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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>
This commit is contained in:
Peter Zijlstra 2021-02-03 12:02:21 +01:00
parent 9077c016a3
commit 87ccc826bf
2 changed files with 5 additions and 2 deletions
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5
arch/x86/kernel/unwind_orc.c
View File

@ -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: */

2
tools/objtool/orc_dump.c
View File

@ -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