On 02/07/2018 05:20 PM, Vineet Gupta wrote:
Didn't do ;)
Is Arnd's patch good to merge or do we need a fixup?
From: Arnd Bergmann <arnd@xxxxxxxx>
Subject: bug.h: work around GCC PR82365 in BUG()
Looking at functions with large stack frames across all architectures led
me discovering that BUG() suffers from the same problem as
fortify_panic(), which I've added a workaround for already. In short,
variables that go out of scope by calling a noreturn function or
__builtin_unreachable() keep using stack space in functions afterwards.
A workaround that was identified is to insert an empty assembler statement
just before calling the function that doesn't return. I'm adding a macro
"barrier_before_unreachable()" to document this, and insert calls to that
in all instances of BUG() that currently suffer from this problem.
..
..
---
arch/arc/include/asm/bug.h | 3 ++-
arch/cris/include/arch-v10/arch/bug.h | 11 +++++++++--
arch/ia64/include/asm/bug.h | 6 +++++-
arch/m68k/include/asm/bug.h | 3 +++
arch/sparc/include/asm/bug.h | 6 +++++-
include/asm-generic/bug.h | 1 +
include/linux/compiler-gcc.h | 15 ++++++++++++++-
include/linux/compiler.h | 5 +++++
8 files changed, 44 insertions(+), 6 deletions(-)
diff -puN arch/arc/include/asm/bug.h~bugh-work-around-gcc-pr82365-in-bug
arch/arc/include/asm/bug.h
--- a/arch/arc/include/asm/bug.h~bugh-work-around-gcc-pr82365-in-bug
+++ a/arch/arc/include/asm/bug.h
@@ -23,7 +23,8 @@ void die(const char *str, struct pt_regs
#define BUG() do { \
pr_warn("BUG: failure at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \
- dump_stack(); \
+ barrier_before_unreachable(); \
+ __builtin_trap(); \
} while (0)
For ARC, it is double win.
1. Fixes 3 -Wreturn-type warnings
| ../net/core/ethtool.c:311:1: warning: control reaches end of non-void function
[-Wreturn-type]
| ../kernel/sched/core.c:3246:1: warning: control reaches end of non-void
function [-Wreturn-type]
| ../include/linux/sunrpc/svc_xprt.h:180:1: warning: control reaches end of
non-void function [-Wreturn-type]
2. bloat-o-meter reports code size improvements as gcc elides the generated code
for stack return.
Acked-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> # for arch/arc
Tested-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> # for arch/arc
Ping ?
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