linux-kernel - [PATCH v4 2/4] objtool/powerpc: Add support for decoding all types of uncond branches

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Message-ID: <0ca71a4b0ac679ea52bd9fdd1f607195d72b499f.1733245362.git.christophe.leroy@csgroup.eu>
Date: Tue,  3 Dec 2024 20:44:50 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Jason Baron <jbaron@...mai.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v4 2/4] objtool/powerpc: Add support for decoding all types of uncond branches

Add support for 'bla' instruction.

This is done by 'flagging' the address as an absolute address so that
arch_jump_destination() can calculate it as expected. Because code is
_always_ 4 bytes aligned, use bit 30 as flag.

Also add support for 'b' and 'ba' instructions. Objtool call them jumps.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 tools/objtool/arch/powerpc/decode.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
index 53b55690f320..c1228fef3dec 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -55,12 +55,15 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
 
 	switch (opcode) {
 	case 18: /* b[l][a] */
-		if ((ins & 3) == 1) /* bl */
+		if (ins & 1)	/* bl[a] */
 			typ = INSN_CALL;
+		else		/* b[a] */
+			typ = INSN_JUMP_UNCONDITIONAL;
 
 		imm = ins & 0x3fffffc;
 		if (imm & 0x2000000)
 			imm -= 0x4000000;
+		imm |= ins & 2;	/* AA flag */
 		break;
 	}
 
@@ -77,6 +80,9 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
 
 unsigned long arch_jump_destination(struct instruction *insn)
 {
+	if (insn->immediate & 2)
+		return insn->immediate & ~2;
+
 	return insn->offset + insn->immediate;
 }
 
-- 
2.47.0