e04ca28812
Removes the "-unix" element and with it any trademark exposure to The
Open Group.
The split follows the ecosystem layout: SchOS is the system, and the
kernel has its own name. Kernel-identity strings are the only places
that take SchIFT -- uname(2) sysname, /proc/version, and the two licence
sentences that say "kernel" outright. That is what every Unix does here:
`uname -s` on Linux reports the kernel, not the distribution. Everything
a user reads as the product -- panic screen, boot menu, error prefixes,
docs, LICENSE, NOTICE -- is SchOS.
schunix.img is schos.img, the logo assets and the musl TLS patch are
renamed, and __SCHUNIX__ is __SCHOS__ (the define and the patch that
consumes it moved together).
Two things the rename broke, both found by the bootcheck suite:
- shmtest wrote "SCHUNIX-MMAP-OK" with a hardcoded length of 15 and
compared it back by hand-counted offsets (m[3]=='U', m[14]=='K').
The shorter marker left the write running two bytes past the literal
and the compare reading past the data, failing a file-backed mmap
that was working correctly. Now written and compared through one
constant with sizeof.
- bootcheck asserted a 31-byte file after appending to
"hello-from-schunix"; the shorter string makes it 29.
Both are the same mistake: a string literal whose length is written out
somewhere else. Full suite green -- base, Tty, Ps, Sock, Fb, Usb, Evdev.
44 lines
1.8 KiB
ArmAsm
44 lines
1.8 KiB
ArmAsm
/* SPDX-License-Identifier: Apache-2.0
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* SchOS — process entry point.
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*
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* This has to be assembly, and the reason is worth recording.
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*
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* exec() hands a new process its arguments in registers, not on the stack:
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* kernel/fs/exec.c sets proc->tf->rdi = argc and proc->tf->rsi = argv. Those
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* are already the first two SysV argument registers, so _start's entire job
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* is to call main and then exit — it must not touch %rdi or %rsi at all.
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*
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* It used to be written in C, capturing the incoming registers with GCC's
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*
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* register int argc_reg asm("rdi");
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*
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* That is not what local register variables mean. Both GCC and clang only
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* guarantee the binding when the variable is used as an operand of an inline
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* asm statement; reading one to pick up an incoming argument is undefined.
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* GCC happened to do the useful thing. clang compiled it to
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*
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* movl -0x4(%rbp), %eax # two uninitialised stack slots
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* movq -0x10(%rbp), %rax
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*
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* and every program was handed a garbage argc and argv. Nothing crashed --
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* init, shmtest and socktest take no arguments and passed their whole test
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* suites -- so the only symptom was `inputtest -n 6` quietly ignoring its
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* limit. A compiler-dependent way to read registers has no business being in
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* C when four instructions of assembly are exactly right.
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*/
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.text
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.globl _start
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_start:
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xorq %rbp, %rbp /* end the frame-pointer chain here */
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/* SysV wants %rsp 16-byte aligned immediately before a call, so that the
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* callee sees %rsp+8 aligned once the return address is pushed. Rounding
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* down is safe: argc and argv arrive in registers, so nothing below is
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* needed. */
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andq $-16, %rsp
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callq main /* main(%rdi = argc, %rsi = argv) */
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callq exit /* exit() is noreturn, but be certain */
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1: hlt
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jmp 1b
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