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Message-ID: <a7d6d0c20deaccfcbc74c3149e782538461fd6fe.1689091394.git.christophe.leroy@csgroup.eu>
Date: Tue, 11 Jul 2023 18:08:27 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Sathvika Vasireddy <sv@...ux.ibm.com>,
Naveen N Rao <naveen@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v4 01/15] Revert "powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with asm goto"
This reverts commit 1e688dd2a3d6759d416616ff07afc4bb836c4213.
That commit aimed at optimising the code around generation of
WARN_ON/BUG_ON but this leads to a lot of dead code erroneously
generated by GCC.
That dead code becomes a problem when we start using objtool validation
because objtool will abort validation with a warning as soon as it
detects unreachable code. This is because unreachable code might
be the indication that objtool doesn't properly decode object text.
text data bss dec hex filename
9551585 3627834 224376 13403795 cc8693 vmlinux.before
9535281 3628358 224376 13388015 cc48ef vmlinux.after
Once this change is reverted, in a standard configuration (pmac32 +
function tracer) the text is reduced by 16k which is around 1.7%
We already had problem with it when starting to use objtool on powerpc
as a replacement for recordmcount, see commit 93e3f45a2631 ("powerpc:
Fix __WARN_FLAGS() for use with Objtool")
There is also a problem with at least GCC 12, on ppc64_defconfig +
CONFIG_CC_OPTIMIZE_FOR_SIZE=y + CONFIG_DEBUG_SECTION_MISMATCH=y :
LD .tmp_vmlinux.kallsyms1
powerpc64-linux-ld: net/ipv4/tcp_input.o:(__ex_table+0xc4): undefined reference to `.L2136'
make[2]: *** [scripts/Makefile.vmlinux:36: vmlinux] Error 1
make[1]: *** [/home/chleroy/linux-powerpc/Makefile:1238: vmlinux] Error 2
Taking into account that other problems are encountered with that
'asm goto' in WARN_ON(), including build failures, keeping that
change is not worth it allthough it is primarily a compiler bug.
Revert it for now.
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Acked-by: Naveen N Rao <naveen@...nel.org>
---
arch/powerpc/include/asm/book3s/64/kup.h | 2 +-
arch/powerpc/include/asm/bug.h | 67 ++++--------------------
arch/powerpc/kernel/misc_32.S | 2 +-
arch/powerpc/kernel/traps.c | 9 +---
4 files changed, 15 insertions(+), 65 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h
index 497a7bd31ecc..e875cb7e68dc 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h
@@ -90,7 +90,7 @@
/* Prevent access to userspace using any key values */
LOAD_REG_IMMEDIATE(\gpr2, AMR_KUAP_BLOCKED)
999: tdne \gpr1, \gpr2
- EMIT_WARN_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE)
+ EMIT_BUG_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE)
END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 67)
#endif
.endm
diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 492530adecc2..abb608dff15a 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -4,14 +4,13 @@
#ifdef __KERNEL__
#include <asm/asm-compat.h>
-#include <asm/extable.h>
#ifdef CONFIG_BUG
#ifdef __ASSEMBLY__
#include <asm/asm-offsets.h>
#ifdef CONFIG_DEBUG_BUGVERBOSE
-.macro __EMIT_BUG_ENTRY addr,file,line,flags
+.macro EMIT_BUG_ENTRY addr,file,line,flags
.section __bug_table,"aw"
5001: .4byte \addr - .
.4byte 5002f - .
@@ -23,7 +22,7 @@
.previous
.endm
#else
-.macro __EMIT_BUG_ENTRY addr,file,line,flags
+.macro EMIT_BUG_ENTRY addr,file,line,flags
.section __bug_table,"aw"
5001: .4byte \addr - .
