On Fri, Dec 22, 2023 at 12:50:44PM +0800, Guo Ren wrote:
On Fri, Dec 22, 2023 at 12:43 PM Leonardo Bras leobras@redhat.com wrote:
On Fri, Dec 22, 2023 at 12:26:19PM +0800, Guo Ren wrote:
On Fri, Dec 22, 2023 at 11:35 AM Leonardo Bras leobras@redhat.com wrote:
On Thu, Dec 21, 2023 at 10:46:59AM -0500, guoren@kernel.org wrote:
From: Guo Ren guoren@linux.alibaba.com
When the task is in COMPAT mode, the arch_get_mmap_end should be 2GB, not TASK_SIZE_64. The TASK_SIZE has contained is_compat_mode() detection, so change the definition of STACK_TOP_MAX to TASK_SIZE directly.
ok
Cc: stable@vger.kernel.org Fixes: add2cc6b6515 ("RISC-V: mm: Restrict address space for sv39,sv48,sv57") Signed-off-by: Guo Ren guoren@linux.alibaba.com Signed-off-by: Guo Ren guoren@kernel.org
arch/riscv/include/asm/processor.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h index f19f861cda54..1f538fc4448d 100644 --- a/arch/riscv/include/asm/processor.h +++ b/arch/riscv/include/asm/processor.h @@ -16,15 +16,13 @@
#ifdef CONFIG_64BIT #define DEFAULT_MAP_WINDOW (UL(1) << (MMAP_VA_BITS - 1)) -#define STACK_TOP_MAX TASK_SIZE_64 +#define STACK_TOP_MAX TASK_SIZE
It means STACK_TOP_MAX will be in 64BIT:
- TASK_SIZE_32 if compat_mode=y
- TASK_SIZE_64 if compat_mode=n
Makes sense for me.
#define arch_get_mmap_end(addr, len, flags) \ ({ \ unsigned long mmap_end; \ typeof(addr) _addr = (addr); \
if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \mmap_end = STACK_TOP_MAX; \else if ((_addr) >= VA_USER_SV57) \
if ((_addr) == 0 || (_addr) >= VA_USER_SV57) \ mmap_end = STACK_TOP_MAX; \ else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \ mmap_end = VA_USER_SV48; \I don't think I got this change, or how it's connected to the commit msg.
The above is just code simplification; if STACK_TOP_MAX is TASK_SIZE, then
if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \ mmap_end = STACK_TOP_MAX; \ else if ((_addr) >= VA_USER_SV57) \is equal to:
if ((_addr) == 0 || (_addr) >= VA_USER_SV57) \I am failing to understand exactly how are they equal. I mean, what in your STACK_TOP_MAX change made them equal?
#define STACK_TOP_MAX TASK_SIZE #define TASK_SIZE (is_compat_task() ? TASK_SIZE_32 : TASK_SIZE_64)
yes, I am aware. Let's do a simple test with the new code and addr = 2^27 (random 32-bit addr) and compat mode.
if ((_addr) == 0 || (_addr) >= VA_USER_SV57) // Evaluates to false: 2^27 != 0, and is < 2^57 else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) // Evaluates to false: 2^27 < 2^48 else mmap_end = VA_USER_SV39;
mmap_end = VA_USER_SV39, even in compat_mode.
We need the extra is_compat_task() if we want to return 2^32.
Thanks! Leo
See below, the behavior changed:
Before:
- addr == 0, or addr > 2^57, or compat: mmap_end = STACK_TOP_MAX
- 2^48 < addr < 2^57: mmap_end = 2^48
- 0 < addr < 2^48 : mmap_end = 2^39
Now:
- addr == 0, or addr > 2^57: mmap_end = STACK_TOP_MAX
- 2^48 < addr < 2^57: mmap_end = 2^48
- 0 < addr < 2^48 : mmap_end = 2^39
IIUC compat mode addr will be < 2^32, so will always have mmap_end = 2^39 if addr != 0. Is that desireable? (if not, above change is unneeded)
^
With your change on STACK_TOP_MAX only (not changing arch_get_mmap_end), you would have:
- compat_mode & (0 < addr < 2^32) -> mmap_end = 2^32
compat_mode -> mmap_end = 2^32
This is correct! Yeah, since you changed STACK_TOP_MAX to be 2^32 in compat mode, any addr value < 2^32 with compat value will return 2^32. (without the change in arch_get_mmap_end(), that is.)
- non-compat, addr == 0, or addr > 2^57 -> mmap_end = TASK_SIZE_64
- non-compat, (2^48 < addr < 2^57) -> mmap_end = 2^48
- non-compat, (0 < addr < 2^48) -> mmap_end = 2^39
Which seems more likely, based on Charlie comments.
Thanks, Leo
Also, unrelated to the change:
- 2^48 < addr < 2^57: mmap_end = 2^48
Is the above correct? It looks like it should be 2^57 instead, and a new if clause for 2^32 < addr < 2^48 should have mmap_end = 2^48.
Do I get it wrong?
Maybe I should move this into the optimization part.
(I will send an RFC 'fixing' the code the way I am whinking it should look like)
Thanks, Leo
-- 2.40.1
-- Best Regards Guo Ren
-- Best Regards Guo Ren