[LTP] [PATCH] mm/vma01: consider topdown and bottomup allocation

[LTP] [PATCH] mm/vma01: consider topdown and bottomup allocation

[Caspar Zhang]

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When calculating VMAs, results differ in topdown and bottomup memory
allocation mechanisms. This patch fix the potential failures and should
work like below:

In topdown allocation, the start addr in second VMA should be smaller
than first one, i.e.:

    u======t------(t+3*ps)
      2nd    1st

Thus, in buggy kernel, if we find a VMA mapping entry in child like:

    start_addr == u && end_addr == t+3*ps;

the test would go fail. Otherwise, in good kernel, we should see

    start_addr1 == u && end_addr1 == t;
    start_addr2 == t && end_addr2 == t+3*ps;

While in bottomup allocation, it's different:

    t------u======(t+6*ps)
      1st    2nd

Here in buggy kernel, we can see VMA mapping entry like this:

    start_addr == t && end_addr == t+6*ps;

And in good kernel:

    start_addr1 == t && end_addr1 == u;
    start_addr2 == u && end_addr2 == t+6*ps;

Signed-off-by: Caspar Zhang <caspar@casparzhang.com>
---
 testcases/kernel/mem/vma/vma01.c |   35 ++++++++++++++++++++++-------------
 1 files changed, 22 insertions(+), 13 deletions(-)


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diff --git a/testcases/kernel/mem/vma/vma01.c b/testcases/kernel/mem/vma/vma01.c
index 398d7a1..16ee078 100644
--- a/testcases/kernel/mem/vma/vma01.c
+++ b/testcases/kernel/mem/vma/vma01.c
@@ -59,7 +59,7 @@ char *TCID = "vma01";
 int TST_TOTAL = 1;
 
 static void check_vma(void);
-static void *get_end_addr(void *addr_s, char *mapfile);
+static void *get_end_addr(void *addr_s);
 static void check_status(int status);
 static void setup(void);
 static void cleanup(void);
@@ -90,9 +90,10 @@ int main(int argc, char **argv)
 static void check_vma(void)
 {
 	int status;
-	void *t, *u, *x, *y;
+	int topdown;
+	void *t, *u, *x;
 
-	t = mmap(NULL, 3*ps, PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, 0, 0);
+	t = mmap(NULL, 3*ps, PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
 	if (t == MAP_FAILED)
 		tst_brkm(TBROK|TERRNO, cleanup, "mmap");
 	memset(t, 1, ps);
@@ -103,21 +104,29 @@ static void check_vma(void)
 	case 0:
 		memset(t, 2, ps);
 		u = mmap(t + 3*ps, 3*ps, PROT_WRITE,
-			    MAP_ANONYMOUS|MAP_PRIVATE, 0, 0);
+			    MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
 		if (u == MAP_FAILED) {
-			perror("mmap failed.\n");
+			perror("mmap");
 			exit(255);
 		}
+		topdown = (u > t) ? 0 : 1;
 		printf("parent: t = %p\n", t);
 		printf("child : u = %p\n", u);
 		memset(u, 2, ps);
 
-		x = get_end_addr(u, MAPS_FILE);
-		if (x == u + 6*ps)
-			exit(1);
-		if (x == u + 3*ps) {
-			y = get_end_addr(x, MAPS_FILE);
-			if (y == x + 3*ps)
+		if (topdown) {
+			x = get_end_addr(u);
+			printf("child : x = %p\n", x);
+			if (x == t + 3*ps)
+				exit(1);
+			else if (x == t && get_end_addr(x) == t + 3*ps)
+				exit(0);
+		} else {
+			x = get_end_addr(t);
+			printf("child : x = %p\n", x);
+			if (x == t + 6*ps)
+				exit(1);
+			else if (x == u && get_end_addr(x) == t + 6*ps)
 				exit(0);
 		}
 		exit(255);
@@ -131,13 +140,13 @@ static void check_vma(void)
 	}
 }
 
-static void *get_end_addr(void *addr_s, char *mapfile)
+static void *get_end_addr(void *addr_s)
 {
 	FILE *fp;
 	void *s, *t;
 	char buf[BUFSIZ];
 
-	fp = fopen(mapfile, "r");
+	fp = fopen(MAPS_FILE, "r");
 	if (fp == NULL)
 		tst_brkm(TBROK|TERRNO, cleanup, "fopen");
 	while (fgets(buf, BUFSIZ, fp) != NULL) {

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Re: [LTP] [PATCH] mm/vma01: consider topdown and bottomup allocation

[Caspar Zhang]

On 06/25/2012 11:22 AM, Caspar Zhang wrote:
> 
> When calculating VMAs, results differ in topdown and bottomup memory
> allocation mechanisms. This patch fix the potential failures and should
> work like below:
> 
> In topdown allocation, the start addr in second VMA should be smaller
> than first one, i.e.:
> 
>     u======t------(t+3*ps)
>       2nd    1st
> 
> Thus, in buggy kernel, if we find a VMA mapping entry in child like:
> 
>     start_addr == u && end_addr == t+3*ps;
> 
> the test would go fail. Otherwise, in good kernel, we should see
> 
>     start_addr1 == u && end_addr1 == t;
>     start_addr2 == t && end_addr2 == t+3*ps;
> 
> While in bottomup allocation, it's different:
> 
>     t------u======(t+6*ps)
>       1st    2nd
> 
> Here in buggy kernel, we can see VMA mapping entry like this:
> 
>     start_addr == t && end_addr == t+6*ps;
> 
> And in good kernel:
> 
>     start_addr1 == t && end_addr1 == u;
>     start_addr2 == u && end_addr2 == t+6*ps;
> 
> Signed-off-by: Caspar Zhang <caspar@casparzhang.com>
> ---
>  testcases/kernel/mem/vma/vma01.c |   35 ++++++++++++++++++++++-------------
>  1 files changed, 22 insertions(+), 13 deletions(-)
> 

The patch itself passes my test, yet I give it a self-NAK for now. Needs
one more patch to resolve the issue hejianet brought up.

Caspar

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