[PATCH] RISC-V: Allow long jumps to __syscall_error

["Łukasz Stelmach" <l.stelmach@samsung.com>]

__syscall_error may end up farther than 1MiB away from a caller,
especially when linking statically large binaries. la+jr allow for
4GiB jumps.

Fixes: 36960f0c76 ("RISC-V: Linux Syscall Interface")
Fixes: 7f33b09c65 ("RISC-V: Linux ABI")
Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
---

I was compiling and statically linking GNU Guile and I was getting a
lot of messages like this:

    /usr/lib64/libc.a(uname.o): in function `__uname':
    (.text+0x10): relocation truncated to fit: R_RISCV_JAL against symbol `__syscall_error' defined in .text section in /usr/lib64/libc.a(sysdep.o)

And indeed in uname.o there was a relative jump which was marked as
R_RISCV_JAL and pointed to __syscall_error. After sucessfully linking
the binary with this fix applied __uname and __syscall_error end up
1125000 bytes apart.

--8<---------------cut here---------------end--------------->8---
Relocation section '.rela.text' at offset 0x250 contains 4 entries:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
000000000000  00000000002b R_RISCV_ALIGN                        2
000000000002  00000000002b R_RISCV_ALIGN                        2
00000000000e  000a00000010 R_RISCV_BRANCH    0000000000000014 .Lsyscall_error__uname + 0
000000000014  000c00000011 R_RISCV_JAL       0000000000000000 __syscall_error + 0
--8<---------------cut here---------------end--------------->8---

--8<---------------cut here---------------end--------------->8---
uname.o:     file format elf64-littleriscv


Disassembly of section .text:

0000000000000000 <$x>:
   0:   0001                    nop
   2:   0001                    nop

0000000000000004 <__uname>:
   4:   0a000893                li      a7,160
   8:   00000073                ecall
   c:   78fd                    lui     a7,0xfffff
   e:   00a8e363                bltu    a7,a0,14 <.Lsyscall_error__uname>
  12:   8082                    ret

0000000000000014 <.Lsyscall_error__uname>:
  14:   fedff06f                j       0 <$x>
 ^^^^                           ^^^^^^^^^^^^^^
  18:   8082                    ret
        ...
--8<---------------cut here---------------end--------------->8---

I suspect the two nops that the jump points to were meant(?)/could(??) be
used (if there were more of them) to be a placeholder for a longer
jump. Alas binutils 2.38 can't handle it properly (yet?), so a manual
intervention here seems reasonable.

I have neither seen any errors regarding code in *context.S and vfork.S
files nor tested if the altered code works, but I assume it needs to be
fixed as well.

 sysdeps/unix/sysv/linux/riscv/clone.S       | 3 ++-
 sysdeps/unix/sysv/linux/riscv/getcontext.S  | 3 ++-
 sysdeps/unix/sysv/linux/riscv/setcontext.S  | 3 ++-
 sysdeps/unix/sysv/linux/riscv/swapcontext.S | 3 ++-
 sysdeps/unix/sysv/linux/riscv/sysdep.h      | 3 ++-
 sysdeps/unix/sysv/linux/riscv/vfork.S       | 3 ++-
 6 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/riscv/clone.S b/sysdeps/unix/sysv/linux/riscv/clone.S
index d7d2915e87..e716285afa 100644
--- a/sysdeps/unix/sysv/linux/riscv/clone.S
+++ b/sysdeps/unix/sysv/linux/riscv/clone.S
@@ -63,7 +63,8 @@ L (invalid):
 	li		a0, -EINVAL
 	/* Something bad happened -- no child created.  */
 L (error):
-	j		__syscall_error
+	la		t0, __syscall_error
+	jr		t0
 	END (__clone)
 
 /* Load up the arguments to the function.  Put this block of code in
diff --git a/sysdeps/unix/sysv/linux/riscv/getcontext.S b/sysdeps/unix/sysv/linux/riscv/getcontext.S
index 499f70b65d..a4751ae595 100644
--- a/sysdeps/unix/sysv/linux/riscv/getcontext.S
+++ b/sysdeps/unix/sysv/linux/riscv/getcontext.S
@@ -70,7 +70,8 @@ LEAF (__getcontext)
 
 	ret
 
-99:	j	__syscall_error
+99:	la	t0, __syscall_error
+	jr	t0
 
 PSEUDO_END (__getcontext)
 
diff --git a/sysdeps/unix/sysv/linux/riscv/setcontext.S b/sysdeps/unix/sysv/linux/riscv/setcontext.S
index e3bc84a2e6..fddd9d843f 100644
--- a/sysdeps/unix/sysv/linux/riscv/setcontext.S
+++ b/sysdeps/unix/sysv/linux/riscv/setcontext.S
@@ -92,7 +92,8 @@ LEAF (__setcontext)
 
 	jr	t1
 
-99:	j	__syscall_error
+99:	la	t0, __syscall_error
+	jr	t0
 
 END (__setcontext)
 libc_hidden_def (__setcontext)
diff --git a/sysdeps/unix/sysv/linux/riscv/swapcontext.S b/sysdeps/unix/sysv/linux/riscv/swapcontext.S
index 4da615f6d4..8e29d96595 100644
--- a/sysdeps/unix/sysv/linux/riscv/swapcontext.S
+++ b/sysdeps/unix/sysv/linux/riscv/swapcontext.S
@@ -118,7 +118,8 @@ LEAF (__swapcontext)
 	jr	t1
 
 
-99:	j	__syscall_error
+99:	la	t0, __syscall_error
+	jr	t0
 
 PSEUDO_END (__swapcontext)
 
diff --git a/sysdeps/unix/sysv/linux/riscv/sysdep.h b/sysdeps/unix/sysv/linux/riscv/sysdep.h
index 37ff07a0d7..0cd78daf2b 100644
--- a/sysdeps/unix/sysv/linux/riscv/sysdep.h
+++ b/sysdeps/unix/sysv/linux/riscv/sysdep.h
@@ -102,7 +102,8 @@
 # else
 #  define SYSCALL_ERROR_HANDLER(name)				\
 .Lsyscall_error ## name:					\
-        j       __syscall_error;
+        la t0, __syscall_error;					\
+        jr t0;
 # endif
 
 /* Performs a system call, not setting errno.  */
diff --git a/sysdeps/unix/sysv/linux/riscv/vfork.S b/sysdeps/unix/sysv/linux/riscv/vfork.S
index 0970543619..8f1b2c9b3a 100644
--- a/sysdeps/unix/sysv/linux/riscv/vfork.S
+++ b/sysdeps/unix/sysv/linux/riscv/vfork.S
@@ -39,7 +39,8 @@ LEAF (__libc_vfork)
 	bltz	a0, 1f
 	ret
 
-1:	j		__syscall_error
+1:	la	t0, __syscall_error
+	jr	t0
 END (__libc_vfork)
 
 weak_alias (__libc_vfork, vfork)
-- 
2.30.2