[PATCH 3/4] s390/bpf: Serialize text patching with text_mutex

[Heiko Carstens <hca@linux.ibm.com>]

Acquire text_mutex in bpf_arch_text_poke(). This way s390 uses text_mutex
like most other architectures.

This is a prereq for removing the spinlock in __s390_kernel_write().

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/net/bpf_jit_comp.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 51db92c3329d..b8ff1ca2f598 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -22,6 +22,7 @@
 #include <linux/init.h>
 #include <linux/bpf.h>
 #include <linux/cfi.h>
+#include <linux/memory.h>
 #include <linux/mm.h>
 #include <linux/kernel.h>
 #include <asm/cacheflush.h>
@@ -2446,9 +2447,9 @@ bool bpf_jit_supports_far_kfunc_call(void)
 	return true;
 }
 
-int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
-		       enum bpf_text_poke_type new_t, void *old_addr,
-		       void *new_addr)
+static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
+				enum bpf_text_poke_type new_t, void *old_addr,
+				void *new_addr)
 {
 	struct bpf_plt expected_plt, current_plt, new_plt, *plt;
 	struct {
@@ -2458,6 +2459,8 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
 	char *ret;
 	int err;
 
+	guard(mutex)(&text_mutex);
+
 	/* Verify the branch to be patched. */
 	err = copy_from_kernel_nofault(&insn, ip, sizeof(insn));
 	if (err < 0)
@@ -2491,10 +2494,20 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
 	/* Adjust the mask of the branch. */
 	insn.opc = 0xc004 | (new_addr ? 0xf0 : 0);
 	s390_kernel_write((char *)ip + 1, (char *)&insn.opc + 1, 1);
+	return 0;
+}
 
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,
+		       enum bpf_text_poke_type new_t, void *old_addr,
+		       void *new_addr)
+{
+	int err;
+
+	err = __bpf_arch_text_poke(ip, old_t, new_t, old_addr, new_addr);
+	if (err)
+		return err;
 	/* Make the new code visible to the other CPUs. */
 	text_poke_sync_lock();
-
 	return 0;
 }
 
-- 
2.53.0