[PATCH v2 4/6] objtool/powerpc: Skip jump destination analysis and unnanotated intra-function call warnings for --ftr-fixup

[Shivang Upadhyay <shivangu@linux.ibm.com>]

From: Sathvika Vasireddy <sv@linux.ibm.com>

Objtool is throwing unannotated intra-function call warnings
when run on vmlinux with --ftr-fixup option.

One such example:

vmlinux: warning: objtool: .text+0x3d94:
                        unannotated intra-function call

.text + 0x3d94 = c000000000008000 + 3d94 = c0000000000081d4

c0000000000081d4: 45 24 02 48  bl c00000000002a618
<system_reset_exception+0x8>

c00000000002a610 <system_reset_exception>:
c00000000002a610:       0e 01 4c 3c     addis   r2,r12,270
                        c00000000002a610: R_PPC64_REL16_HA    .TOC.
c00000000002a614:       f0 6c 42 38     addi    r2,r2,27888
                        c00000000002a614: R_PPC64_REL16_LO    .TOC.+0x4
c00000000002a618:       a6 02 08 7c     mflr    r0

This is happening because we should be looking for destination
symbols that are at absolute offsets instead of relative offsets.
After fixing dest_off to point to absolute offset, there are still
a lot of these warnings shown.

In the above example, objtool is computing the destination
offset to be c00000000002a618, which points to a completely
different instruction. find_call_destination() is looking for this
offset and failing. Instead, we should be looking for destination
offset c00000000002a610 which points to system_reset_exception
function.

Even after fixing the way destination offset is computed, and
after looking for dest_off - 0x8 in cases where the original offset
is not found, there are still a lot of unannotated intra-function
call warnings generated. This is due to symbols that are not
properly annotated.

So, for now, as a hack to curb these warnings, do not emit
unannotated intra-function call warnings when objtool is run
with --ftr-fixup option.

Skip add_jump_destinations() and suppress intra-function call
errors in --ftr-fixup mode. The feature fixup pass only needs fixup
entry tables, relocation entries from .__ftr_alternates.text, and
elf_write_insn() to patch branch offsets.

Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Shivang Upadhyay <shivangu@linux.ibm.com>
---
 tools/objtool/check.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7662e990cb13..907dbc8f9b71 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1693,8 +1693,11 @@ static int add_call_destinations(struct objtool_file *file)
 				continue;
 
 			if (!insn_call_dest(insn)) {
-				ERROR_INSN(insn, "unannotated intra-function call");
-				return -1;
+				if (!opts.ftr_fixup) {
+					ERROR_INSN(insn, "unannotated intra-function call");
+					return -1;
+				}
+				continue;
 			}
 
 			if (func && !is_func_sym(insn_call_dest(insn))) {
@@ -2661,8 +2664,10 @@ int decode_file(struct objtool_file *file)
 			return -1;
 	}
 
-	if (add_jump_destinations(file))
-		return -1;
+	if (!opts.ftr_fixup) {
+		if (add_jump_destinations(file))
+			return -1;
+	}
 
 	/*
 	 * Must be before add_call_destination(); it changes INSN_CALL to
-- 
2.54.0