runtime: add support for --buildmode=c-shared on loong64

These c-shared related CLs are follow up of CLs 455016, 455017, 455018. Here we
follow the LoongArch ELF psABI v2 standard, which requires the support of the
PCALAU12I instruction.

Updates #53301
Updates #58784

Change-Id: I7f1ddbf3b2470d610f12069d147aa9b3a6a96f32
Reviewed-on: https://go-review.googlesource.com/c/go/+/425474
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/runtime/rt0_linux_loong64.s b/src/runtime/rt0_linux_loong64.s
index b9aaa510e179bf7cd9a4d9094927d13b8242d930..b52f7d530a6a9806143c46ffd3bc9d903fa7f06e 100644 (file)
--- a/src/runtime/rt0_linux_loong64.s
+++ b/src/runtime/rt0_linux_loong64.s
@@ -3,6 +3,7 @@
 // license that can be found in the LICENSE file.
 
 #include "textflag.h"
+#include "cgo/abi_loong64.h"
 
 TEXT _rt0_loong64_linux(SB),NOSPLIT|NOFRAME,$0
        // In a statically linked binary, the stack contains argc,
@@ -13,6 +14,56 @@ TEXT _rt0_loong64_linux(SB),NOSPLIT|NOFRAME,$0
        ADDV    $8, R3, R5      // argv
        JMP     main(SB)
 
+// When building with -buildmode=c-shared, this symbol is called when the shared
+// library is loaded.
+TEXT _rt0_loong64_linux_lib(SB),NOSPLIT,$168
+       // Preserve callee-save registers.
+       SAVE_R22_TO_R31(3*8)
+       SAVE_F24_TO_F31(13*8)
+
+       // Initialize g as nil in case of using g later e.g. sigaction in cgo_sigaction.go
+       MOVV    R0, g
+
+       MOVV    R4, _rt0_loong64_linux_lib_argc<>(SB)
+       MOVV    R5, _rt0_loong64_linux_lib_argv<>(SB)
+
+       // Synchronous initialization.
+       MOVV    $runtime·libpreinit(SB), R19
+       JAL     (R19)
+
+       // Create a new thread to do the runtime initialization and return.
+       MOVV    _cgo_sys_thread_create(SB), R19
+       BEQ     R19, nocgo
+       MOVV    $_rt0_loong64_linux_lib_go(SB), R4
+       MOVV    $0, R5
+       JAL     (R19)
+       JMP     restore
+
+nocgo:
+       MOVV    $0x800000, R4                     // stacksize = 8192KB
+       MOVV    $_rt0_loong64_linux_lib_go(SB), R5
+       MOVV    R4, 8(R3)
+       MOVV    R5, 16(R3)
+       MOVV    $runtime·newosproc0(SB), R19
+       JAL     (R19)
+
+restore:
+       // Restore callee-save registers.
+       RESTORE_R22_TO_R31(3*8)
+       RESTORE_F24_TO_F31(13*8)
+       RET
+
+TEXT _rt0_loong64_linux_lib_go(SB),NOSPLIT,$0
+       MOVV    _rt0_loong64_linux_lib_argc<>(SB), R4
+       MOVV    _rt0_loong64_linux_lib_argv<>(SB), R5
+       MOVV    $runtime·rt0_go(SB),R19
+       JMP     (R19)
+
+DATA _rt0_loong64_linux_lib_argc<>(SB)/8, $0
+GLOBL _rt0_loong64_linux_lib_argc<>(SB),NOPTR, $8
+DATA _rt0_loong64_linux_lib_argv<>(SB)/8, $0
+GLOBL _rt0_loong64_linux_lib_argv<>(SB),NOPTR, $8
+
 TEXT main(SB),NOSPLIT|NOFRAME,$0
        // in external linking, glibc jumps to main with argc in R4
        // and argv in R5