This commit introduces the main infrastructure used for turning register
values into user-facing values that can be printed by strace. This
includes the ability to copy data from a particular memory address in
the traced process. On top of this, (partial) formatting has been added
for the most common I/O operations (open, read, write, lseek, close,
stat, fstat).
Moving the formatting of strace's output into a separate function will
allow us to introduce more complexity into the formatting logic without
touching the main body of the program.
The new function uses a switch statement to select how to format the
arguments and result depending on the syscall. At this point we only
include the default formatting, where the registers are simply dumped,
but later on we can add specializations for each system call we want to
support.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
This achieves two things:
- Programs can now intentionally perform arbitrary syscalls by calling
syscall(). This allows us to work on things like syscall fuzzing.
- It restricts the ability of userspace to make syscalls to a single
4KB page of code. In order to call the kernel directly, an attacker
must now locate this page and call through it.
