Hi all,
the failing y2038 testcase we see in CI [1] is caused by another problem
of our syscall wrappers, this time on arm64:
/* Timeout is never read by the kernel, so NULL should be OK */
ret = XENOMAI_SYSCALL5(sc_nr, mq, msg, strlen(msg), 0, NULL);
235c: b940dfe0 ldr w0, [sp, #220]
2360: 32040000 orr w0, w0, #0x10000000
2364: 2a0003e8 mov w8, w0
--> w8 holds the syscall number
2368: b980d3e0 ldrsw x0, [sp, #208]
236c: 910043e0 add x0, sp, #0x10
2370: aa0003e1 mov x1, x0
2374: 910043e0 add x0, sp, #0x10
2378: 94000000 bl 0 <strlen>
2378: R_AARCH64_CALL26 strlen
--> w8 is clobbered
237c: aa0003e2 mov x2, x0
2380: d2800003 mov x3, #0x0 // #0
2384: d2800004 mov x4, #0x0 // #0
2388: d4000001 svc #0x0
The problem is that w8/r8 is the "Indirect result location register",
thus can be overwritten when calling a function - and that's what strlen
does.
What are we missing in our syscall black magic to prevent this? Or this
this the final call to move the wrapper into am out-of-line function?
Jan
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
