RISC-V updates for v5.5-rc4

One important fix for RISC-V:
 
 - Redirect any incoming syscall with an ID less than -1 to
   sys_ni_syscall, rather than allowing them to fall through into the
   syscall handler.
 
 and two minor build fixes:
 
 - Export __asm_copy_{from,to}_user() from where they are defined.
   This fixes a build error triggered by some randconfigs.
 
 - Export flush_icache_all().  I'd resisted this before, since
   historically we didn't want modules to be able to flush the I$
   directly; but apparently everyone else is doing it now.
 -----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCgAdFiEElRDoIDdEz9/svf2Kx4+xDQu9KksFAl4I3wIACgkQx4+xDQu9
 KksKWw/+LzcBZ1/H2IzXqFdnu8nloBv86t60s9ZPTDFDpqFZ5JnxnhB1z9XU3mnS
 q8u4tWMMMEyT3iPByDPIMr3wdEjtPK2kqeMmkpo6o6zkTzcc0zk4Q5h8JcPZjD2q
 RFuNlfboEz5JHdQXNaV4mP+mW4RqxxJDZx11Zspj1g1v2bWOeRDc5bn0GUQGl4Jg
 uaP+5/lnuZ2ad0rXoMT2ycnDmpZ7Btriv2vbjfZFuWTBqElJsynA+7szagWqF1bR
 1cFKbocpECKqvIKlMHdBAxMaqs25YuiU+i5KrKst6k4m1O8SthsK4iXn1CVmC+RL
 R77p0yQRGnrSf/AHWRZfAEjwZlOvDHsAg4U0/nPw4SPutuquzf76pZllBQKXgJqx
 30oJammVveO3rOsNM4tsydpLGgs8M85XBfkmECeiWNhP7+RPsihHKdbXdCrBaESR
 a+bij81L8MfMbGhwAsSUiH3upq0CvsMw8pSPCZWQ2jaxbN5tgcFw3qSkfKC5STDj
 1k8DpeHNnxnR1lC/xSOR89I3gUot4Y4nw5awZP6kngB7sRTG8TRL5eh5mwQKtRFV
 5h4jyh+d0p4fiAVTzr/YjWrYWRs6318La+CRwhIOevKcAuOESVOwyeM9PRlTAxPh
 il59toaL+6KOtAaSacc0gt/+lv/g4Kd8MD/QU1viG/Da6zqkCK4=
 =y3/O
 -----END PGP SIGNATURE-----

Merge tag 'riscv/for-v5.5-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Paul Walmsley:
 "One important fix for RISC-V:

   - Redirect any incoming syscall with an ID less than -1 to
     sys_ni_syscall, rather than allowing them to fall through into the
     syscall handler.

  and two minor build fixes:

   - Export __asm_copy_{from,to}_user() from where they are defined.
     This fixes a build error triggered by some randconfigs.

   - Export flush_icache_all(). I'd resisted this before, since
     historically we didn't want modules to be able to flush the I$
     directly; but apparently everyone else is doing it now"

* tag 'riscv/for-v5.5-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: export flush_icache_all to modules
  riscv: reject invalid syscalls below -1
  riscv: fix compile failure with EXPORT_SYMBOL() & !MMU

arch/riscv/kernel/entry.S

@@ -246,6 +246,7 @@ check_syscall_nr:
 	 */
 	li t1, -1
 	beq a7, t1, ret_from_syscall_rejected
+	blt a7, t1, 1f
 	/* Call syscall */
 	la s0, sys_call_table
 	slli t0, a7, RISCV_LGPTR

arch/riscv/kernel/riscv_ksyms.c

@@ -9,8 +9,5 @@
 /*
  * Assembly functions that may be used (directly or indirectly) by modules
  */
-EXPORT_SYMBOL(__clear_user);
-EXPORT_SYMBOL(__asm_copy_to_user);
-EXPORT_SYMBOL(__asm_copy_from_user);
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memcpy);

arch/riscv/lib/uaccess.S

@@ -1,4 +1,5 @@
 #include <linux/linkage.h>
+#include <asm-generic/export.h>
 #include <asm/asm.h>
 #include <asm/csr.h>
 
@@ -66,6 +67,8 @@ ENTRY(__asm_copy_from_user)
 	j 3b
 ENDPROC(__asm_copy_to_user)
 ENDPROC(__asm_copy_from_user)
+EXPORT_SYMBOL(__asm_copy_to_user)
+EXPORT_SYMBOL(__asm_copy_from_user)
 
 
 ENTRY(__clear_user)
@@ -108,6 +111,7 @@ ENTRY(__clear_user)
 	bltu a0, a3, 5b
 	j 3b
 ENDPROC(__clear_user)
+EXPORT_SYMBOL(__clear_user)
 
 	.section .fixup,"ax"
 	.balign 4

arch/riscv/mm/cacheflush.c

@@ -22,6 +22,7 @@ void flush_icache_all(void)
 	else
 		on_each_cpu(ipi_remote_fence_i, NULL, 1);
 }
+EXPORT_SYMBOL(flush_icache_all);
 
 /*
  * Performs an icache flush for the given MM context.  RISC-V has no direct