From 9ef3427ac14a84002497f3c8bac346486cb36f2b Mon Sep 17 00:00:00 2001
From: Fabricio Voznika <fvoznika@google.com>
Date: Thu, 7 Feb 2019 11:40:45 -0800
Subject: Implement semctl(2) SETALL and GETALL

PiperOrigin-RevId: 232914984
Change-Id: Id2643d7ad8e986ca9be76d860788a71db2674cda
---
 pkg/sentry/kernel/semaphore/semaphore.go | 65 +++++++++++++++++++++++++++++---
 1 file changed, 60 insertions(+), 5 deletions(-)

(limited to 'pkg/sentry/kernel/semaphore')

diff --git a/pkg/sentry/kernel/semaphore/semaphore.go b/pkg/sentry/kernel/semaphore/semaphore.go
index 232a276dc..c134931cd 100644
--- a/pkg/sentry/kernel/semaphore/semaphore.go
+++ b/pkg/sentry/kernel/semaphore/semaphore.go
@@ -16,6 +16,7 @@
 package semaphore
 
 import (
+	"fmt"
 	"sync"
 
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
@@ -75,7 +76,10 @@ type Set struct {
 	perms      fs.FilePermissions
 	opTime     ktime.Time
 	changeTime ktime.Time
-	sems       []sem
+
+	// sems holds all semaphores in the set. The slice itself is immutable after
+	// it's been set, however each 'sem' object in the slice requires 'mu' lock.
+	sems []sem
 
 	// dead is set to true when the set is removed and can't be reached anymore.
 	// All waiters must wake up and fail when set is dead.
@@ -136,7 +140,7 @@ func (r *Registry) FindOrCreate(ctx context.Context, key, nsems int32, mode linu
 			}
 
 			// Validate parameters.
-			if nsems > int32(set.size()) {
+			if nsems > int32(set.Size()) {
 				return nil, syserror.EINVAL
 			}
 			if create && exclusive {
@@ -244,19 +248,20 @@ func (r *Registry) findByKey(key int32) *Set {
 func (r *Registry) totalSems() int {
 	totalSems := 0
 	for _, v := range r.semaphores {
-		totalSems += v.size()
+		totalSems += v.Size()
 	}
 	return totalSems
 }
 
 func (s *Set) findSem(num int32) *sem {
-	if num < 0 || int(num) >= s.size() {
+	if num < 0 || int(num) >= s.Size() {
 		return nil
 	}
 	return &s.sems[num]
 }
 
-func (s *Set) size() int {
+// Size returns the number of semaphores in the set. Size is immutable.
+func (s *Set) Size() int {
 	return len(s.sems)
 }
 
@@ -303,6 +308,39 @@ func (s *Set) SetVal(ctx context.Context, num int32, val int16, creds *auth.Cred
 	return nil
 }
 
+// SetValAll overrides all semaphores values, waking up waiters as needed.
+//
+// 'len(vals)' must be equal to 's.Size()'.
+func (s *Set) SetValAll(ctx context.Context, vals []uint16, creds *auth.Credentials) error {
+	if len(vals) != s.Size() {
+		panic(fmt.Sprintf("vals length (%d) different that Set.Size() (%d)", len(vals), s.Size()))
+	}
+
+	for _, val := range vals {
+		if val < 0 || val > valueMax {
+			return syserror.ERANGE
+		}
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// "The calling process must have alter permission on the semaphore set."
+	if !s.checkPerms(creds, fs.PermMask{Write: true}) {
+		return syserror.EACCES
+	}
+
+	for i, val := range vals {
+		sem := &s.sems[i]
+
+		// TODO: Clear undo entries in all processes
+		sem.value = int16(val)
+		sem.wakeWaiters()
+	}
+	s.changeTime = ktime.NowFromContext(ctx)
+	return nil
+}
+
 // GetVal returns a semaphore value.
 func (s *Set) GetVal(num int32, creds *auth.Credentials) (int16, error) {
 	s.mu.Lock()
@@ -320,6 +358,23 @@ func (s *Set) GetVal(num int32, creds *auth.Credentials) (int16, error) {
 	return sem.value, nil
 }
 
+// GetValAll returns value for all semaphores.
+func (s *Set) GetValAll(creds *auth.Credentials) ([]uint16, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// "The calling process must have read permission on the semaphore set."
+	if !s.checkPerms(creds, fs.PermMask{Read: true}) {
+		return nil, syserror.EACCES
+	}
+
+	vals := make([]uint16, s.Size())
+	for i, sem := range s.sems {
+		vals[i] = uint16(sem.value)
+	}
+	return vals, nil
+}
+
 // ExecuteOps attempts to execute a list of operations to the set. It only
 // succeeds when all operations can be applied. No changes are made if it fails.
 //
-- 
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