66 lines
2.1 KiB
C
66 lines
2.1 KiB
C
// User-level IPC library routines
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#include <inc/lib.h>
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// Receive a value via IPC and return it.
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// If 'pg' is nonnull, then any page sent by the sender will be mapped at
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// that address.
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// If 'from_env_store' is nonnull, then store the IPC sender's envid in
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// *from_env_store.
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// If 'perm_store' is nonnull, then store the IPC sender's page permission
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// in *perm_store (this is nonzero iff a page was successfully
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// transferred to 'pg').
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// If the system call fails, then store 0 in *fromenv and *perm (if
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// they're nonnull) and return the error.
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// Otherwise, return the value sent by the sender
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//
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// Hint:
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// Use 'thisenv' to discover the value and who sent it.
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// If 'pg' is null, pass sys_ipc_recv a value that it will understand
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// as meaning "no page". (Zero is not the right value, since that's
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// a perfectly valid place to map a page.)
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int32_t
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ipc_recv(envid_t *from_env_store, void *pg, int *perm_store)
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{
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int return_code;
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if((return_code = sys_ipc_recv(pg ? pg : (void*) ~0)) < 0)
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return return_code;
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if(from_env_store) *from_env_store = thisenv->env_ipc_from;
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if(perm_store) *perm_store = thisenv->env_ipc_perm;
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return thisenv->env_ipc_value;
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}
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// Send 'val' (and 'pg' with 'perm', if 'pg' is nonnull) to 'toenv'.
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// This function keeps trying until it succeeds.
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// It should panic() on any error other than -E_IPC_NOT_RECV.
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//
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// Hint:
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// Use sys_yield() to be CPU-friendly.
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// If 'pg' is null, pass sys_ipc_try_send a value that it will understand
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// as meaning "no page". (Zero is not the right value.)
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void
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ipc_send(envid_t to_env, uint32_t val, void *pg, int perm)
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{
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int return_code = -E_IPC_NOT_RECV;
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while(return_code == -E_IPC_NOT_RECV) {
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return_code = sys_ipc_try_send(to_env, val, pg ? pg : (void*) ~0, perm);
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sys_yield();
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}
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if(return_code != 0) panic("failed to send\n");
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}
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// Find the first environment of the given type. We'll use this to
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// find special environments.
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// Returns 0 if no such environment exists.
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envid_t
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ipc_find_env(enum EnvType type)
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{
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int i;
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for (i = 0; i < NENV; i++)
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if (envs[i].env_type == type)
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return envs[i].env_id;
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return 0;
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}
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