musl/src/thread/mips, branch v1.2.2 musl - an implementation of the standard library for Linux-based systems make arch __clone backends hidden 2018-09-12T18:34:31+00:00 Rich Felker dalias@aerifal.cx 2018-09-10T19:36:33+00:00 f5f7673d71f843b423e60bbdd7de49fd1bbcc8c1 these are not a public interface and are not intended to be callable from anywhere but the public clone function or other places in libc. 
these are not a public interface and are not intended to be callable
from anywhere but the public clone function or other places in libc.
mips archs: fix runaway execution if start fn passed to clone returns 2018-08-18T15:22:28+00:00 Segev Finer segev208@gmail.com 2018-08-15T17:46:18+00:00 8b2b61e0001281be0dcd3dedc899bf187172fecb Call SYS_exit on return from fn in __clone. This is the expected behavior of this function. Without this the child task will crash on return from fn, since it will return to nowhere. 
Call SYS_exit on return from fn in __clone. This is the expected
behavior of this function. Without this the child task will crash on
return from fn, since it will return to nowhere.
remove workaround for broken mips assemblers 2016-02-08T21:07:09+00:00 Rich Felker dalias@aerifal.cx 2016-02-08T21:07:09+00:00 869a9df5b5f7da57ebd86d146e25f78450678eeb the workaround was for a bug that botched .gpword references to local labels, applying a nonsensical random offset of -0x4000 to them. this reverses commit 5e396fb996a80b035d0f6ecf7fed50f68aa3ebb7 and a removes a similar hack that was added to syscall_cp.s in the later commit 756c8af8589265e99e454fe3adcda1d0bc5e1963. it turns out one additional instance of the same idiom, the GETFUNCSYM macro in arch/mips/reloc.h, was still affected by the assembler bug and does not admit an easy workaround without making assumptions about how the macro is used. the previous workarounds made static linking work but left the early-stage dynamic linker broken and thus had limited usefulness. instead, affected users (using binutils versions older than 2.20) will need to fix the bug on the binutils side; the trivial patch is commit 453f5985b13e35161984bf1bf657bbab11515aa4 in the binutils-gdb repository. 
the workaround was for a bug that botched .gpword references to local
labels, applying a nonsensical random offset of -0x4000 to them.

this reverses commit 5e396fb996a80b035d0f6ecf7fed50f68aa3ebb7 and a
removes a similar hack that was added to syscall_cp.s in the later
commit 756c8af8589265e99e454fe3adcda1d0bc5e1963. it turns out one
additional instance of the same idiom, the GETFUNCSYM macro in
arch/mips/reloc.h, was still affected by the assembler bug and does
not admit an easy workaround without making assumptions about how the
macro is used. the previous workarounds made static linking work but
left the early-stage dynamic linker broken and thus had limited
usefulness.

