From 2dd14934c9138c562d93c501e88c6d6f061eb8ba Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 23 Mar 2006 00:00:09 +0100 Subject: [PATCH] spufs: allow SPU code to do syscalls An SPU does not have a way to implement system calls itself, but it can create intercepts to the kernel. This patch uses the method defined by the JSRE interface for C99 host library calls from an SPU to implement Linux system calls. It uses the reserved SPU stop code 0x2104 for this, using the structure layout and syscall numbers for ppc64-linux. I'm still undecided wether it is better to have a list of allowed syscalls or a list of forbidden syscalls, since we can't allow an SPU to call all syscalls that are defined for ppc64-linux. This patch implements the easier choice of them, with a blacklist that only prevents an SPU from calling anything that interacts with its own execution, e.g fork, execve, clone, vfork, exit, spu_run and spu_create and everything that deals with signals. Signed-off-by: Arnd Bergmann Signed-off-by: Paul Mackerras --- arch/powerpc/platforms/cell/spufs/run.c | 91 +++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) (limited to 'arch/powerpc/platforms/cell/spufs') diff --git a/arch/powerpc/platforms/cell/spufs/run.c b/arch/powerpc/platforms/cell/spufs/run.c index 18ea8866c61..c04e078c0fe 100644 --- a/arch/powerpc/platforms/cell/spufs/run.c +++ b/arch/powerpc/platforms/cell/spufs/run.c @@ -76,6 +76,90 @@ static inline int spu_reacquire_runnable(struct spu_context *ctx, u32 *npc, return 0; } +/* + * SPU syscall restarting is tricky because we violate the basic + * assumption that the signal handler is running on the interrupted + * thread. Here instead, the handler runs on PowerPC user space code, + * while the syscall was called from the SPU. + * This means we can only do a very rough approximation of POSIX + * signal semantics. + */ +int spu_handle_restartsys(struct spu_context *ctx, long *spu_ret, + unsigned int *npc) +{ + int ret; + + switch (*spu_ret) { + case -ERESTARTSYS: + case -ERESTARTNOINTR: + /* + * Enter the regular syscall restarting for + * sys_spu_run, then restart the SPU syscall + * callback. + */ + *npc -= 8; + ret = -ERESTARTSYS; + break; + case -ERESTARTNOHAND: + case -ERESTART_RESTARTBLOCK: + /* + * Restart block is too hard for now, just return -EINTR + * to the SPU. + * ERESTARTNOHAND comes from sys_pause, we also return + * -EINTR from there. + * Assume that we need to be restarted ourselves though. + */ + *spu_ret = -EINTR; + ret = -ERESTARTSYS; + break; + default: + printk(KERN_WARNING "%s: unexpected return code %ld\n", + __FUNCTION__, *spu_ret); + ret = 0; + } + return ret; +} + +int spu_process_callback(struct spu_context *ctx) +{ + struct spu_syscall_block s; + u32 ls_pointer, npc; + char *ls; + long spu_ret; + int ret; + + /* get syscall block from local store */ + npc = ctx->ops->npc_read(ctx); + ls = ctx->ops->get_ls(ctx); + ls_pointer = *(u32*)(ls + npc); + if (ls_pointer > (LS_SIZE - sizeof(s))) + return -EFAULT; + memcpy(&s, ls + ls_pointer, sizeof (s)); + + /* do actual syscall without pinning the spu */ + ret = 0; + spu_ret = -ENOSYS; + npc += 4; + + if (s.nr_ret < __NR_syscalls) { + spu_release(ctx); + /* do actual system call from here */ + spu_ret = spu_sys_callback(&s); + if (spu_ret <= -ERESTARTSYS) { + ret = spu_handle_restartsys(ctx, &spu_ret, &npc); + } + spu_acquire(ctx); + if (ret == -ERESTARTSYS) + return ret; + } + + /* write result, jump over indirect pointer */ + memcpy(ls + ls_pointer, &spu_ret, sizeof (spu_ret)); + ctx->ops->npc_write(ctx, npc); + ctx->ops->runcntl_write(ctx, SPU_RUNCNTL_RUNNABLE); + return ret; +} + static inline int spu_process_events(struct spu_context *ctx) { struct spu *spu = ctx->spu; @@ -107,6 +191,13 @@ long spufs_run_spu(struct file *file, struct spu_context *ctx, ret = spufs_wait(ctx->stop_wq, spu_stopped(ctx, status)); if (unlikely(ret)) break; + if ((*status & SPU_STATUS_STOPPED_BY_STOP) && + (*status >> SPU_STOP_STATUS_SHIFT == 0x2104)) { + ret = spu_process_callback(ctx); + if (ret) + break; + *status &= ~SPU_STATUS_STOPPED_BY_STOP; + } if (unlikely(ctx->state != SPU_STATE_RUNNABLE)) { ret = spu_reacquire_runnable(ctx, npc, status); if (ret) -- cgit v1.2.3