Thread (32 messages) flat view 32 messages, 4 authors, 2018-06-29

Re: [PATCH v2 4/6] powerpc/pkeys: Preallocate execute-only key

From: Thiago Jung Bauermann <hidden>
Date: 2018-06-29 03:03:03

Hello,

My understanding is that this patch isn't upstream yet and it's not too
late for bikeshedding. Please ignore if this is not the case.

Ram Pai [off-list ref] writes:
quoted hunk ↗ jump to hunk
@@ -326,48 +330,7 @@ static inline bool pkey_allows_readwrite(int pkey)

 int __execute_only_pkey(struct mm_struct *mm)
 {
-	bool need_to_set_mm_pkey = false;
-	int execute_only_pkey = mm->context.execute_only_pkey;
-	int ret;
-
-	/* Do we need to assign a pkey for mm's execute-only maps? */
-	if (execute_only_pkey == -1) {
-		/* Go allocate one to use, which might fail */
-		execute_only_pkey = mm_pkey_alloc(mm);
-		if (execute_only_pkey < 0)
-			return -1;
-		need_to_set_mm_pkey = true;
-	}
-
-	/*
-	 * We do not want to go through the relatively costly dance to set AMR
-	 * if we do not need to. Check it first and assume that if the
-	 * execute-only pkey is readwrite-disabled than we do not have to set it
-	 * ourselves.
-	 */
-	if (!need_to_set_mm_pkey && !pkey_allows_readwrite(execute_only_pkey))
-		return execute_only_pkey;
-
-	/*
-	 * Set up AMR so that it denies access for everything other than
-	 * execution.
-	 */
-	ret = __arch_set_user_pkey_access(current, execute_only_pkey,
-					  PKEY_DISABLE_ACCESS |
-					  PKEY_DISABLE_WRITE);
-	/*
-	 * If the AMR-set operation failed somehow, just return 0 and
-	 * effectively disable execute-only support.
-	 */
-	if (ret) {
-		mm_pkey_free(mm, execute_only_pkey);
-		return -1;
-	}
-
-	/* We got one, store it and use it from here on out */
-	if (need_to_set_mm_pkey)
-		mm->context.execute_only_pkey = execute_only_pkey;
-	return execute_only_pkey;
+	return mm->context.execute_only_pkey;
 }
There's no reason to have a separate  __execute_only_pkey() function
anymore. Its single line can go directly in execute_only_pkey(), defined
in <asm/pkeys.h>.
-- 
Thiago Jung Bauermann
IBM Linux Technology Center
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