[klibc] Add RISC-V (RV64) port

RISC-V is pretty boring.  I've cribbed most of this from the MIPS and
AArch64 ports.

I ran into difficulty with initialisation of the gp,register, which I
think has to be process-global - the psABI says that signal handlers
can rely on it, and they could come from any module.  This means that
klibc.so and the executable using it need to agree on a single value.
Currently they don't, and this causes gp-relative addressing to go
wrong.

gp-relative addressing is introduced by "relaxation" in the linker,
so I've disabled that for now.

Link: https://www.zytor.com/pipermail/klibc/2018-July/003997.html
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

12 files changed, 252 insertions, 1 deletions

diff --git a/usr/include/arch/riscv64/klibc/archconfig.h b/usr/include/arch/riscv64/klibc/archconfig.h
new file mode 100644
index 00000000000000..e85a69c003d421
--- /dev/null
+++ b/usr/include/arch/riscv64/klibc/archconfig.h
@@ -0,0 +1,15 @@
+/*
+ * include/arch/riscv64/klibc/archconfig.h
+ *
+ * See include/klibc/sysconfig.h for the options that can be set in
+ * this file.
+ *
+ */
+
+#ifndef _KLIBC_ARCHCONFIG_H
+#define _KLIBC_ARCHCONFIG_H
+
+/* We have an MMU but no fork() syscall */
+#define _KLIBC_NO_MMU 0
+
+#endif				/* _KLIBC_ARCHCONFIG_H */
diff --git a/usr/include/arch/riscv64/klibc/archsetjmp.h b/usr/include/arch/riscv64/klibc/archsetjmp.h
new file mode 100644
index 00000000000000..97d6b6bead8e00
--- /dev/null
+++ b/usr/include/arch/riscv64/klibc/archsetjmp.h
@@ -0,0 +1,27 @@
+/*
+ * arch/riscv64/include/klibc/archsetjmp.h
+ */
+
+#ifndef _KLIBC_ARCHSETJMP_H
+#define _KLIBC_ARCHSETJMP_H
+
+struct __jmp_buf {
+	unsigned long __pc;
+	unsigned long __s0;
+	unsigned long __s1;
+	unsigned long __s2;
+	unsigned long __s3;
+	unsigned long __s4;
+	unsigned long __s5;
+	unsigned long __s6;
+	unsigned long __s7;
+	unsigned long __s8;
+	unsigned long __s9;
+	unsigned long __s10;
+	unsigned long __s11;
+	unsigned long __sp;
+};
+
+typedef struct __jmp_buf jmp_buf[1];
+
+#endif				/* _SETJMP_H */
diff --git a/usr/include/arch/riscv64/klibc/archsignal.h b/usr/include/arch/riscv64/klibc/archsignal.h
new file mode 100644
index 00000000000000..560a951247a466
--- /dev/null
+++ b/usr/include/arch/riscv64/klibc/archsignal.h
@@ -0,0 +1,14 @@
+/*
+ * arch/riscv/include/klibc/archsignal.h
+ *
+ * Architecture-specific signal definitions
+ *
+ */
+
+#ifndef _KLIBC_ARCHSIGNAL_H
+#define _KLIBC_ARCHSIGNAL_H
+
+#include <asm/signal.h>
+/* No special stuff for this architecture */
+
+#endif
diff --git a/usr/include/arch/riscv64/klibc/archstat.h b/usr/include/arch/riscv64/klibc/archstat.h
new file mode 100644
index 00000000000000..f5bfa80a5d4cef
--- /dev/null
+++ b/usr/include/arch/riscv64/klibc/archstat.h
@@ -0,0 +1,28 @@
+#ifndef _KLIBC_ARCHSTAT_H
+#define _KLIBC_ARCHSTAT_H
+
+#include <klibc/stathelp.h>
+
+#define _STATBUF_ST_NSEC
+
+struct stat {
+	__stdev64	(st_dev);	/* Device */
+	unsigned long	st_ino;		/* File serial number */
+	unsigned int	st_mode;	/* File mode */
