On Mon, 2018-10-22 at 21:16:26 UTC, Breno Leitao wrote:
Test ptrace-tm-spd-gpr fails on current kernel (4.19) due to a segmentation fault that happens on the child process prior to setting cptr[2] = 1. This causes the parent process to wait forever at 'while (!pptr[2])' and the test to be killed by the test harness framework by timeout, thus, failing.
The segmentation fault happens because of a inline assembly being generated as:
0x10000355c <tm_spd_gpr+492> lfs f0, 0(0)
This is reading memory position 0x0 and causing the segmentation fault.
This code is being generated by ASM_LOAD_FPR_SINGLE_PRECISION(flt_4), where flt_4 is passed to the inline assembly block as:
[flt_4] "r" (&d)
Since the inline assembly 'r' constraint means any GPR, gpr0 is being chosen, thus causing this issue when issuing a Load Floating-Point Single instruction.
This patch simply changes the constraint to 'b', which specify that this register will be used as base, and r0 is not allowed to be used, avoiding this issue.
Other than that, removing flt_2 register from the input operands, since it is not used by the inline assembly code at all.
Cc: stable@vger.kernel.org Signed-off-by: Breno Leitao leitao@debian.org Acked-by: Segher Boessenkool segher@kernel.crashing.org
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/48dc0ef19044bfb69193302fbe3a83
cheers