Re: [PATCH v5 2/2] m68k: add kernel seccomp support

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Hi Geert,

I haven't been able to compile that one using the cross compiler:

m68k-linux-gnu-gcc -Wl,-no-as-needed -Wall  -lpthread seccomp_bpf.c  -o /usr/misc/m68k/linux-m68k-git/linux-m68k/tools/testing/selftests/seccomp/seccomp_bpf
seccomp_bpf.c: In function ‘user_notification_addfd’:
seccomp_bpf.c:3968:10: warning: implicit declaration of function ‘memfd_create’ [-Wimplicit-function-declaration]
  memfd = memfd_create("test", 0);
          ^
/tmp/ccfLGgXj.o: In function `user_notification_addfd':
seccomp_bpf.c:(.text+0x2ab32): undefined reference to `memfd_create'
/tmp/ccfLGgXj.o: In function `user_notification_addfd_rlimit':
seccomp_bpf.c:(.text+0x2c8a2): undefined reference to `memfd_create'
collect2: error: ld returned 1 exit status
../lib.mk:144: recipe for target '/usr/misc/m68k/linux-m68k-git/linux-m68k/tools/testing/selftests/seccomp/seccomp_bpf' failed

Adding the memfd_create definition found in tools/testing/selftests/drivers/dma-buf/udmabuf.c:

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 66f5145..231d772 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -266,6 +266,11 @@ struct seccomp_notif_addfd_big {
 #define SECCOMP_FILTER_FLAG_TSYNC_ESRCH (1UL << 4)
 #endif

+static int memfd_create(const char *name, unsigned int flags)
+{
+       return syscall(__NR_memfd_create, name, flags);
+}
+
 #ifndef seccomp
 int seccomp(unsigned int op, unsigned int flags, void *args)
 {

allows the tests to compile.

Running the test cases requires a fairly recent system - seccomp_bpf had 35 tests pass, 52 fail.

Cheers,

    Michael




On 23/06/21 7:35 pm, Geert Uytterhoeven wrote:
Hi Michael,

On Thu, Jun 17, 2021 at 7:39 AM Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
Add secure_computing() call to syscall_trace_enter to actually
filter system calls.

Add necessary arch Kconfig options, define TIF_SECCOMP trace
flag and provide basic seccomp filter support in asm/syscall.h

syscall_get_nr currently uses the syscall nr stored in orig_d0
because we change d0 to a default return code before starting a
syscall trace. This may be inconsistent with syscall_rollback
copying orig_d0 to d0 (which we never check upon return from
trace). We use d0 for the return code from syscall_trace_enter
in entry.S currently, and could perhaps expand that to store
a new syscall number returned by the seccomp filter before
executing the syscall. This clearly needs some discussion.

Compiles (for Atari) and boots on ARAnyM, otherwise untested.

Signed-off-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
---
  arch/m68k/Kconfig                   |  2 ++
  arch/m68k/include/asm/seccomp.h     | 11 +++++++++++
  arch/m68k/include/asm/syscall.h     | 33 +++++++++++++++++++++++++++++++++
  arch/m68k/include/asm/thread_info.h |  2 ++
  arch/m68k/kernel/ptrace.c           |  5 +++++
  5 files changed, 53 insertions(+)
  create mode 100644 arch/m68k/include/asm/seccomp.h

diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 372e4e6..deaea88 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -19,6 +19,8 @@ config M68K
         select GENERIC_STRNCPY_FROM_USER if MMU
         select GENERIC_STRNLEN_USER if MMU
         select HAVE_AOUT if MMU
+       select HAVE_ARCH_SECCOMP
+       select HAVE_ARCH_SECCOMP_FILTER
So the status should be changed from "TODO" to "ok" in
Documentation/features/seccomp/seccomp-filter/arch-support.txt

BTW, there was also "[PATCH] [WIP] selftests/seccomp: Add m68k support"
https://lore.kernel.org/linux-m68k/alpine.DEB.2.21.2008261315050.25325@xxxxxxxxxxxxxx/

I kept on up-porting it, but haven't exercised it recently.
Recent version looks like (gmail-whitespace-damaged):

--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -135,6 +135,8 @@ struct seccomp_data {
  #  define __NR_seccomp 337
  # elif defined(__sh__)
  #  define __NR_seccomp 372
+# elif defined(__mc68000__)
+#  define __NR_seccomp 380
  # else
  #  warning "seccomp syscall number unknown for this architecture"
  #  define __NR_seccomp 0xffff
@@ -1815,6 +1817,10 @@ TEST_F(TRACE_poke, getpid_runs_normally)
  # define ARCH_REGS             struct pt_regs
  # define SYSCALL_NUM(_regs)    (_regs).regs[3]
  # define SYSCALL_RET(_regs)    (_regs).regs[0]
+#elif defined(__mc68000__)
+# define ARCH_REGS             struct pt_regs
+# define SYSCALL_NUM(_regs)    (_regs).orig_d0
+# define SYSCALL_RET(_regs)    (_regs).d0
  #else
  # error "Do not know how to find your architecture's registers and syscalls"
  #endif
@@ -1879,7 +1885,7 @@ const bool ptrace_entry_set_syscall_ret =
   * Use PTRACE_GETREGS and PTRACE_SETREGS when available. This is useful for
   * architectures without HAVE_ARCH_TRACEHOOK (e.g. User-mode Linux).
   */
-#if defined(__x86_64__) || defined(__i386__) || defined(__mips__)
+#if defined(__x86_64__) || defined(__i386__) || defined(__mips__) ||
defined(__mc68000)
  # define ARCH_GETREGS(_regs)   ptrace(PTRACE_GETREGS, tracee, 0, &(_regs))
  # define ARCH_SETREGS(_regs)   ptrace(PTRACE_SETREGS, tracee, 0, &(_regs))
  #else

Gr{oetje,eeting}s,

                         Geert




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