lkml.org 
[lkml]   [2021]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH v2 1/3] 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>
---
arch/x86/kernel/unwind_orc.c | 5 ++++-
tools/objtool/orc_dump.c | 2 +-
2 files changed, 5 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -471,7 +471,7 @@ bool unwind_next_frame(struct unwind_sta
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_sta
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: */
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -54,7 +54,7 @@ static void print_reg(unsigned int reg,
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

\
 
 \ /
  Last update: 2021-02-09 10:42    [W:0.097 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site