Implement initial userspace support #467

vijaydhanraj · 2024-09-25T12:18:35Z

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

Some preliminary review comments.

kernel/src/string.rs

kernel/src/syscall/class1.rs

kernel/src/fs/obj.rs

kernel/src/syscall/class0.rs

init/init.lds

Makefile

init/.gitignore

init/src/main.rs

vijaydhanraj · 2024-10-04T08:44:58Z

Some preliminary review comments.

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

Freax13

I don't have time for a full review right now, I'll do that sometime next week.

kernel/src/mm/guestmem.rs

kernel/src/syscall/class0.rs

Freax13 · 2024-10-07T11:18:14Z

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).

vijaydhanraj · 2024-10-07T22:31:49Z

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.

kernel/src/cpu/idt/svsm.rs

kernel/src/mm/guestmem.rs

init/src/main.rs

kernel/src/mm/guestmem.rs

kernel/src/syscall/class1.rs

kernel/src/task/tasks.rs

init/src/main.rs

kernel/src/cpu/idt/svsm.rs

kernel/src/mm/guestmem.rs

kernel/src/syscall/class0.rs

kernel/src/mm/guestmem.rs

kernel/src/syscall/class1.rs

syscall/src/call.rs

Freax13 · 2024-10-16T08:28:34Z

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

kernel/src/mm/guestmem.rs

kernel/src/syscall/class1.rs

syscall/src/def.rs

vijaydhanraj · 2024-10-16T20:04:11Z

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

Yes, done.

kernel/src/mm/guestmem.rs

Freax13

Looks good to me, thanks!

joergroedel · 2024-10-23T15:07:04Z

Thanks for that work, it is pretty impressive! Although it is hard to review on all levels due to its size:

 .github/workflows/rust.yml     |  2 +-
 Cargo.lock                     | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml                     |  5 +++++
 Makefile                       | 16 ++++++++++++++--
 dm/Cargo.toml                  | 15 +++++++++++++++
 dm/build.rs                    |  6 ++++++
 dm/dm.lds                      | 37 +++++++++++++++++++++++++++++++++++++
 dm/src/main.rs                 | 25 +++++++++++++++++++++++++
 elf/src/program_header.rs      |  3 +++
 init/Cargo.toml                | 16 ++++++++++++++++
 init/build.rs                  |  6 ++++++
 init/init.lds                  | 37 +++++++++++++++++++++++++++++++++++++
 init/src/main.rs               | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/src/cpu/idt/svsm.rs     | 12 ++++++++----
 kernel/src/error.rs            | 27 +++++++++++++++++++++++++++
 kernel/src/fs/api.rs           |  1 +
 kernel/src/fs/filesystem.rs    | 60 +++++++++++++++++++++++++++++++++++++++++++++++++-----------
 kernel/src/fs/mod.rs           |  2 ++
 kernel/src/fs/obj.rs           | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/src/mm/guestmem.rs      | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/src/string.rs           | 11 +++++++++++
 kernel/src/svsm.rs             | 13 +++++++------
 kernel/src/syscall/class0.rs   | 42 ++++++++++++++++++++++++++++++++++++++++++
 kernel/src/syscall/class1.rs   | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/src/syscall/handlers.rs | 21 ---------------------
 kernel/src/syscall/mod.rs      |  6 ++++--
 kernel/src/syscall/obj.rs      | 13 ++++++++++++-
 kernel/src/task/exec.rs        | 17 ++++++++++++-----
 kernel/src/task/schedule.rs    |  8 ++++++--
 kernel/src/task/tasks.rs       | 19 +++++++++++++++++--
 syscall/Cargo.toml             |  1 +
 syscall/src/call.rs            | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 syscall/src/class0.rs          | 33 +++++++++++++++++++++++++++++++++
 syscall/src/class1.rs          | 38 ++++++++++++++++++++++++++++++++++++++
 syscall/src/def.rs             | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 syscall/src/lib.rs             | 10 ++++++++--
 syscall/src/numbers.rs         | 10 ----------
 syscall/src/obj.rs             | 15 +++++++++++++++
 38 files changed, 939 insertions(+), 69 deletions(-)

Can you please split this into smaller PRs which we can merge one at a time? Please start with the system call interface and implementation. This PR can be rebased then on what has already been merged.

vijaydhanraj · 2024-10-23T17:11:19Z

Sure, I can split this into smaller PRs. Would splitting commits into the below PRs be helpful?

PR#8: Introduce a simple template for initial device model
- dm: Add initial device model project
- init: Extend opendir() and readdir() for dm discovery
PR#7: Add the initial version of init
PR#6: Introduce exec syscall
- syscall: Implement exec()
- kernel/syscall: Implement EXEC
- kernel/task: Return TID in exec_user()
PR#5: Introduce opendir and readdir syscalls
- syscall/class1: Implement opendir() and readdir()
- kernel/syscall: Implement OPENDIR and READDIR
- kernel/fs/filesystem: Add opendir()
- kernel/fs: Add FsObj
- kernel/fs/filesystem: Add find_dir()
- svsm: Initialize FS earlier
PR#4: Introduce exit and open syscalls
- syscall/obj: Close an ObjHandle when dropped
- kernel/syscall: Implement close syscall
- syscall: Introduce exit syscall
PR#3: Introduce syscall interface and error code
- syscall: Define error code
- syscall: Add syscall macro
PR#2: Introduce UserPtr wrapper around GuestPtr
PR#1: Few bookkeeping and clean-up commits
- kernel/cpu/idt: Remove SYS_HELLO for implementing formal syscalls
- kernel/syscall: Rename handlers.rs to class0.rs
- syscall: Rename numbers.rs to def.rs
- syscall: Add Obj trait

Freax13 · 2024-10-25T07:39:03Z

FYI, we merged SMAP support in #473, this PR will have to be adjusted accordingly.

