[PATCH v2 01/10] powerpc/lib: Add helper to check if offset is within conditional branch range

From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	Jordan Niethe <jniethe5@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Johan Almbladh <johan.almbladh@anyfinetworks.com>,
	Song Liu <songliubraving@fb.com>
Cc: <bpf@vger.kernel.org>, <linuxppc-dev@lists.ozlabs.org>
Subject: [PATCH v2 01/10] powerpc/lib: Add helper to check if offset is within conditional branch range
Date: Wed,  6 Oct 2021 01:55:20 +0530	[thread overview]
Message-ID: <442b69a34ced32ca346a0d9a855f3f6cfdbbbd41.1633464148.git.naveen.n.rao@linux.vnet.ibm.com> (raw)
In-Reply-To: <cover.1633464148.git.naveen.n.rao@linux.vnet.ibm.com>

Add a helper to check if a given offset is within the branch range for a
powerpc conditional branch instruction, and update some sites to use the
new helper.

Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
Changelog:
- Change 0x7FFF to 0x7fff, per Christophe


 arch/powerpc/include/asm/code-patching.h | 1 +
 arch/powerpc/lib/code-patching.c         | 7 ++++++-
 arch/powerpc/net/bpf_jit.h               | 7 +------
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index a95f63788c6b14..4ba834599c4d4c 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -23,6 +23,7 @@
 #define BRANCH_ABSOLUTE	0x2
 
 bool is_offset_in_branch_range(long offset);
+bool is_offset_in_cond_branch_range(long offset);
 int create_branch(struct ppc_inst *instr, const u32 *addr,
 		  unsigned long target, int flags);
 int create_cond_branch(struct ppc_inst *instr, const u32 *addr,
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index f9a3019e37b43c..c5ed9882383521 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -228,6 +228,11 @@ bool is_offset_in_branch_range(long offset)
 	return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
 }
 
+bool is_offset_in_cond_branch_range(long offset)
+{
+	return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
+}
+
 /*
  * Helper to check if a given instruction is a conditional branch
  * Derived from the conditional checks in analyse_instr()
@@ -280,7 +285,7 @@ int create_cond_branch(struct ppc_inst *instr, const u32 *addr,
 		offset = offset - (unsigned long)addr;
 
 	/* Check we can represent the target in the instruction format */
-	if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
+	if (!is_offset_in_cond_branch_range(offset))
 		return 1;
 
 	/* Mask out the flags and target, so they don't step on each other. */
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 99fad093f43ec1..935ea95b66359e 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -78,11 +78,6 @@
 #define PPC_FUNC_ADDR(d,i) do { PPC_LI32(d, i); } while(0)
 #endif
 
-static inline bool is_nearbranch(int offset)
-{
-	return (offset < 32768) && (offset >= -32768);
-}
-
 /*
  * The fly in the ointment of code size changing from pass to pass is
  * avoided by padding the short branch case with a NOP.	 If code size differs
@@ -91,7 +86,7 @@ static inline bool is_nearbranch(int offset)
  * state.
  */
 #define PPC_BCC(cond, dest)	do {					      \
-		if (is_nearbranch((dest) - (ctx->idx * 4))) {		      \
+		if (is_offset_in_cond_branch_range((long)(dest) - (ctx->idx * 4))) {	\
 			PPC_BCC_SHORT(cond, dest);			      \
 			EMIT(PPC_RAW_NOP());				      \
 		} else {						      \
-- 
2.33.0