+	unsigned int	st_nlink;	/* Link count */
+	unsigned int	st_uid;		/* User ID of the file's owner */
+	unsigned int	st_gid;		/* Group ID of the file's group */
+	__stdev64	(st_rdev);	/* Device number, if device */
+	unsigned long	__pad1;
+	long		st_size;	/* Size of file, in bytes */
+	int		st_blksize;	/* Optimal block size for I/O */
+	int		__pad2;
+	long		st_blocks;	/* Number 512-byte blocks allocated */
+	struct timespec st_atim;	/* Time of last access */
+	struct timespec st_mtim;	/* Time of last modification */
+	struct timespec st_ctim;	/* Time of last status change */
+	unsigned int	__unused4;
+	unsigned int	__unused5;
+};
+
+#endif
diff --git a/usr/include/arch/riscv64/machine/asm.h b/usr/include/arch/riscv64/machine/asm.h
new file mode 100644
index 00000000000000..9effc935652ff6
--- /dev/null
+++ b/usr/include/arch/riscv64/machine/asm.h
@@ -0,0 +1,26 @@
+/*
+ * arch/riscv64/include/machine/asm.h
+ *
+ * Mostly cribbed from mips.
+ */
+
+#ifndef _MACHINE_ASM_H
+#define _MACHINE_ASM_H
+
+/*
+ * ENTRY - declare entry point
+ */
+#define ENTRY(symbol)                           \
+	.globl  symbol;                         \
+	.align  2;                              \
+	.type   symbol, @function;              \
+symbol:
+
+/*
+ * END - mark end of function
+ */
+#define END(function)                           \
+	.size   function, . - function
+
+
+#endif				/* _MACHINE_ASM_H */
diff --git a/usr/klibc/SYSCALLS.def b/usr/klibc/SYSCALLS.def
index 64d7b0c1376665..8ebe8359a6c8f8 100644
--- a/usr/klibc/SYSCALLS.def
+++ b/usr/klibc/SYSCALLS.def
@@ -21,7 +21,7 @@ void _exit,exit::_exit(int);
 <?!ia64> pid_t clone::__clone(unsigned long, void *);
 <?ia64> pid_t clone::__clone2(unsigned long, void *, void *);
 # if ! _KLIBC_NO_MMU
-<!sparc,sparc64,ia64,arm64> pid_t fork();
+<!sparc,sparc64,ia64,arm64,riscv64> pid_t fork();
 <sparc,sparc64> pid_t fork@forkish();
 #endif
 #if _KLIBC_REAL_VFORK
diff --git a/usr/klibc/arch/riscv64/Kbuild b/usr/klibc/arch/riscv64/Kbuild
new file mode 100644
index 00000000000000..242ac5bbc6abee
--- /dev/null
+++ b/usr/klibc/arch/riscv64/Kbuild
@@ -0,0 +1,8 @@
+# -*- makefile -*-
+#
+# klibc files for riscv64
+
+always  := crt0.o
+targets := crt0.o
+
+klib-y := setjmp.o syscall.o
diff --git a/usr/klibc/arch/riscv64/MCONFIG b/usr/klibc/arch/riscv64/MCONFIG
new file mode 100644
index 00000000000000..38703d937e49d2
--- /dev/null
+++ b/usr/klibc/arch/riscv64/MCONFIG
@@ -0,0 +1,22 @@
+# -*- makefile -*-
+#
+# arch/riscv64/MCONFIG
+#
+# Special rules for this architecture.  Note that this is actually
+# included from the main Makefile, and that pathnames should be
+# accordingly.
+#
+
+# We should get klibc.so and the executables to agree on what gp
+# should be.  For now, disable gp-relative addressing.
+KLIBCLDFLAGS      = --no-relax
+KLIBCOPTFLAGS	  += -Os -fomit-frame-pointer
+ifeq ($(DEBUG),y)
+KLIBCOPTFLAGS     += -g
+endif
+KLIBCBITSIZE      = 64
+
+# Normal binaries start at 64 KB, so start the libary at 2 MB.
+KLIBCSHAREDFLAGS  =-Ttext 0x00200200
