Lthreads disentangled from musl #403
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vtikoo
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@vtikoo Could you set the PR to draft mode if it's not ready for merging yet? |
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Please can you create a draft musl PR for the musl changes so that I can review them as well? Thanks. |
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@davidchisnall the musl PR is here - lsds/sgx-lkl-musl#18 |
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Vikas. If you can verify that auxv is 16-byte aligned, I will approve. Also I notice that some of the standard AT_* variables are missing in auxv. This is fine for now but when we back out certain musl libc changes, they will be needed to find the elf header, program headers, and the elf entry point.
| @@ -90,6 +91,8 @@ static void init_wireguard() | |||
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| static int startmain(void* args) | |||
| { | |||
| __init_libc(sgxlkl_enclave_state.elf64_stack.envp, | |||
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Don't worry. My feature.split branch will re-organize this after check in.
| @@ -150,9 +156,8 @@ int __libc_init_enclave(int argc, char** argv) | |||
| max_lthreads = next_power_of_2(max_lthreads); | |||
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| newmpmcq(&__scheduler_queue, max_lthreads, 0); | |||
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| __init_libc(envp, argv[0]); | |||
| __init_tls(); | |||
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Just double checking. Has the call to this function gone away completely? (__init_tls)?
| { | ||
| // By default auxv[AT_RANDOM] points to a buffer with 16 random bytes. | ||
| uint64_t *rbuf = (uint64_t*)buf_ptr; | ||
| buf_ptr += 16; |
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Is this buffer 16-byte aligned? I think the ABI requires it.
| auxv[23] = !sgxlkl_in_sw_debug_mode(); | ||
| auxv[24] = AT_NULL; | ||
| auxv[25] = 0; | ||
| } |
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The following seem to be missing:
- AT_BASE -- base address of image
- AT_SYSINFO_EHDR -- the ELF header address
- AT_PHDR - the program header address
- AT_PHNUM - the number of program headers
- AT_ENTRY - address of the entry point
These are usually passed by the loader. It may work without them for now, but these may be needed later when we want to just call _start().
You can check in without these I think.
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AT_PHDR is needed for unwind libraries. We probably can't throw an exception through qsort without that. That said, I've never actually seen code in the wild that wants to throw exceptions through libc functions outside of test suites: if you're using C++, there are significantly more efficient ways of sorting than calling libc's qsort and very few other libc functions take function pointer arguments.
Summary
Fixes #156
Corresponding sgx-lkl-musl PR: lsds/sgx-lkl-musl#18