0xffffffff;
+ labels->count++;
+ return 0;
+ }
+ end = begin + labels->count;
+ for (id = 0; begin < end; ++begin, ++id) {
+ if (!strcmp(label, begin->label))
+ return id;
+ }
+ begin->label = label;
+ begin->location = 0xffffffff;
+ labels->count++;
+ return id;
+}
+
+void seccomp_bpf_print(struct seccomp_filter_block *filter, size_t count)
+{
+ struct seccomp_filter_block *end = filter + count;
+ for ( ; filter < end; ++filter)
+ printf("{ code=%u,jt=%u,jf=%u,k=%u },\n",
+ filter->code, filter->jt, filter->jf, filter->k);
+}
diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h
new file mode 100644
index 0000000..92b94ec
--- /dev/null
+++ b/samples/seccomp/bpf-helper.h
@@ -0,0 +1,219 @@
+/*
+ * Example wrapper around BPF macros.
+ *
+ * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
+ * Author: Will Drewry <wad@chromium.org>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using prctl(PR_ATTACH_SECCOMP_FILTER).
+ *
+ * No guarantees are provided with respect to the correctness
+ * or functionality of this code.
+ */
+#ifndef __BPF_HELPER_H__
+#define __BPF_HELPER_H__
+
+#include <asm/bitsperlong.h> /* for __BITS_PER_LONG */
+#include <linux/filter.h>
+#include <linux/seccomp_filter.h> /* for seccomp_filter_data.arg */
+#include <linux/types.h>
+#include <linux/unistd.h>
+#include <stddef.h>
+
+#define BPF_LABELS_MAX 256
+struct bpf_labels {
+ int count;
+ struct __bpf_label {
+ const char *label;
+ __u32 location;
+ } labels[BPF_LABELS_MAX];
+};
+
+int bpf_resolve_jumps(struct bpf_labels *labels,
+ struct seccomp_filter_block *filter, size_t count);
+__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label);
+void seccomp_bpf_print(struct seccomp_filter_block *filter, size_t count);
+
+#define JUMP_JT 0xff
+#define JUMP_JF 0xff
+#define LABEL_JT 0xfe
+#define LABEL_JF 0xfe
+
+#define ALLOW \
+ BPF_STMT(BPF_RET+BPF_K, 0xFFFFFFFF)
+#define DENY \
+ BPF_STMT(BPF_RET+BPF_K, 0)
+#define JUMP(labels, label) \
+ BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
+ JUMP_JT, JUMP_JF)
+#define LABEL(labels, label) \
+ BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
+ LABEL_JT, LABEL_JF)
+#define SYSCALL(nr, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (nr), 0, 1), \
+ jt
+
+/* Lame, but just an example */
+#define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label)
+
+#define EXPAND(...) __VA_ARGS__
+/* Map all width-sensitive operations */
+#if __BITS_PER_LONG == 32
+
+#define JEQ(x, jt) JEQ32(x, EXPAND(jt))
+#define JNE(x, jt) JNE32(x, EXPAND(jt))
+#define JGT(x, jt) JGT32(x, EXPAND(jt))
+#define JLT(x, jt) JLT32(x, EXPAND(jt))
+#define JGE(x, jt) JGE32(x, EXPAND(jt))
+#define JLE(x, jt) JLE32(x, EXPAND(jt))
+#define JA(x, jt) JA32(x, EXPAND(jt))
+#define ARG(i) ARG_32(i)
+
+#elif __BITS_PER_LONG == 64
+
+#define JEQ(x, jt) \
+ JEQ64(((union seccomp_filter_arg){.u64 = (x)}).lo32, \
+ ((union seccomp_filter_arg){.u64 = (x)}).hi32, \
+ EXPAND(jt))
+#define JGT(x, jt) \
+ JGT64(((union seccomp_filter_arg){.u64 = (x)}).lo32, \
+ ((union seccomp_filter_arg){.u64 = (x)}).hi32, \
+ EXPAND(jt))
+#define JGE(x, jt) \
+ JGE64(((union seccomp_filter_arg){.u64 = (x)}).lo32, \
+ ((union seccomp_filter_arg){.u64 = (x)}).hi32, \
+ EXPAND(jt))
+#define JNE(x, jt) \
+ JNE64(((union seccomp_filter_arg){.u64 = (x)}).lo32, \
+ ((union seccomp_filter_arg){.u64 = (x)}).hi32, \
+ EXPAND(jt))
+#define JLT(x, jt) \
+ JLT64(((union seccomp_filter_arg){.u64 = (x)}).lo32, \
+ ((union seccomp_filter_arg){.u64 = (x)}).hi32, \
+ EXPAND(jt))
+#define JLE(x, jt) \
+ JLE64(((union seccomp_filter_arg){.u64 = (x)}).lo32, \
+ ((union seccomp_filter_arg){.u64 = (x)}).hi32, \
+ EXPAND(jt))
+
+#define JA(x, jt) \
+ JA64(((union seccomp_filter_arg){.u64 = (x)}).lo32, \
+ ((union seccomp_filter_arg){.u64 = (x)}).hi32, \
+ EXPAND(jt))
+#define ARG(i) ARG_64(i)
+
+#else
+#error __BITS_PER_LONG value unusable.
+#endif
+
+/* Loads the arg into A */
+#define ARG_32(idx) \
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+ offsetof(struct seccomp_filter_data, args[(idx)].lo32))
+
+/* Loads hi into A and lo in X */
+#define ARG_64(idx) \
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+ offsetof(struct seccomp_filter_data, args[(idx)].lo32)), \
+ BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+ offsetof(struct seccomp_filter_data, args[(idx)].hi32)), \
+ BPF_STMT(BPF_ST, 1) /* hi -> M[1] */
+
+#define JEQ32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \
+ jt
+
+#define JNE32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \
+ jt
+
+/* Checks the lo, then swaps to check the hi. A=lo,X=hi */
+#define JEQ64(lo, hi, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JNE64(lo, hi, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JA32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
+ jt
+
+#define JA64(lo, hi, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JGE32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
+ jt
+
+#define JLT32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
+ jt
+
+/* Shortcut checking if hi > arg.hi. */
+#define JGE64(lo, hi, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JLT64(lo, hi, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JGT32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
+ jt
+
+#define JLE32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
+ jt
+
+/* Check hi > args.hi first, then do the GE checking */
+#define JGT64(lo, hi, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define JLE64(lo, hi, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+
+#define LOAD_SYSCALL_NR \
+ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
+ offsetof(struct seccomp_filter_data, syscall_nr))
+
+#endif /* __BPF_HELPER_H__ */
--
1.7.5.4


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