On Mon, Oct 19, 2020 at 05:16:51AM +0900, Stafford Horne wrote:
commit d877322bc1adcab9850732275670409e8bcca4c4 upstream
Backport of v5.9 commit d877322bc1ad for v5.8.y and v5.4.y.
Change in backport:
- The original commit depends on a series of sparse warning fix patches. This patch elliminates that requirement.
A build failure was raised by kbuild with the following error.
drivers/android/binder.c: Assembler messages: drivers/android/binder.c:3861: Error: unrecognized keyword/register name `l.lwz ?ap,4(r24)' drivers/android/binder.c:3866: Error: unrecognized keyword/register name `l.addi ?ap,r0,0'The issue is with 64-bit get_user() calls on openrisc. I traced this to a problem where in the internally in the get_user macros there is a cast to long __gu_val this causes GCC to think the get_user call is 32-bit. This binder code is really long and GCC allocates register r30, which triggers the issue. The 64-bit get_user asm tries to get the 64-bit pair register, which for r30 overflows the general register names and returns the dummy register ?ap.
The fix here is to move the temporary variables into the asm macros. We use a 32-bit __gu_tmp for 32-bit and smaller macro and a 64-bit tmp in the 64-bit macro. The cast in the 64-bit macro has a trick of casting through __typeof__((x)-(x)) which avoids the below warning. This was borrowed from riscv.
arch/openrisc/include/asm/uaccess.h:240:8: warning: cast to pointer from integer of different sizeI tested this in a small unit test to check reading between 64-bit and 32-bit pointers to 64-bit and 32-bit values in all combinations. Also I ran make C=1 to confirm no new sparse warnings came up. It all looks clean to me.
Link: https://lore.kernel.org/lkml/202008200453.ohnhqkjQ%25lkp@intel.com/ Signed-off-by: Stafford Horne shorne@gmail.com Reviewed-by: Luc Van Oostenryck luc.vanoostenryck@gmail.com
arch/openrisc/include/asm/uaccess.h | 35 ++++++++++++++++++----------- 1 file changed, 22 insertions(+), 13 deletions(-)
Now queued up, thanks.
greg k-h