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Improve cancellations, randomness, and time

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- Exhaustively document cancellation points
- Rename SIGCANCEL to SIGTHR just like BSDs
- Further improve POSIX thread cancellations
- Ensure asynchronous cancellations work correctly
- Elevate the quality of getrandom() and getentropy()
- Make futexes cancel correctly on OpenBSD 6.x and 7.x
- Add reboot.com and shutdown.com to examples directory
- Remove underscore prefix from awesome timespec_*() APIs
- Create assertions that help verify our cancellation points
- Remove bad timespec APIs (cmp generalizes eq/ne/gt/gte/lt/lte)
This commit is contained in:
Justine Tunney 2022-11-05 19:49:41 -07:00
parent 0d7c265392
commit 3f0bcdc3ef
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GPG key ID: BE714B4575D6E328
173 changed files with 1599 additions and 782 deletions
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42
libc/sysv/systemfive.S
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@ -110,7 +110,7 @@ __pid: .quad 0
systemfive_cp:
push %rbp
mov %rsp,%rbp
mov %rsp,%rbp # so backtraces work
systemfive_cancellable: # our pthread_cancel() miracle code
cmpb $0,__tls_enabled(%rip) # inspired by the musl libc design!
je 1f # we handle linux and bsd together!
@ -120,21 +120,24 @@ systemfive_cancellable: # our pthread_cancel() miracle code
jz 1f # it's spawn() probably
testb $PT_NOCANCEL,0x00(%r10) # PosixThread::flags
jnz 1f # canceler no cancelling
#if IsModeDbg()
testb $PT_INCANCEL,0x00(%r10)
jz 5f
#endif
cmp $0,0x04(%r10) # PosixThread::cancelled
jne systemfive_cancel # tail call for masked mode
jne systemfive_cancel # we will tail call below
1: mov %rcx,%r10 # move the fourth argument
clc # no cancellable system calls exist
syscall # that have 7+ args on the bsd OSes
systemfive_cancellable_end: # i/o calls park here for long time
pop %rbp
jc systemfive_errno
jmp 0f
jc 3f # we're now out of the limbo state!
1: cmp $-4095,%rax # but we still check again on eintr
jae 2f
jnc 2f
neg %rax # turns bsd errno to system v errno
2: cmp $-4095,%rax # but we still check again on eintr
jae 3f # branch because system call failed
ret # done if the system call succeeded
2: neg %eax # now examine the nature of failure
3: cmp EINTR(%rip),%eax # did SIGCANCEL cancel our i/o call
3: neg %eax # now examine the nature of failure
cmp EINTR(%rip),%eax # did the SIGTHR cancel our IO call
jne systemfive_errno # werent interrupted by OnSigCancel
cmpb $0,__tls_enabled(%rip) # make sure it's safe to grab %fs:0
je systemfive_errno # tls is disabled we can't continue
@ -146,11 +149,22 @@ systemfive_cancellable_end: # i/o calls park here for long time
jnz systemfive_errno # cancellation is disabled
cmp $0,0x04(%rcx) # PosixThread::cancelled
je systemfive_errno # we aren't actually cancelled
jmp 1f # now we are in fact cancelled
systemfive_cancel:
jmp 4f # now we are in fact cancelled
systemfive_cancel: # SIGTHR will jump here too
pop %rbp
1: jmp _pthread_cancel_sys # must be linked if we're cancelled
.weak _pthread_cancel_sys
4: jmp _pthread_cancel_sys # tail call
.weak _pthread_cancel_sys # must be linked if we're cancelled
#if IsModeDbg()
not_a_cancellation_point: # need BEGIN/END_CANCELLATION_POINT
nop
.weak report_cancellation_point
5: ezlea report_cancellation_point,cx
test %rcx,%rcx
jz 6f
call *%rcx
6: ud2
nop
#endif
.globl systemfive_cancellable_end
.globl systemfive_cancellable
.globl systemfive_cancel
@ -169,7 +183,7 @@ systemfive_linux:
mov %rsp,%rbp # having frame will help backtraces
syscall # this is known as a context switch
pop %rbp # next we check to see if it failed
0: cmp $-4095,%rax # system five nexgen32e abi § a.2.1
cmp $-4095,%rax # system five nexgen32e abi § a.2.1
jae systemfive_error # encodes errno as neg return value
ret
.endfn systemfive_linux,globl,hidden