From d6de73316412f133ac0d8011845b7667491e25a1 Mon Sep 17 00:00:00 2001 From: Ricardo Cañuelo Date: Mon, 8 Jun 2020 16:28:46 +0200 Subject: docs: more info about resources and the "enable_sysaclls" config option - Give some extra clarifications and examples about resources in syscall descriptions. - More details about how to use the "enable_syscalls" option. - Mention pseudo-syscalls in the general syscall description doc file. --- docs/syscall_descriptions_syntax.md | 33 ++++++++++++++++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) (limited to 'docs/syscall_descriptions_syntax.md') diff --git a/docs/syscall_descriptions_syntax.md b/docs/syscall_descriptions_syntax.md index 48ffcf380..39aa31437 100644 --- a/docs/syscall_descriptions_syntax.md +++ b/docs/syscall_descriptions_syntax.md @@ -149,7 +149,7 @@ Attributes are: ## Resources -Resources represent values that need to be passed from output of one syscall to input of another syscall. For example, `close` syscall requires an input value (fd) previously returned by `open` or `pipe` syscall. To achieve this, `fd` is declared as a resource. Resources are described as: +Resources represent values that need to be passed from output of one syscall to input of another syscall. For example, `close` syscall requires an input value (fd) previously returned by `open` or `pipe` syscall. To achieve this, `fd` is declared as a resource. This is a way of modelling dependencies between syscalls, as defining a syscall as the producer of a resource and another syscall as the consumer defines a loose sense of ordering between them. Resources are described as: ``` "resource" identifier "[" underlying_type "]" [ ":" const ("," const)* ] @@ -167,6 +167,31 @@ accept(fd sock, ...) sock listen(fd sock, backlog int32) ``` +Resources don't have to be necessarily returned by a syscall. They can be used as any other data type. For example: + +``` +resource fd_request[fd] + +ioctl$MEDIA_IOC_REQUEST_ALLOC(fd fd_media, cmd const[MEDIA_IOC_REQUEST_ALLOC], arg ptr[out, fd_request]) +ioctl$VIDIOC_QBUF(fd fd_video, cmd const[VIDIOC_QBUF], arg ptr[inout, v4l2_buffer]) + +v4l2_buffer { + index int32 + type flags[v4l2_buf_type, int32] + bytesused len[type, int32] + flags const[V4L2_BUF_FLAG_REQUEST_FD, int32] + field int32 + timestamp timeval + timecode v4l2_timecode + sequence int32 + memory flags[v4l2_memory, int32] + m v4l2_buffer_union + length int32 + reserved2 const[0, int32] + request_fd fd_request[opt] +} +``` + ## Type Aliases Complex types that are often repeated can be given short type aliases using the @@ -331,3 +356,9 @@ define MY_PATH_MAX PATH_MAX + 2 Description files also contain `include` directives that refer to Linux kernel header files, `incdir` directives that refer to custom Linux kernel header directories and `define` directives that define symbolic constant values. + +The syzkaller executor defines some pseudo sytem calls that can be used +as any other syscall in a description file. These pseudo system calls +expand to literal C code and can perform user-defined custom +actions. You can find some examples in +[executor/common_linux.h](../executor/common_linux.h). -- cgit mrf-deployment