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Implement initial userspace support #467

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Implement initial userspace support #467

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vijaydhanraj
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This is a draft PR that adds basic syscall support like exit, close, opendir, readdir and exec as well as init task and dm implementation. The purpose of this PR is to get feedback from the community and ensure the design aligns with principles of user-mode support described in https://github.com/coconut-svsm/svsm/blob/main/Documentation/docs/developer/DEVELOPMENT-PLAN.md as well syscall ABIs https://mail.8bytes.org/pipermail/svsm-devel/2024-June/000334.html.

PS: The changes are built on top of #456.

Freax13
Freax13 reviewed Sep 25, 2024
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Some preliminary review comments.

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@vijaydhanraj vijaydhanraj force-pushed the initial_userspace_support branch 3 times, most recently from d860c4a to a40bb5b Compare September 29, 2024 17:34
@vijaydhanraj
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Some preliminary review comments.

Thanks @Freax13 for the valuable comments. I have addressed all the earlier comments. Can you please take a look?

Freax13
Freax13 suggested changes Oct 4, 2024
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I don't have time for a full review right now, I'll do that sometime next week.

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Freax13 commented Oct 7, 2024

Now that #456 has been merged, this PR can be rebased onto main and probably be marked as "ready to review" (instead of as a draft).

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Now that #456 has been merged, this PR can be rebased onto main and probably be marked as "ready to review" (instead of as a draft).

Sure, will rebase, address your other comments and mark the PR ready to review.

@vijaydhanraj vijaydhanraj force-pushed the initial_userspace_support branch 2 times, most recently from 7493e6f to ac443c2 Compare October 9, 2024 05:52
@vijaydhanraj vijaydhanraj marked this pull request as ready for review October 9, 2024 05:56
Freax13
Freax13 reviewed Oct 9, 2024
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@vijaydhanraj vijaydhanraj mentioned this pull request Oct 13, 2024
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Freax13
Freax13 reviewed Oct 15, 2024
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Freax13 commented Oct 16, 2024

FYI this branch has conflicts with main. You might have to rebase your branch to resolve them.

Freax13
Freax13 reviewed Oct 16, 2024
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peterfang and others added 11 commits October 16, 2024 12:43
@peterfang @vijaydhanraj
syscall: Add Obj trait
52ab403 
Add a new trait, Obj, to ensure all of the object handles follow a
common interface. This helps with implementing common syscalls that can
be used for different object types.

Signed-off-by: Peter Fang <[email protected]>
@cxdong @vijaydhanraj
syscall: Rename numbers.rs to def.rs
dc58d9b 
Rename numbers.rs to def.rs so that this file can be extended in the
future to contain more definitions, like MMFlag, syscall error code
which are common for both kernel and user.

Signed-off-by: Chuanxiao Dong <[email protected]>
@cxdong @vijaydhanraj
kernel/syscall: Rename handlers.rs to class0.rs
2d6488c 
The syscall handlers in handlers.rs currently is for class0 so rename
the file to class0.rs. The plan is to introduce other syscall handlers
files for different classes.

Signed-off-by: Chuanxiao Dong <[email protected]>
@cxdong @vijaydhanraj
kernel/cpu/idt: Remove SYS_HELLO for implementing formal syscalls
3df76b1 
SYS_HELLO is a test syscall and occupies the syscall number 0, which is
for SYS_EXIT according to the spec. Remove the SYS_HELLO.

Signed-off-by: Chuanxiao Dong <[email protected]>
@cxdong @vijaydhanraj
syscall: Add syscall macro
73e1dcd 
Add macro to define 5 raw syscalls, which take different number of
input arguement. The syscall ABI follows the published system call
spec[1]. To trigger syscall to kernel, int 0x80 is used according to the
kernel implementation. The syscall macro is derived from [2].

