On 07/11/13 18:00, David Daney wrote:
Nice work...
On 11/07/2013 04:48 AM, Paul Burton wrote:
[...]
- * Algorithmics used a system call instruction, and
- * borrowed that vector. MIPS/Linux version is a bit
- * more heavyweight in the interests of portability and
- * multiprocessor support. For Linux we generate a
- * an unaligned access and force an address error exception.
+ * 1) Be a bug in the userland code, because it has a
branch/jump in
+ * a branch delay slot. So if we run out of emuframes and the
+ * userland code hangs it's not exactly the kernels fault.
s/kernels/kernel's/
Yup, thanks.
*
- * For embedded systems (stand-alone) we prefer to use a
- * non-existing CP1 instruction. This prevents us from emulating
- * branches, but gives us a cleaner interface to the exception
- * handler (single entry point).
+ * 2) Only affect that userland process, since emuframes are
allocated
+ * per-mm and kernel threads don't use them at all.
*/
+ if (!get_isa16_mode(regs->cp0_epc)) {
+ if (!ir) {
+ /* typical NOP encoding: sll r0, r0, r0 */
+is_nop:
+ regs->cp0_epc = cpc;
+ regs->cp0_cause &= ~CAUSEF_BD;
+ return 0;
+ }
- /* Ensure that the two instructions are in the same cache line */
- fr = (struct emuframe __user *)
- ((regs->regs[29] - sizeof(struct emuframe)) & ~0x7);
+ switch (inst.j_format.opcode) {
+ case bcond_op:
+ switch (inst.i_format.rt) {
+ case bltz_op:
+ case bgez_op:
+ case bltzl_op:
+ case bgezl_op:
+ case bltzal_op:
+ case bgezal_op:
+ case bltzall_op:
+ case bgezall_op:
+ goto is_branch;
+ }
+ break;
Is there any way to use the support in arch/mips/kernel/branch.c instead
of duplicating the code here?
It may require some refactoring to make it work, but I think it would be
worth it.
Ah (how had I not spotted that code?) :)
It may fit better with the (mm_)isBranchInstr functions in
arch/mips/math-emu/cp1emu.c since they already return a value specifying
whether or not the instruction is a branch. The microMIPS variant is
already used elsewhere too. I'll take a look at it.
Thanks,
Paul
- /* Verify that the stack pointer is not competely insane */
- if (unlikely(!access_ok(VERIFY_WRITE, fr, sizeof(struct emuframe))))
+ case cop1_op:
+ switch (inst.i_format.rs) {
+ case bc_op:
+ goto is_branch;
+ }
+ break;
+
+ case j_op:
+ case jal_op:
+ case beq_op:
+ case bne_op:
+ case blez_op:
+ case bgtz_op:
+ case beql_op:
+ case bnel_op:
+ case blezl_op:
+ case bgtzl_op:
+ case jalx_op:
+is_branch:
+ pr_warn("PID %d has a branch in an FP branch delay slot
at 0x%08lx\n",
+ current->pid, regs->cp0_epc);
+ goto is_nop;
+ }
+ } else {
+ if ((ir >> 16) == MM_NOP16)
+ goto is_nop;
+
+ switch (inst.mm_i_format.opcode) {
+ case mm_beqz16_op:
+ case mm_beq32_op:
+ case mm_bnez16_op:
+ case mm_bne32_op:
+ case mm_b16_op:
+ case mm_j32_op:
+ case mm_jalx32_op:
+ case mm_jal32_op:
+ goto is_branch;
+
+ case mm_pool32i_op:
+ switch (inst.mm_i_format.rt) {
+ case mm_bltz_op:
+ case mm_bltzal_op:
+ case mm_bgez_op:
+ case mm_bgezal_op:
+ case mm_blez_op:
+ case mm_bnezc_op:
+ case mm_bgtz_op:
+ case mm_beqzc_op:
+ case mm_bltzals_op:
+ case mm_bgezals_op:
+ case mm_bc2f_op:
+ case mm_bc2t_op:
+ case mm_bc1f_op:
+ case mm_bc1t_op:
+ goto is_branch;
+ }
+ break;
+
+ case mm_pool16c_op:
+ switch (inst.mm16_r5_format.rt) {
+ case mm_jr16_op:
+ case mm_jrc_op:
+ case mm_jalr16_op:
+ case mm_jalrs16_op:
+ case mm_jraddiusp_op:
+ goto is_branch;
+ }
+ break;
+ }
+ }
+
