Tom,
Am 26.04.2019 um 13:00 schrieb Marek Vasut:
On 4/26/19 12:19 PM, Simon Goldschmidt wrote:
On Fri, Apr 26, 2019 at 11:56 AM Marek Vasut <marek.va...@gmail.com> wrote:
On 4/26/19 11:36 AM, Simon Goldschmidt wrote:
On Fri, Apr 26, 2019 at 11:32 AM Marek Vasut <marek.va...@gmail.com> wrote:
On 4/26/19 8:19 AM, Simon Goldschmidt wrote:
Marek Vasut <marek.va...@gmail.com> schrieb am Fr., 26. Apr. 2019, 00:22:
On 4/25/19 9:22 PM, Simon Goldschmidt wrote:
If the malloc range passed to mem_malloc_init() is at the end of address
range and 'start + size' overflows to 0, following allocations fail as
mem_malloc_end is zero (which looks like uninitialized).
Fix this by subtracting 1 of 'start + size' overflows to zero.
Signed-off-by: Simon Goldschmidt <simon.k.r.goldschm...@gmail.com>
Since there's no way this fits without breaking smartweb, I'd rather
drop this for now in order to get 1/2 accepted.
Regards,
Simon
---
Changes in v5:
- this patch was 1/2 in v4 but is now 2/2 as the 2nd patch of v4 has
already been accepted
- rearrange the code to make it only 8 bytes plus in code size for arm
(which fixes smartweb SPL overflowing)
common/dlmalloc.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/common/dlmalloc.c b/common/dlmalloc.c
index 6f12a18d54..38859ecbd4 100644
--- a/common/dlmalloc.c
+++ b/common/dlmalloc.c
@@ -601,8 +601,12 @@ void *sbrk(ptrdiff_t increment)
void mem_malloc_init(ulong start, ulong size)
{
mem_malloc_start = start;
- mem_malloc_end = start + size;
mem_malloc_brk = start;
+ mem_malloc_end = start + size;
+ if (size > mem_malloc_end) {
+ /* overflow: malloc area is at end of address range */
+ mem_malloc_end--;
Does this mean a memory wrap-around happened ?
I don't think decrementing malloc area size by 1 is a proper solution.
You can have it overflow by 2 and decrementing by 1 won't help.
No, not a real overflow. Instead, as I tried to described in the commit
message, mem_malloc_end gets 0 if the range is at the end of addr range,
e.g. malloc start is 0xffff0000 and malloc size is 0x10000. Subtracting 1
will be enough here. It reduces the available mall of aize, but I don't
think that should be a problem.
That's a wrap-around . What happens with your example if malloc_size is
0x10001 ? Hint: It fails ...
Yes it fails. But in contrast, that's an invalid configuration, while
my patch makes
a valid configuration work. I don't know if we want to fix all invalid
configurations.
Yes ? Should be easy, just clamp() size to (size, (BIT(32) - 1) -
mem_malloc_start) or similar for 64bit systems.
I'm not convinced we should. This range is normally generated using
something like:
SIZE=2048
START=RAM_END - SIZE
Normally ... on SoCFPGA . Other ARM32 platforms can have OCRAM mapped
somewhere in the middle of the address space. Take R-Car Gen2, which has
it at 0xe6300000 + 64k or something like that.
And, to make things worse, you cannot detect these overflows at compile
time, since the DRAM layout, which is passed to malloc init can come
from DT.
Thus, you might want to sanitize the input, properly.
I don't want to be overprotective here. I don't think there's much point
in fixing the out-of-ram-range check if it produces an overflow but not
fix it if it's in the middle of an address space.
Again, this patch simply fixes the case for something like this:
RAM_SIZE=0x10000
RAM_START=0xFFFF0000
so RAM_END=0
We can use clamp as you suggested, but what would it be good for
if it only fixes an out-of-range heap if an overflow occurs?
It's better than nothing. Further refinements welcome.
You could as well enter a range without RAM, that would fail as well.
That info is available in gd , but I wonder whether this is the right
place to check for it.
Indeed, that would seem misplaced here.
Regards,
Simon
A different approach to fix my valid end-of-ram configuration would be to set
the end to "start + size - 1" and to change all the checks using it. But that
would probably lead to more code size problems in various SPL...
Regards,
Simon
I got this when experimenting with full heap in socfpga. Due to other
patches not being accepted, this is not an issue currebtly, but can easily
become one on the future.
Regrds,
Simon
+ }
debug("using memory %#lx-%#lx for malloc()\n", mem_malloc_start,
mem_malloc_end);
--
Best regards,
Marek Vasut
--
Best regards,
Marek Vasut
--
Best regards,
Marek Vasut
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