+
+KLIBCARCHINCFLAGS = -I$(KLIBCKERNELOBJ)/arch/riscv/include
diff --git a/usr/klibc/arch/riscv64/crt0.S b/usr/klibc/arch/riscv64/crt0.S
new file mode 100644
index 00000000000000..76fa3c2876f9a6
--- /dev/null
+++ b/usr/klibc/arch/riscv64/crt0.S
@@ -0,0 +1,22 @@
+#
+# arch/riscv64/crt0.S
+#
+# Does arch-specific initialization and invokes __libc_init
+# with the appropriate arguments.
+#
+# See __static_init.c or __shared_init.c for the expected
+# arguments.
+#
+
+#include <machine/asm.h>
+
+ENTRY(_start)
+	.option push
+	.option norelax
+	lla	gp, __global_pointer$
+	.option pop
+
+	mv	a0, sp			# Pointer to ELF entry structure
+	mv	a1, zero		# No onexit pointer
+	jal	__libc_init
+END(_start)
diff --git a/usr/klibc/arch/riscv64/setjmp.S b/usr/klibc/arch/riscv64/setjmp.S
new file mode 100644
index 00000000000000..66e009efa890e0
--- /dev/null
+++ b/usr/klibc/arch/riscv64/setjmp.S
@@ -0,0 +1,50 @@
+/*
+ * arch/riscv64/setjmp.S
+ *
+ * setjmp/longjmp for the RISC-V (RV64) architecture
+ *
+ * The jmp_buf is assumed to contain the following, in order:
+ *	pc (ra)
+ *	s0..s11
+ *	sp
+ */
+
+#include <machine/asm.h>
+
+ENTRY(setjmp)
+	sd	ra, 0(a0)
+	sd	s0, 8(a0)
+	sd	s1, 16(a0)
+	sd	s2, 24(a0)
+	sd	s3, 32(a0)
+	sd	s4, 40(a0)
+	sd	s5, 48(a0)
+	sd	s6, 56(a0)
+	sd	s7, 64(a0)
+	sd	s8, 72(a0)
+	sd	s9, 80(a0)
+	sd	s10, 88(a0)
+	sd	s11, 96(a0)
+	sd	sp, 104(a0)
+	mv	a0, zero
+	jr	ra
+END(setjmp)
+
+ENTRY(longjmp)
+	ld	ra, 0(a0)
+	ld	s0, 8(a0)
+	ld	s1, 16(a0)
+	ld	s2, 24(a0)
+	ld	s3, 32(a0)
+	ld	s4, 40(a0)
+	ld	s5, 48(a0)
+	ld	s6, 56(a0)
+	ld	s7, 64(a0)
+	ld	s8, 72(a0)
+	ld	s9, 80(a0)
+	ld	s10, 88(a0)
+	ld	s11, 96(a0)
+	ld	sp, 104(a0)
+	mv	a0, a1
+	jr	ra
+END(longjmp)
diff --git a/usr/klibc/arch/riscv64/syscall.S b/usr/klibc/arch/riscv64/syscall.S
new file mode 100644
index 00000000000000..89d9bd2f923f29
--- /dev/null
+++ b/usr/klibc/arch/riscv64/syscall.S
@@ -0,0 +1,13 @@
+#include <machine/asm.h>
+#include <asm/unistd.h>
+
+ENTRY(__syscall_common)
+	scall
+	li	t0, -4096
+	bleu	a0, t0, 1f
+	neg	a0, a0
+	lui	t0, %hi(errno)
+	sw	a0, %lo(errno)(t0)
+	li	a0, -1
+1:	jr	ra
+END(__syscall_common)
diff --git a/usr/klibc/arch/riscv64/sysstub.ph b/usr/klibc/arch/riscv64/sysstub.ph
new file mode 100644
index 00000000000000..85c1beb89e92c1
--- /dev/null
+++ b/usr/klibc/arch/riscv64/sysstub.ph
@@ -0,0 +1,26 @@
+# -*- perl -*-
+#
+# arch/riscv/sysstub.ph
+#
+# Script to generate system call stubs
+#
+
+# On RISC-V, most system calls follow the standard convention, with the
+# system call number in x17 (a7) and the return value in x10 (a0).
+
+sub make_sysstub($$$$$@) {
+    my($outputdir, $fname, $type, $sname, $stype, @args) = @_;
+
+    $stype = $stype || 'common';
+    open(OUT, '>', "${outputdir}/${fname}.S");
+    print OUT "#include <machine/asm.h>\n";
+    print OUT "#include <asm/unistd.h>\n";
+    print OUT "\n";
+    print OUT "ENTRY(${fname})\n";
+    print OUT "\tli\ta7, __NR_${sname}\n";
+    print OUT "\tj\t__syscall_${stype}\n";
+    print OUT "END(${fname})\n";
+    close(OUT);
+}
+
+1;