.short \flags
@@ -32,18 +31,6 @@
.endm
#endif /* verbose */
-.macro EMIT_WARN_ENTRY addr,file,line,flags
- EX_TABLE(\addr,\addr+4)
- __EMIT_BUG_ENTRY \addr,\file,\line,\flags
-.endm
-
-.macro EMIT_BUG_ENTRY addr,file,line,flags
- .if \flags & 1 /* BUGFLAG_WARNING */
- .err /* Use EMIT_WARN_ENTRY for warnings */
- .endif
- __EMIT_BUG_ENTRY \addr,\file,\line,\flags
-.endm
-
#else /* !__ASSEMBLY__ */
/* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and
sizeof(struct bug_entry), respectively */
@@ -73,16 +60,6 @@
"i" (sizeof(struct bug_entry)), \
##__VA_ARGS__)
-#define WARN_ENTRY(insn, flags, label, ...) \
- asm_volatile_goto( \
- "1: " insn "\n" \
- EX_TABLE(1b, %l[label]) \
- _EMIT_BUG_ENTRY \
- : : "i" (__FILE__), "i" (__LINE__), \
- "i" (flags), \
- "i" (sizeof(struct bug_entry)), \
- ##__VA_ARGS__ : : label)
-
/*
* BUG_ON() and WARN_ON() do their best to cooperate with compile-time
* optimisations. However depending on the complexity of the condition
@@ -95,16 +72,7 @@
} while (0)
#define HAVE_ARCH_BUG
-#define __WARN_FLAGS(flags) do { \
- __label__ __label_warn_on; \
- \
- WARN_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags), __label_warn_on); \
- barrier_before_unreachable(); \
- __builtin_unreachable(); \
- \
-__label_warn_on: \
- break; \
-} while (0)
+#define __WARN_FLAGS(flags) BUG_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags))
#ifdef CONFIG_PPC64
#define BUG_ON(x) do { \
@@ -117,25 +85,15 @@ __label_warn_on: \
} while (0)
#define WARN_ON(x) ({ \
- bool __ret_warn_on = false; \
- do { \
- if (__builtin_constant_p((x))) { \
- if (!(x)) \
- break; \
+ int __ret_warn_on = !!(x); \
+ if (__builtin_constant_p(__ret_warn_on)) { \
+ if (__ret_warn_on) \
__WARN(); \
- __ret_warn_on = true; \
- } else { \
- __label__ __label_warn_on; \
- \
- WARN_ENTRY(PPC_TLNEI " %4, 0", \
- BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN), \
- __label_warn_on, \
- "r" ((__force long)(x))); \
- break; \
-__label_warn_on: \
- __ret_warn_on = true; \
- } \
- } while (0); \
+ } else { \
+ BUG_ENTRY(PPC_TLNEI " %4, 0", \
+ BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN), \
+ "r" (__ret_warn_on)); \
+ } \
unlikely(__ret_warn_on); \
})
@@ -148,11 +106,8 @@ __label_warn_on: \
#ifdef __ASSEMBLY__
.macro EMIT_BUG_ENTRY addr,file,line,flags
.endm
-.macro EMIT_WARN_ENTRY addr,file,line,flags
-.endm
#else /* !__ASSEMBLY__ */
#define _EMIT_BUG_ENTRY
-#define _EMIT_WARN_ENTRY
#endif
#endif /* CONFIG_BUG */
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index daf8f87d2372..fd11ec42df89 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -237,7 +237,7 @@ _GLOBAL(copy_page)
addi r3,r3,-4
0: twnei r5, 0 /* WARN if r3 is not cache aligned */
- EMIT_WARN_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING
+ EMIT_BUG_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING
addi r4,r4,-4
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index ab95105c69ca..f5ce282dc4b8 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1508,13 +1508,8 @@ static void do_program_check(struct pt_regs *regs)
if (!(regs->msr & MSR_PR) && /* not user-mode */
report_bug(bugaddr, regs) == BUG_TRAP_TYPE_WARN) {
- const struct exception_table_entry *entry;
-
- entry = search_exception_tables(bugaddr);
- if (entry) {
- regs_set_return_ip(regs, extable_fixup(entry) + regs->nip - bugaddr);
- return;
- }
+ regs_add_return_ip(regs, 4);
+ return;
}
if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE) && user_mode(regs)) {
--
2.41.0
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