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Elvira Khabirova 201766a20e ptrace: add PTRACE_GET_SYSCALL_INFO request 
PTRACE_GET_SYSCALL_INFO is a generic ptrace API that lets ptracer obtain
details of the syscall the tracee is blocked in.

There are two reasons for a special syscall-related ptrace request.

Firstly, with the current ptrace API there are cases when ptracer cannot
retrieve necessary information about syscalls.  Some examples include:

 * The notorious int-0x80-from-64-bit-task issue. See [1] for details.
   In short, if a 64-bit task performs a syscall through int 0x80, its
   tracer has no reliable means to find out that the syscall was, in
   fact, a compat syscall, and misidentifies it.

 * Syscall-enter-stop and syscall-exit-stop look the same for the
   tracer. Common practice is to keep track of the sequence of
   ptrace-stops in order not to mix the two syscall-stops up. But it is
   not as simple as it looks; for example, strace had a (just recently
   fixed) long-standing bug where attaching strace to a tracee that is
   performing the execve system call led to the tracer identifying the
   following syscall-exit-stop as syscall-enter-stop, which messed up
   all the state tracking.

 * Since the introduction of commit 84d77d3f06 ("ptrace: Don't allow
   accessing an undumpable mm"), both PTRACE_PEEKDATA and
   process_vm_readv become unavailable when the process dumpable flag is
   cleared. On such architectures as ia64 this results in all syscall
   arguments being unavailable for the tracer.

Secondly, ptracers also have to support a lot of arch-specific code for
obtaining information about the tracee.  For some architectures, this
requires a ptrace(PTRACE_PEEKUSER, ...) invocation for every syscall
argument and return value.

ptrace(2) man page:

long ptrace(enum __ptrace_request request, pid_t pid,
            void *addr, void *data);
...
PTRACE_GET_SYSCALL_INFO
       Retrieve information about the syscall that caused the stop.
       The information is placed into the buffer pointed by "data"
       argument, which should be a pointer to a buffer of type
       "struct ptrace_syscall_info".
       The "addr" argument contains the size of the buffer pointed to
       by "data" argument (i.e., sizeof(struct ptrace_syscall_info)).
       The return value contains the number of bytes available
       to be written by the kernel.
       If the size of data to be written by the kernel exceeds the size
       specified by "addr" argument, the output is truncated.

[ldv@altlinux.org: selftests/seccomp/seccomp_bpf: update for PTRACE_GET_SYSCALL_INFO]
  Link: http://lkml.kernel.org/r/20190708182904.GA12332@altlinux.org
Link: http://lkml.kernel.org/r/20190510152842.GF28558@altlinux.org
Signed-off-by: Elvira Khabirova <lineprinter@altlinux.org>
Co-developed-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Eugene Syromyatnikov <esyr@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Greentime Hu <greentime@andestech.com>
Cc: Helge Deller <deller@gmx.de>	[parisc]
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: kbuild test robot <lkp@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vincent Chen <deanbo422@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2019-07-16 19:23:24 -07:00
Documentation coda: change Coda's user api to use 64-bit time_t in timespec 2019-07-16 19:23:23 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch powerpc: define syscall_get_error() 2019-07-16 19:23:24 -07:00
block block: Limit zone array allocation size 2019-07-11 20:04:40 -06:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto USB / PHY patches for 5.3-rc1 2019-07-11 15:40:06 -07:00
drivers kernel: fix typos and some coding style in comments 2019-07-16 19:23:21 -07:00
fs fs/reiserfs/journal.c: change return type of dirty_one_transaction 2019-07-16 19:23:24 -07:00
include ptrace: add PTRACE_GET_SYSCALL_INFO request 2019-07-16 19:23:24 -07:00
init init/Kconfig: fix neighboring typos 2019-07-16 19:23:22 -07:00
ipc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
kernel ptrace: add PTRACE_GET_SYSCALL_INFO request 2019-07-16 19:23:24 -07:00
lib lib/rbtree: avoid generating code twice for the cached versions 2019-07-16 19:23:22 -07:00
mm mm: fix the MAP_UNINITIALIZED flag 2019-07-16 19:23:21 -07:00
net pci-v5.3-changes 2019-07-15 20:44:49 -07:00
samples Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
scripts checkpatch.pl: warn on duplicate sysctl local variable 2019-07-16 19:23:22 -07:00
security Merge branch 'akpm' (patches from Andrew) 2019-07-12 11:40:28 -07:00
sound kernel: fix typos and some coding style in comments 2019-07-16 19:23:21 -07:00
tools ptrace: add PTRACE_GET_SYSCALL_INFO request 2019-07-16 19:23:24 -07:00
usr kbuild: compile-test exported headers to ensure they are self-contained 2019-07-08 23:13:57 +09:00
virt ARM: 2019-07-12 15:35:14 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: do not create wrappers for header-test-y 2019-07-09 10:10:27 +09:00
.mailmap MAINTAINERS: Update my email address 2019-06-18 14:37:27 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-06-25 01:32:59 +02:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS for-linus-20190715 2019-07-15 21:20:52 -07:00
Makefile Kbuild updates for v5.3 2019-07-12 16:03:16 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.