MIPS: math-emu: Correct the emulation of microMIPS ADDIUPC instruction

Emulate the microMIPS ADDIUPC instruction directly in `mips_dsemul'.  If
executed in the emulation frame, this instruction produces an incorrect
result, because the value of the PC there is not the same as where the
instruction originated.

Reshape code so as to handle all microMIPS cases together.

Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12175/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/include/uapi/asm/inst.h b/arch/mips/include/uapi/asm/inst.h
index 9b44d5a816fa3ee64faf18a80c7f415dfb681a4d..b145749c743f6e995e3226a0a4b374bc65f49f10 100644 (file)
--- a/arch/mips/include/uapi/asm/inst.h
+++ b/arch/mips/include/uapi/asm/inst.h
@@ -799,6 +799,13 @@ struct mm_x_format {               /* Scaled indexed load format (microMIPS) */
        ;)))))
 };
 
+struct mm_a_format {           /* ADDIUPC format (microMIPS) */
+       __BITFIELD_FIELD(unsigned int opcode : 6,
+       __BITFIELD_FIELD(unsigned int rs : 3,
+       __BITFIELD_FIELD(signed int simmediate : 23,
+       ;)))
+};
+
 /*
  * microMIPS instruction formats (16-bit length)
  */
@@ -940,6 +947,7 @@ union mips_instruction {
        struct mm_i_format mm_i_format;
        struct mm_m_format mm_m_format;
        struct mm_x_format mm_x_format;
+       struct mm_a_format mm_a_format;
        struct mm_b0_format mm_b0_format;
        struct mm_b1_format mm_b1_format;
        struct mm16_m_format mm16_m_format ;

diff --git a/arch/mips/math-emu/dsemul.c b/arch/mips/math-emu/dsemul.c
index 32ec5d7e17281d2efc9307471da16bdde50f0bbc..77a623db3b380f304dca07479847853037ceb20e 100644 (file)
--- a/arch/mips/math-emu/dsemul.c
+++ b/arch/mips/math-emu/dsemul.c
@@ -43,10 +43,30 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
        int err;
 
        /* NOP is easy */
-       if ((get_isa16_mode(regs->cp0_epc) && ((ir >> 16) == MM_NOP16)) ||
-           (ir == 0))
+       if (ir == 0)
                return -1;
 
+       /* microMIPS instructions */
+       if (get_isa16_mode(regs->cp0_epc)) {
+               union mips_instruction insn = { .word = ir };
+
+               /* NOP16 aka MOVE16 $0, $0 */
+               if ((ir >> 16) == MM_NOP16)
+                       return -1;
+
+               /* ADDIUPC */
+               if (insn.mm_a_format.opcode == mm_addiupc_op) {
+                       unsigned int rs;
+                       s32 v;
+
+                       rs = (((insn.mm_a_format.rs + 0x1e) & 0xf) + 2);
+                       v = regs->cp0_epc & ~3;
+                       v += insn.mm_a_format.simmediate << 2;
+                       regs->regs[rs] = (long)v;
+                       return -1;
+               }
+       }
+
        pr_debug("dsemul %lx %lx\n", regs->cp0_epc, cpc);
 
        /*