linux-kernel - [RFC PATCH v3 01/15] objtool: Make validate_call() recognize indirect calls to pv

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Message-ID: <20241119153502.41361-2-vschneid@redhat.com>
Date: Tue, 19 Nov 2024 16:34:48 +0100
From: Valentin Schneider <vschneid@...hat.com>
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Subject: [RFC PATCH v3 01/15] objtool: Make validate_call() recognize indirect calls to pv_ops[]

call_dest_name() does not get passed the file pointer of validate_call(),
which means its invocation of insn_reloc() will always return NULL. Make it
take a file pointer.

While at it, make sure call_dest_name() uses arch_dest_reloc_offset(),
otherwise it gets the pv_ops[] offset wrong.

Fabricating an intentional warning shows the change; previously:

  vmlinux.o: warning: objtool: __flush_tlb_all_noinstr+0x4: call to {dynamic}() leaves .noinstr.text section

now:

  vmlinux.o: warning: objtool: __flush_tlb_all_noinstr+0x4: call to pv_ops[1]() leaves .noinstr.text section

Signed-off-by: Valentin Schneider <vschneid@...hat.com>
---
 tools/objtool/check.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 6604f5d038aad..5f1d0f95fc04b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3448,7 +3448,7 @@ static inline bool func_uaccess_safe(struct symbol *func)
 	return false;
 }
 
-static inline const char *call_dest_name(struct instruction *insn)
+static inline const char *call_dest_name(struct objtool_file *file, struct instruction *insn)
 {
 	static char pvname[19];
 	struct reloc *reloc;
@@ -3457,9 +3457,9 @@ static inline const char *call_dest_name(struct instruction *insn)
 	if (insn_call_dest(insn))
 		return insn_call_dest(insn)->name;
 
-	reloc = insn_reloc(NULL, insn);
+	reloc = insn_reloc(file, insn);
 	if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
-		idx = (reloc_addend(reloc) / sizeof(void *));
+		idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
 		snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
 		return pvname;
 	}
@@ -3538,17 +3538,20 @@ static int validate_call(struct objtool_file *file,
 {
 	if (state->noinstr && state->instr <= 0 &&
 	    !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
-		WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
+		WARN_INSN(insn, "call to %s() leaves .noinstr.text section",
+			  call_dest_name(file, insn));
 		return 1;
 	}
 
 	if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
-		WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
+		WARN_INSN(insn, "call to %s() with UACCESS enabled",
+			  call_dest_name(file, insn));
 		return 1;
 	}
 
 	if (state->df) {
-		WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
+		WARN_INSN(insn, "call to %s() with DF set",
+			  call_dest_name(file, insn));
 		return 1;
 	}
 
-- 
2.43.0