linux-kernel - [RFC v5 17/57] objtool: Make stack validation more generic

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Date:   Thu,  9 Jan 2020 16:02:20 +0000
From:   Julien Thierry <jthierry@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     jpoimboe@...hat.com, peterz@...radead.org, raphael.gault@....com,
        catalin.marinas@....com, will@...nel.org,
        Julien Thierry <jthierry@...hat.com>
Subject: [RFC v5 17/57] objtool: Make stack validation more generic

On x86, when calling a function, the new call frame is alway placed at
the start of the stack space this function can freely use. So the frame
pointer is always saved at <function stack start> - 16.

This is not true for the calling convention of all architecture.

When validating the call frame before a call instruction, all that can
be done is check that a frame was created by the current function and
that the frame pointer is correctly pointing to it.

Signed-off-by: Julien Thierry <jthierry@...hat.com>
---
 tools/objtool/check.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0a5c51e4e24c..04434cdbdab6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1176,7 +1176,7 @@ static bool has_modified_stack_frame(struct insn_state *state)
 static bool has_valid_stack_frame(struct insn_state *state)
 {
 	if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
-	    state->regs[CFI_BP].offset == -16)
+	    state->regs[CFI_BP].offset == -state->cfa.offset)
 		return true;
 
 	if (state->drap && state->regs[CFI_BP].base == CFI_BP)
-- 
2.21.0