RISC-V Disassembly of NuttX ecall to OpenSBI. See https://lupyuen.github.io/articles/sbi

nuttx-ecall-opensbi.S

// Make an ecall to OpenSBI. Based on
// https://github.com/apache/nuttx/blob/master/arch/risc-v/src/common/supervisor/riscv_sbi.c#L52-L77
// https://github.com/riscv-software-src/opensbi/blob/master/firmware/payloads/test_main.c
static struct sbiret sbi_ecall(unsigned int extid, unsigned int fid,
    4020f0cc:	88aa                	mv	a7,a0
    4020f0ce:	882e                	mv	a6,a1
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:284
  register long r1 asm("a1") = (long)(parm1);
  register long r2 asm("a2") = (long)(parm2);
  register long r3 asm("a3") = (long)(parm3);
  register long r4 asm("a4") = (long)(parm4);
  register long r5 asm("a5") = (long)(parm5);
  register long r6 asm("a6") = (long)(fid);
    4020f0d0:	1802                	slli	a6,a6,0x20
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:285
  register long r7 asm("a7") = (long)(extid);
    4020f0d2:	1882                	slli	a7,a7,0x20
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:272
static struct sbiret sbi_ecall(unsigned int extid, unsigned int fid,
    4020f0d4:	1141                	addi	sp,sp,-16
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:278
  register long r0 asm("a0") = (long)(parm0);
    4020f0d6:	8532                	mv	a0,a2
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:279
  register long r1 asm("a1") = (long)(parm1);
    4020f0d8:	85b6                	mv	a1,a3
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:280
  register long r2 asm("a2") = (long)(parm2);
    4020f0da:	4601                	li	a2,0
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:281
  register long r3 asm("a3") = (long)(parm3);
    4020f0dc:	4681                	li	a3,0
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:282
  register long r4 asm("a4") = (long)(parm4);
    4020f0de:	4701                	li	a4,0
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:283
  register long r5 asm("a5") = (long)(parm5);
    4020f0e0:	4781                	li	a5,0
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:284
  register long r6 asm("a6") = (long)(fid);
    4020f0e2:	02085813          	srli	a6,a6,0x20
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:285
  register long r7 asm("a7") = (long)(extid);
    4020f0e6:	0208d893          	srli	a7,a7,0x20
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:287

  asm volatile
    4020f0ea:	00000073          	ecall
nuttx/boards/risc-v/jh7110/star64/src/jh7110_appinit.c:298
     );

	ret.error = r0;
	ret.value = r1;
  return ret;
}
    4020f0ee:	0141                	addi	sp,sp,16
    4020f0f0:	8082                	ret