x86/unwind/orc: Change REG_SP_INDIRECT

Currently REG_SP_INDIRECT is unused but means (%rsp + offset),
change it to mean (%rsp) + offset.

The reason is that we're going to swizzle stack in the middle of a C
function with non-trivial stack footprint. This means that when the
unwinder finds the ToS, it needs to dereference it (%rsp) and then add
the offset to the next frame, resulting in: (%rsp) + offset

This is somewhat unfortunate, since REG_BP_INDIRECT is used (by DRAP)
and thus needs to retain the current (%rbp + offset).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 73f8001..2a1d47f 100644 (file)
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -471,7 +471,7 @@ bool unwind_next_frame(struct unwind_state *state)
                break;
 
        case ORC_REG_SP_INDIRECT:
-               sp = state->sp + orc->sp_offset;
+               sp = state->sp;
                indirect = true;
                break;
 
@@ -521,6 +521,9 @@ bool unwind_next_frame(struct unwind_state *state)
        if (indirect) {
                if (!deref_stack_reg(state, sp, &sp))
                        goto err;
+
+               if (orc->sp_reg == ORC_REG_SP_INDIRECT)
+                       sp += orc->sp_offset;
        }
 
        /* Find IP, SP and possibly regs: */

diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index c53fae9..f5a8508 100644 (file)
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -55,7 +55,7 @@ static void print_reg(unsigned int reg, int offset)
        if (reg == ORC_REG_BP_INDIRECT)
                printf("(bp%+d)", offset);
        else if (reg == ORC_REG_SP_INDIRECT)
-               printf("(sp%+d)", offset);
+               printf("(sp)%+d", offset);
        else if (reg == ORC_REG_UNDEFINED)
                printf("(und)");
        else