[glibc] ARC: run child from the separate start block in __clone

[glibc] ARC: run child from the separate start block in __clone

[Pavel Kozlov]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=447273e0bf22a3d42e05e6b16d309f3f89879bea

commit 447273e0bf22a3d42e05e6b16d309f3f89879bea
Author: Pavel Kozlov <pavel.kozlov@synopsys.com>
Date:   Thu Mar 2 20:10:19 2023 +0400

    ARC: run child from the separate start block in __clone
    
    For better debug experience use separate code block with extra
    cfi_* directives to run child (same as in __clone3).
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 sysdeps/unix/sysv/linux/arc/clone.S | 40 +++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/arc/clone.S b/sysdeps/unix/sysv/linux/arc/clone.S
index 7666496256..0029aaeb81 100644
--- a/sysdeps/unix/sysv/linux/arc/clone.S
+++ b/sysdeps/unix/sysv/linux/arc/clone.S
@@ -20,9 +20,6 @@
 #include <sysdep.h>
 #define _ERRNO_H	1
 #include <bits/errno.h>
-#include <tcb-offsets.h>
-
-#define CLONE_SETTLS		0x00080000
 
 /* int clone(int (*fn)(void *), void *child_stack,
            int flags, void *arg, ...
@@ -63,19 +60,9 @@ ENTRY (__clone)
 	ARC_TRAP_INSN
 
 	cmp	r0, 0		/* return code : 0 new process, !0 parent.  */
+	beq	thread_start_clone
 	blt	L (__sys_err2)	/* < 0 (signed) error.  */
-	jnz	[blink]		/* Parent returns.  */
-
-	/* child jumps off to @fn with @arg as argument
-           TP register already set by kernel.  */
-	jl.d	[r10]
-	mov	r0, r11
-
-	/* exit() with result from @fn (already in r0).  */
-	mov	r8, __NR_exit
-	ARC_TRAP_INSN
-	/* In case it ever came back.  */
-	flag	1
+	j	[blink]		/* Parent returns.  */
 
 L (__sys_err):
 	mov	r0, -EINVAL
@@ -89,5 +76,28 @@ L (__sys_err2):
 	       position independent.  */
 	b   __syscall_error
 PSEUDO_END (__clone)
+
+
+	.align 4
+	.type thread_start_clone, %function
+thread_start_clone:
+	cfi_startproc
+	/* Terminate call stack by noting ra is undefined.  */
+	cfi_undefined (blink)
+
+	/* Child jumps off to @fn with @arg as argument.  */
+	jl.d	[r10]
+	mov	r0, r11
+
+	/* exit() with result from @fn (already in r0).  */
+	mov	r8, __NR_exit
+	ARC_TRAP_INSN
+
+	/* In case it ever came back.  */
+	flag	1
+
+	cfi_endproc
+	.size thread_start_clone, .-thread_start_clone
+
 libc_hidden_def (__clone)
 weak_alias (__clone, clone)