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]>

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]>

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]>

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]>

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]>

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]>

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]>

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]>

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]>

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]>

Add find_dir() which looks for a directory entry using a relative path. Signed-off-by: Peter Fang <[email protected]>

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]>

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 · 2024-10-27T23:12:22Z

Hi @joergroedel as suggested, split this PR and added a PR #502 to introduce the syscall interface implementation.

vijaydhanraj · 2024-10-27T23:18:55Z

FYI, we merged SMAP support in #473, this PR will have to be adjusted accordingly.

Hi @Freax13 thanks, I have rebased this PR.

Freax13 · 2024-10-28T08:54:31Z

Hi @Freax13 thanks, I have rebased this PR.

I meant to say that we now need to execute stac & clac in the UserPtr methods.

vijaydhanraj · 2024-10-29T06:51:51Z

Got it, will add the stac and clac as part of the read/write_ref UserPtr methods and update the PR.

vijaydhanraj · 2024-10-29T14:37:18Z

@Freax13 I have updated the PR to use stac & clac in UserPtr methods. If the changes look fine, please let me know if this should be spined out as a separate PR?

Freax13 · 2024-10-29T14:41:43Z

@Freax13 I have updated the PR to use stac & clac in UserPtr methods. If the changes look fine, please let me know if this should be spined out as a separate PR?

Personally, I don't have a problem with large PRs, but @joergroedel might object.

From your comment above:

PR#2: Introduce UserPtr wrapper around GuestPtr

It probably makes sense to add the changes to this PR.

kernel/src/mm/guestmem.rs

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]>

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]>

Implement the OPENDIR and READDIR syscall interface in user space. Co-developed-by: Vijay Dhanraj <[email protected]> Signed-off-by: Peter Fang <[email protected]>

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]>

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]>

Implement the EXEC syscall interface in user space. Co-developed-by: Vijay Dhanraj <[email protected]> Signed-off-by: Peter Fang <[email protected]>

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]>

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]>

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 reviewed Sep 25, 2024

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vijaydhanraj marked this pull request as ready for review October 9, 2024 05:56

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vijaydhanraj mentioned this pull request Oct 13, 2024

Fix ELF Parser Alignment Handling, Remove Custom Linker Script, and Improve Handling of .bss Section in Binary Parsing #483

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Freax13 reviewed Oct 15, 2024

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peterfang and others added 2 commits October 27, 2024 14:53

syscall: Add Obj trait

b96b0e1

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]>

syscall: Rename numbers.rs to def.rs

b30a194

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 and others added 11 commits October 27, 2024 14:53

kernel/syscall: Rename handlers.rs to class0.rs

7d466ca

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]>

kernel/cpu/idt: Remove SYS_HELLO for implementing formal syscalls

9d30ff7

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]>

syscall: Define error code

14e4e04

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]>

syscall: Introduce exit syscall

56404dc

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]>

kernel/syscall: Implement close syscall

e6cbe83

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]>

syscall/obj: Close an ObjHandle when dropped

d252e40

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]>

svsm: Initialize FS earlier

4331478

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]>

kernel/fs/filesystem: Add find_dir()

0a963c0

Add find_dir() which looks for a directory entry using a relative path. Signed-off-by: Peter Fang <[email protected]>

kernel/fs/filesystem: Add opendir()

50225f9

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 force-pushed the initial_userspace_support branch from e051109 to 338851f Compare October 27, 2024 23:13

vijaydhanraj force-pushed the initial_userspace_support branch from 338851f to b0c0eb6 Compare October 29, 2024 14:28

Freax13 reviewed Oct 29, 2024

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vijaydhanraj and others added 9 commits October 29, 2024 08:18

mm/guestmem: Introduce UserPtr wrapper around GuestPtr

da38410

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]>

syscall/class1: Implement opendir() and readdir()

528e9d3

Implement the OPENDIR and READDIR syscall interface in user space. Co-developed-by: Vijay Dhanraj <[email protected]> Signed-off-by: Peter Fang <[email protected]>

kernel/task: Return TID in exec_user()

abc64a5

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]>

syscall: Implement exec()

461b15e

Implement the EXEC syscall interface in user space. Co-developed-by: Vijay Dhanraj <[email protected]> Signed-off-by: Peter Fang <[email protected]>

init: Adopt opendir() and readdir() syscalls

5b0fc61

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]>

vijaydhanraj force-pushed the initial_userspace_support branch from b0c0eb6 to c081cf6 Compare October 29, 2024 15:38

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Implement initial userspace support #467

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Implement initial userspace support #467

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