instead, affected users (using binutils versions older than 2.20) will
need to fix the bug on the binutils side; the trivial patch is commit
453f5985b13e35161984bf1bf657bbab11515aa4 in the binutils-gdb
repository.
in mips cancellable syscall asm, don't assume gp register is valid 2016-02-04T23:01:03+00:00 Rich Felker dalias@aerifal.cx 2016-02-04T23:01:03+00:00 756c8af8589265e99e454fe3adcda1d0bc5e1963 the old __cp_cancel code path loaded the address of __cancel from the GOT using the $gp register, which happened to be set to point to the correct GOT by the calling C function, but there is no ABI requirement that this happen. instead, go the roundabout way and compute the address of __cancel via pc-relative and gp-relative addressing starting with a fake return address generated by a bal instruction, which is the same trick crt1 uses to bootstrap. 
the old __cp_cancel code path loaded the address of __cancel from the
GOT using the $gp register, which happened to be set to point to the
correct GOT by the calling C function, but there is no ABI requirement
that this happen. instead, go the roundabout way and compute the
address of __cancel via pc-relative and gp-relative addressing
starting with a fake return address generated by a bal instruction,
which is the same trick crt1 uses to bootstrap.
work around mips detached thread exit breakage due to kernel regression 2015-06-20T02:54:30+00:00 Rich Felker dalias@aerifal.cx 2015-06-20T02:54:30+00:00 ce3688eca920aa77549323f84e21f33522397115 linux kernel commit 46e12c07b3b9603c60fc1d421ff18618241cb081 caused the mips syscall mechanism to fail with EFAULT when the userspace stack pointer is invalid, breaking __unmapself used for detached thread exit. the workaround is to set $sp to a known-valid, readable address, and the simplest one to obtain is the address of the current function, which is available (per o32 calling convention) in $25. 
linux kernel commit 46e12c07b3b9603c60fc1d421ff18618241cb081 caused
the mips syscall mechanism to fail with EFAULT when the userspace
stack pointer is invalid, breaking __unmapself used for detached
thread exit. the workaround is to set $sp to a known-valid, readable
address, and the simplest one to obtain is the address of the current
function, which is available (per o32 calling convention) in $25.
mark mips cancellable syscall code as code 2015-05-25T19:56:36+00:00 Rich Felker dalias@aerifal.cx 2015-05-25T19:56:36+00:00 7b75c4877ddf22f219f944c61d939df1dee4f6d3 otherwise disassemblers treat it as data. 
otherwise disassemblers treat it as data.
consistently use hidden visibility for cancellable syscall internals 2015-04-14T15:18:59+00:00 Rich Felker dalias@aerifal.cx 2015-04-14T15:18:59+00:00 cbc02ba23cec16d7a821648ea8424546bc7f02dc in a few places, non-hidden symbols were referenced from asm in ways that assumed ld-time binding. while these is no semantic reason these symbols need to be hidden, fixing the references without making them hidden was going to be ugly, and hidden reduces some bloat anyway. in the asm files, .global/.hidden directives have been moved to the top to unclutter the actual code. 
in a few places, non-hidden symbols were referenced from asm in ways
that assumed ld-time binding. while these is no semantic reason these
symbols need to be hidden, fixing the references without making them
hidden was going to be ugly, and hidden reduces some bloat anyway.

in the asm files, .global/.hidden directives have been moved to the
top to unclutter the actual code.
prepare cancellation syscall asm for possibility of __cancel returning 2015-02-21T01:25:35+00:00 Rich Felker dalias@aerifal.cx 2015-02-21T01:25:35+00:00 f409338a9e808a09001669377c608fd2803d808d 






fix clobbering of caller's stack in mips __clone function
2013-09-16T15:52:39+00:00

Rich Felker
dalias@aerifal.cx

2013-09-16T15:52:39+00:00

cffb9e1ee2a5e8925845f0c9b79cb6c80487302c

this was resulting in crashes in posix_spawn on mips, and would have
affected applications calling clone too. since the prototype for
__clone has it as a variadic function, it may not assume that 16($sp)
is writable for use in making the syscall. instead, it needs to
allocate additional stack space, and then adjust the stack pointer
back in both of the code paths for the parent process/thread.





this was resulting in crashes in posix_spawn on mips, and would have
affected applications calling clone too. since the prototype for
__clone has it as a variadic function, it may not assume that 16($sp)
is writable for use in making the syscall. instead, it needs to
allocate additional stack space, and then adjust the stack pointer
back in both of the code paths for the parent process/thread.







fix child stack alignment on mips clone
2013-09-14T23:19:11+00:00

Rich Felker
dalias@aerifal.cx

2013-09-14T23:19:11+00:00

bfba15c9b96c2a42bd02f51ff10596a23a677926

unlike other archs, the mips version of clone was not doing anything
to align the stack pointer. this seems to have been the cause for some
SIGBUS crashes that were observed in posix_spawn.





unlike other archs, the mips version of clone was not doing anything
to align the stack pointer. this seems to have been the cause for some
SIGBUS crashes that were observed in posix_spawn.