[1]: https://mail.8bytes.org/pipermail/svsm-devel/2024-June/000334.html
[2]: https://gitlab.redox-os.org/redox-os/syscall/-/blob/master/src/arch/x86_64.rs

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Chuanxiao Dong <[email protected]>
@cxdong @vijaydhanraj
syscall: Define error code
8035d0f 
Define the raw error code according to syscall spec, and an enum
SysCallError to conver the raw error code to rust style error.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Chuanxiao Dong <[email protected]>
@cxdong @vijaydhanraj
syscall: Introduce exit syscall
2155fb9 
Add exit() to be used as SYS_EXIT, which takes one exit code
as an input parameter according to the spec.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Chuanxiao Dong <[email protected]>
@cxdong @vijaydhanraj
kernel/syscall: Implement close syscall
7e21ba8 
The close syscall is implemented by using the obj_remove, to remove the
ObjHandle associated witht the input object id from the current task.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Chuanxiao Dong <[email protected]>
@cxdong @vijaydhanraj
syscall/obj: Close an ObjHandle when dropped
3ae6f1d 
Implement Drop for the ObjHandle to close the underlying kernel object
when drop the ObjHandle in the user mode.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Chuanxiao Dong <[email protected]>
@peterfang @vijaydhanraj
svsm: Initialize FS earlier
ba5faf2 
FS_ROOT needs to be initialized early enough for process root directory
to take effect when setting up BSP's idle task.

Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
kernel/fs/filesystem: Add find_dir()
216f25e 
Add find_dir() which looks for a directory entry using a relative path.

Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
kernel/fs: Add FsObj
981376a 
Add FsObj which is the primary kernel object used for Class 1 syscalls.
This object represents both a file and a directory entry. Also, add
as_fs() to the Obj trait that allows for these objects to downcast back
to FsObjs.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
kernel/fs/filesystem: Add opendir()
fab5e2a 
Add opendir() which allows a Directory object to be returned.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@vijaydhanraj
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FYI this branch has conflicts with main. You might have to rebase your branch to resolve them.

Yes, done.

Freax13
Freax13 reviewed Oct 17, 2024
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vijaydhanraj and others added 9 commits October 17, 2024 09:25
@vijaydhanraj
mm/guestmem: Introduce UserPtr wrapper around GuestPtr
1b49d5a 
In addition to ensuring invalid memory access, the UserPtr
wrapper around GuestPtr validates the address passed from
the userspace to make sure it isn't pointing to kernel memory.

Signed-off-by: Vijay Dhanraj <[email protected]>
@peterfang @vijaydhanraj
kernel/syscall: Implement OPENDIR and READDIR
a95eb2e 
Implement the syscall handlers for SYS_OPENDIR and SYS_READDIR based on
the ABI spec. SYS_OPENDIR creates an FsObj representing a directory
entry.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
syscall/class1: Implement opendir() and readdir()
d0d7338 
Implement the OPENDIR and READDIR syscall interface in user space.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
kernel/task: Return TID in exec_user()
b7096d0 
If the user process is still running after scheduling, return its TID.
Else, indicate that it's already terminated through TaskError.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
kernel/syscall: Implement EXEC
9d7bc79 
Implement the syscall handler for SYS_EXEC. This commit also provides
the ability to specify a new root directory for the process. This is
done because EXEC allows the parent process to specify the root
directory of the new process. New threads automatically inherits its
parent's root directory.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
syscall: Implement exec()
b09df1c 
Implement the EXEC syscall interface in user space.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
init: Add init subfolder
1a0c545 
Add the initial version of init. Currently it only does exec() on a
dummy file. This is addressed in the future commits.

Introduced "make user" to compile the init process.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@peterfang @vijaydhanraj
init: Adopt opendir() and readdir() syscalls
3e71a96 
Use opendir() and readdir() for dm discovery. Currently, it naively runs
the first file discovered under /bin.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Peter Fang <[email protected]>
@cxdong @vijaydhanraj
dm: Add initial device model project
e051109 
The device model is a user mode program which manages VM's life cycles
and handles various vmexits events. The initial version just calls exit()
syscall without doing anything else.

As this is a user mode program, not sure what is the preferred way to
put this project, just put it as a sub folder in coconut-svsm and in the
workspace. If in the workspace is not preferred, this can be changed in
the future.

Co-developed-by: Vijay Dhanraj <[email protected]>
Signed-off-by: Chuanxiao Dong <[email protected]>
Freax13
Freax13 approved these changes Oct 17, 2024
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Looks good to me, thanks!

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