debug : exception

[Martins3]

• https://stackoverflow.com/questions/18863199/gcc-inline-asm-jump-to-a-label-with-crossing-throwing-an-exception
  • [ ] in savereg.c, we should use m instead of r, so we will not pollute the regsiter

[Martins3]

What I expceted:

1. gup failed
2. trigger syscall

ideas:

• [ ] make hypercall as a debug entry
• [ ] kvm_vz_host_tlb_inv called everytime tlb exception ?
• [ ] TLB MOD fault and TLB LD fault, what's difference
• [ ] TLB LD fault: cause 0x10800008, PC: 00000000a19bc156, BadVaddr: 0xffffffff8900

  [53094.937397] epc = 0000000120002fe0 in dune.out[120000000+8000]
  [53094.937408] ra  = 0000000120002fdc in dune.out[120000000+8000]

[Martins3]

 1550  sudo yum install gcc
 1551  sudo yum install devtoolset-7-gcc
 1552  source /opt/rh/devtoolset-7/enable

[Martins3]

• 0x1200ba368 : GOT

• 0x12000eec0 : puts

• 0xfffbf39b40 : ???

• 0x1200208b0 : strlen

• [ ] we crash around the syscall

[Martins3]

close:

   0x0000000120023c20 <+64>:    bnez    a1,0x120023ca8 <getcwd+200>
   0x0000000120023c24 <+68>:    move    s5,a0
->   0x0000000120023c28 <+72>:    bnez    a0,0x120024110 <getcwd+1328>

[Martins3]

musl

1. https://musl.libc.org/doc/1.1.24/manual.html
2. https://stackoverflow.com/questions/42128091/linking-to-musl-with-other-headers-from-usr-include

   lrwxrwxrwx 1 root root   20 1月  19 22:54 asm -> ../../../include/asm
   lrwxrwxrwx 1 root root   28 1月  19 22:54 asm-generic -> ../../../include/asm-generic
   lrwxrwxrwx 1 root root   22 1月  19 22:52 linux -> ../../../include/linux

   Then, how to install musl in Loongson

   • ./configure
   • make
   • make install

[Martins3]

Wow : musl works

• [x] does dynamic link library work ?
• [ ] We need a syscall test suite

[Martins3]

PAGE_GRAIN

• [ ] move it out of TLB refill handler

[Martins3]

• MIPS calling convention

• .frame

• https://sourceware.org/binutils/docs/as/CFI-directives.html#CFI-directives

• https://stackoverflow.com/questions/2529185/what-are-cfi-directives-in-gnu-assembler-gas-used-for

[Martins3]

Arguments are passed as required by the “o32” ABI. Most of the time, that means that up to four arguments are passed in the registers a0– a3; but there are corner cases where something else happens, and it’s all explained in section 11.2.1.

[Martins3]

how to cross compile the musl

1. mipsenv
2. ./configure
3. make :joy:

[Martins3]

• [x] how __syscall_ret works ?

  
  long __syscall_ret(unsigned long r)
  {
  if (r > -4096UL) {
      errno = -r;
      return -1;
  }
  return r;
  }

[Martins3]

0000000120003ef0 <__errno_location>:
   120003ef0:   7c02e83b        rdhwr   v0,$29
   120003ef4:   03e00008        jr      ra
   120003ef8:   64428f5c        daddiu  v0,v0,-28836
   120003efc:   00000000        nop

[Martins3]

9.25 HWREna Register (CP0 Register 7, Select 0)

Compliance Level: Required (Release 2). The HWREna register contains a bit mask that determines which hardware registers are accessible via the RDHWR instruction when that instruction is executed in a mode in which coprocessor 0 is not enabled

[Martins3]