[glibc/release/2.38/master] sparc: Remove unwind information from signal return stubs [BZ #31244]

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=0c5e5bace57578ed3e28eb89ee2d2b31b74c4ecc

commit 0c5e5bace57578ed3e28eb89ee2d2b31b74c4ecc
Author: Daniel Cederman <cederman@gaisler.com>
Date:   Tue Jan 16 09:31:41 2024 +0100

    sparc: Remove unwind information from signal return stubs [BZ #31244]
    
    The functions were previously written in C, but were not compiled
    with unwind information. The ENTRY/END macros includes .cfi_startproc
    and .cfi_endproc which adds unwind information. This caused the
    tests cleanup-8 and cleanup-10 in the GCC testsuite to fail.
    This patch adds a version of the ENTRY/END macros without the
    CFI instructions that can be used instead.
    
    sigaction registers a restorer address that is located two instructions
    before the stub function. This patch adds a two instruction padding to
    avoid that the unwinder accesses the unwind information from the function
    that the linker has placed right before it in memory. This fixes an issue
    with pthread_cancel that caused tst-mutex8-static (and other tests) to fail.
    
    Signed-off-by: Daniel Cederman <cederman@gaisler.com>
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
    (cherry picked from commit 7bd06985c0a143cdcba2762bfe020e53514a53de)

Diff:
---
 sysdeps/sparc/sysdep.h                                 |  9 +++++++++
 sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S | 11 +++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/sysdeps/sparc/sysdep.h b/sysdeps/sparc/sysdep.h
index 687e626182..151baa5e10 100644
--- a/sysdeps/sparc/sysdep.h
+++ b/sysdeps/sparc/sysdep.h
@@ -76,6 +76,15 @@ C_LABEL(name)				\
 	cfi_endproc;			\
 	.size name, . - name
 
+#define ENTRY_NOCFI(name)			\
+	.align	4;			\
+	.global	C_SYMBOL_NAME(name);	\
+	.type	name, @function;	\
+C_LABEL(name)
+
+#define END_NOCFI(name)			\
+	.size name, . - name
+
 #undef LOC
 #define LOC(name)  .L##name
 
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S b/sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S
index cf509c8d5c..1962f9053c 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/sigreturn_stub.S
@@ -23,12 +23,15 @@
 
    [1] https://lkml.org/lkml/2016/5/27/465  */
 
-ENTRY (__rt_sigreturn_stub)
+	nop
+	nop
+
+ENTRY_NOCFI (__rt_sigreturn_stub)
 	mov	__NR_rt_sigreturn, %g1
 	ta	0x10
-END (__rt_sigreturn_stub)
+END_NOCFI (__rt_sigreturn_stub)
 
-ENTRY (__sigreturn_stub)
+ENTRY_NOCFI (__sigreturn_stub)
 	mov	__NR_sigreturn, %g1
 	ta	0x10
-END (__sigreturn_stub)
+END_NOCFI (__sigreturn_stub)