guix: patch around riscv issue with newer (2.40+) binutils

See https://sourceware.org/bugzilla/show_bug.cgi?id=28509.
https://sourceware.org/git/?p=glibc.git;a=commit;h=68389203832ab39dd0dbaabbc4059e7fff51c29b.

Needed for the next commit, which bumps the time-machine.

contrib/guix/manifest.scm

@@ -466,7 +466,8 @@ inspecting signatures in Mach-O binaries.")
               (sha256
                (base32
                 "017qdpr5id7ddb4lpkzj2li1abvw916m3fc6n7nw28z4h5qbv2n0"))
-              (patches (search-our-patches "glibc-guix-prefix.patch"))))
+              (patches (search-our-patches "glibc-guix-prefix.patch"
+                                           "glibc-riscv-jumptarget.patch"))))
     (arguments
       (substitute-keyword-arguments (package-arguments glibc)
         ((#:configure-flags flags)

contrib/guix/patches/glibc-riscv-jumptarget.patch

@@ -0,0 +1,57 @@
+commit 68389203832ab39dd0dbaabbc4059e7fff51c29b
+Author: Fangrui Song <maskray@google.com>
+Date:   Thu Oct 28 11:39:49 2021 -0700
+
+    riscv: Fix incorrect jal with HIDDEN_JUMPTARGET
+    
+    A non-local STV_DEFAULT defined symbol is by default preemptible in a
+    shared object. j/jal cannot target a preemptible symbol. On other
+    architectures, such a jump instruction either causes PLT [BZ #18822], or
+    if short-ranged, sometimes rejected by the linker (but not by GNU ld's
+    riscv port [ld PR/28509]).
+    
+    Use HIDDEN_JUMPTARGET to target a non-preemptible symbol instead.
+    
+    With this patch, ld.so and libc.so can be linked with LLD if source
+    files are compiled/assembled with -mno-relax/-Wa,-mno-relax.
+    
+    Acked-by: Palmer Dabbelt <palmer@dabbelt.com>
+    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+Can be dropped when we are using glibc 2.35 or later.
+
+diff --git a/sysdeps/riscv/setjmp.S b/sysdeps/riscv/setjmp.S
+index 0b92016b31..bec7ff80f4 100644
+--- a/sysdeps/riscv/setjmp.S
++++ b/sysdeps/riscv/setjmp.S
+@@ -21,7 +21,7 @@
+ 
+ ENTRY (_setjmp)
+   li	a1, 0
+-  j	__sigsetjmp
++  j	HIDDEN_JUMPTARGET (__sigsetjmp)
+ END (_setjmp)
+ ENTRY (setjmp)
+   li	a1, 1
+diff --git a/sysdeps/unix/sysv/linux/riscv/setcontext.S b/sysdeps/unix/sysv/linux/riscv/setcontext.S
+index 9510518750..e44a68aad4 100644
+--- a/sysdeps/unix/sysv/linux/riscv/setcontext.S
++++ b/sysdeps/unix/sysv/linux/riscv/setcontext.S
+@@ -95,6 +95,7 @@ LEAF (__setcontext)
+ 99:	j	__syscall_error
+ 
+ END (__setcontext)
++libc_hidden_def (__setcontext)
+ weak_alias (__setcontext, setcontext)
+ 
+ LEAF (__start_context)
+@@ -108,7 +109,7 @@ LEAF (__start_context)
+ 	/* Invoke subsequent context if present, else exit(0).  */
+ 	mv	a0, s2
+ 	beqz	s2, 1f
+-	jal	__setcontext
+-1:	j	exit
++	jal	HIDDEN_JUMPTARGET (__setcontext)
++1:	j	HIDDEN_JUMPTARGET (exit)
+ 
+ END (__start_context)