log on adding C apps on rcore

plan

• long term: porting glibc, rustc, add all kinds of apps(GUI, net, games,...) in rcore.
• middle term: porting musl, rust std on x86-64/aarch64/rv32/64
• short term: porting litc and some C apps on x86-64

2019.03.17

• jyk: busybox ls passed on aarch64.

2019.03.09

• wrj: Implement multithread: sys_clone, sys_futex.

2019.03.08

• cjj: nginx is working.
• wrj: fix fs.

2019.03.07

• cjj: Use musl to build biscuit programs(except a few using biscuit-only syscalls). Add many missing things, and a large number of biscuit programs can run now, the rest usually mostly having problems in fs and memory.

2019.03.04

jyk:

• Try to run rust std with musl on aarch64, panic at sys_mmap. Because the high 16 bits of user virtual address need to be 1, but sys_mmap doesn't consider.
• I think it's better to put kernel in the top VA range and put user programs in the bottom VA range. Need to rewrite bootloader.

2019.03.02

• cjj: Implement sys_getcwd, sys_munmap and sys_time.
• wrj: Implement a lot file system syscalls

2019.02.27

wrj: How does Biscuit implement TLS

• All TLS data is declared with __thread and put into tdata or tbss section in ELF.
• User accesses TLS data through 'thread pointer' (x86_64: fs, aarch64: TPIDR_EL0, riscv: tp)
• When a process starts, kernel put 2 copies of TLS section into its stack.
  • One for the first thread. Thread pointer (fsbase) is set to there.
  • One for the fresh copy for other threads. Kernel tells user its position by passing kinfo_t to entry.
• When creating a new thread, user first copies the fresh TLS, then pass the new address in tfork_t to kernel in sys_fork. Kernel will set thread pointer (fsbase) to it for the new thread.

wrj: How does musl implement TLS

• ELF header is contained in the first page of rodata section. It will be loaded into process memory.
• Musl looks up the auxiliary vectors in the initial stack, to find the location of ELF header. The aux vectors should contain these entries: AT_PHDR, AT_PHNUM, AT_PHENT.
• Then it parses the header to find TLS section.
• For each thread, it allocates space and copies the fresh TLS data, then set fsbase through sys_arch_prctl.

See static_init_tls() in __init_tls.c for details.

wrj:

• support TLS for musl. test coreutils: true, echo

jyk

• fixed a bug: when the context switch occurs in InactivePageTable::edit() or InactivePageTable::with() which modify TTBR1_EL1 temporarily, TTBR1_EL1 can be restored to the unmodified value after context switch.

2019.02.25

• jyk: support simple Biscuit programs on AArch64: echo, hello, cat

2019.02.24

• wrj:
  • support set fs base (for TLS)
  • then met unknown bug on musl (access address 0). it's hard to debug without backtrace...
  • Biscuit litc has only one TLS variable: errno. Just remove __thread from litc.[c|h], then a lot of programs are runnable.

2019.02.22

• wrj: update fs. refactor. implementing mmap.
• jyk: read/repeat wrj's work

2019.02.21

• wrj:
  • support simple Biscuit programs: echo, hello, cat
  • success to build std with customized musl using xargo

2019.02.20

• wrj: modify rcore syscall id to Linux64. prepare rcore-user repo.

2019.02.19

• cy: analyze litc in biscuit. found litc is a customized libc for C/C++ apps(such as redis, nginx) on biscuit x86-64
• wrj: found musl is statically linked to Rust std, hard to customize. begin port litc on rcore x86-64

2019.02.18

• cy: try to run&analyze biscuit. install goland IDE, clion IDE
• wrj: try to analyze musl libc

2019.02.17

• cy: read biscuit osdi'18 paper
• wrj: write a analysis doc for syscalls in biscuit

reference

• litc
• musl