srvfs.c File Reference

#include <Fs/srvfs.h>
#include <Fs/vfs.h>
#include <Ipc/auipc.h>
#include <Fs/Dev/devhw.h>
#include <Cred/group.h>
#include <Mm/kmalloc.h>
#include <Drivers/uart.h>
#include <Hal/AA64/aa64lowlevel.h>
#include <Hal/AA64/sched.h>
#include <Serv/sysserv.h>
#include <process.h>
#include <auipc.h>
#include <fssrv.h>
#include <string.h>
#include <_null.h>

Include dependency graph for srvfs.c:

Classes
struct	Op
struct	Hist

Macros
#define	SRV_TIMEOUT_MS   3000
#define	MAX_HIST   8
#define	MAX_OPS   16
#define	HIST_STALE_US   (15ULL * 1000 * 1000)

Enumerations
enum	{ OP_FREE = 0 , OP_WAIT , OP_DONE }

Functions
uint64_t	AuGetCurrentUS ()
void	AuSrvfsNoteOpenMode (int mode)
	AuSrvfsNoteOpenMode – OpenFile tells the proxy the mode of the open it is about to do.
void	AuSrvfsSyscallEnterSlow (AA64Thread *thr)
void	AuSrvfsSyscallExitSlow (AA64Thread *thr)
int	AuSrvfsRemove (const char *path)
	AuSrvfsRemove – remove a /srv file for the RemoveFile syscall; 0 on success.
bool	AuSrvfsOwns (AuVFSNode *fsys)
	AuSrvfsOwns – true if fsys is the /srv proxy.
void	AuSrvfsInitialize (void)
	AuSrvfsInitialize – mount the /srv proxy file system.

Variables
int	g_srvfs_active
	syscall bracket hooks: restartable operations replay per-syscall history

Macro Definition Documentation

HIST_STALE_US

#define HIST_STALE_US   (15ULL * 1000 * 1000)

MAX_HIST

#define MAX_HIST   8

MAX_OPS

#define MAX_OPS   16

SRV_TIMEOUT_MS

#define SRV_TIMEOUT_MS   3000

srvfs.c – /srv, a file system served by a user-space process.

The kernel keeps no file data and no directory: every open/read/write on a /srv path becomes a request to the IPC endpoint "fs" (BaseHdr/fssrv.h), stamped with the caller's uid. The server (Process/fssrv) owns the namespace.

The hard part is waiting. A syscall that sleeps does not return up the C stack: the thread resumes after the svc instruction. So a proxy operation that has to wait for the server does this instead:

1. first execution: queue the request, remember it, rewind ELR_EL1 by one instruction and sleep – the thread resumes by re-executing the svc;
2. re-execution: the syscall runs again from its entry. Each proxy operation is matched, in order, against this thread's history for the syscall; a finished one returns its saved answer without asking the server again, a pending one polls (and sleeps again if still unanswered).

Positions are restored on replay so side effects of an earlier pass are not applied twice. The history is dropped when the syscall finally returns (the dispatcher calls AuSrvfsSyscallExit). A request the server does not answer in SRV_TIMEOUT_MS fails with an error, so a dead or stuck server never hangs a client. Reads and writes move at most one page per operation.

Enumeration Type Documentation

anonymous enum

anonymous enum

Enumerator
OP_FREE
OP_WAIT
OP_DONE

Function Documentation

AuGetCurrentUS()

uint64_t AuGetCurrentUS ( )

extern

AuSrvfsInitialize()

void AuSrvfsInitialize

(

void

)

AuSrvfsInitialize – mount the /srv proxy file system.

AuSrvfsNoteOpenMode()

void AuSrvfsNoteOpenMode

(

int

mode

)

AuSrvfsNoteOpenMode – OpenFile tells the proxy the mode of the open it is about to do.

AuSrvfsOwns()

bool AuSrvfsOwns

(

AuVFSNode *

fsys

)

AuSrvfsOwns – true if fsys is the /srv proxy.

AuSrvfsRemove()

int AuSrvfsRemove

(

const char *

path

)

AuSrvfsRemove – remove a /srv file for the RemoveFile syscall; 0 on success.

AuSrvfsSyscallEnterSlow()

void AuSrvfsSyscallEnterSlow

(

AA64Thread *

thr

)

AuSrvfsSyscallExitSlow()

void AuSrvfsSyscallExitSlow

(

AA64Thread *

thr

)

Variable Documentation

g_srvfs_active

int g_srvfs_active

syscall bracket hooks: restartable operations replay per-syscall history