Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation

On Wed, Aug 31, 2022 at 12:50:07PM +0000, Christophe Leroy wrote:

Le 29/08/2022 à 07:52, Sathvika Vasireddy a écrit :

quoted

+	opcode = insn >> 26;
+
+	switch (opcode) {
+	case 18: /* bl */

case 18 is more than 'bl', it includes also 'b'.
In both cases, the calculation of *immediate is the same.

It also is "ba" and "bla", sometimes written as "b[l][a]".

It would therefore be more correct to perform the calculation and setup 
of *immediate outside the 'if ((insn & 3) == 1)', that would avoid 
unnecessary churn the day we add support for branches without link.

quoted

+		if ((insn & 3) == 1) {
+			*type = INSN_CALL;
+			*immediate = insn & 0x3fffffc;
+			if (*immediate & 0x2000000)
+				*immediate -= 0x4000000;
+		}
+		break;
+	}

Does this handle AA=1 correctly at all?  That is valid both with and
without relocations, just like AA=0.  Same for AA=1 LK=0 btw.

If you only handle AA=0, the code should explicitly test for that.


Segher