From: Borislav Petkov <bp@alien8.de>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Richard Biener <rguenther@suse.de>, Michael Matz <matz@suse.de>,
gcc@gcc.gnu.org, Nadav Amit <namit@vmware.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Sam Ravnborg <sam@ravnborg.org>,
Alok Kataria <akataria@vmware.com>,
Christopher Li <sparse@chrisli.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"H. Peter Anvin" <hpa@zytor.com>, Jan Beulich <JBeulich@suse.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Juergen Gross <jgross@suse.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
Kees Cook <keescook@chromium.org>,
linux-sparse@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Philippe Ombredanne <pombredanne@nexb.com>,
Thomas Gleixner <tglx@linutronix.de>,
virtualization@lists.linux-foundation.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
linux-xtensa@linux-xtensa.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: PROPOSAL: Extend inline asm syntax with size spec
Date: Sat, 13 Oct 2018 21:33:35 +0200 [thread overview]
Message-ID: <20181013193335.GD31650@zn.tnic> (raw)
In-Reply-To: <20181010191427.GF5533@zn.tnic>
Ok,
with Segher's help I've been playing with his patch ontop of bleeding
edge gcc 9 and here are my observations. Please double-check me for
booboos so that they can be addressed while there's time.
So here's what I see ontop of 4.19-rc7:
First marked the alternative asm() as inline and undeffed the "inline"
keyword. I need to do that because of the funky games we do with
"inline" redefinitions in include/linux/compiler_types.h.
And Segher hinted at either doing:
asm volatile inline(...
or
asm volatile __inline__(...
but both "inline" variants are defined as macros in that file.
Which means we either need to #undef inline before using it in asm() or
come up with something cleverer.
Anyway, did this:
---
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 4cd6a3b71824..7c0639087da7 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -165,11 +165,13 @@ static inline int alternatives_text_reserved(void *start, void *end)
* For non barrier like inlines please define new variants
* without volatile and memory clobber.
*/
+
+#undef inline
#define alternative(oldinstr, newinstr, feature) \
- asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
+ asm volatile inline(ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
- asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
+ asm volatile inline(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
/*
* Alternative inline assembly with input.
---
Build failed at link time with:
arch/x86/boot/compressed/cmdline.o: In function `native_save_fl':
cmdline.c:(.text+0x0): multiple definition of `native_save_fl'
arch/x86/boot/compressed/misc.o:misc.c:(.text+0x1e0): first defined here
arch/x86/boot/compressed/cmdline.o: In function `native_restore_fl':
cmdline.c:(.text+0x10): multiple definition of `native_restore_fl'
arch/x86/boot/compressed/misc.o:misc.c:(.text+0x1f0): first defined here
arch/x86/boot/compressed/error.o: In function `native_save_fl':
error.c:(.text+0x0): multiple definition of `native_save_fl'
which I had to fix with this:
---
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index 15450a675031..0d772598c37c 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -14,8 +14,7 @@
*/
/* Declaration required for gcc < 4.9 to prevent -Werror=missing-prototypes */
-extern inline unsigned long native_save_fl(void);
-extern inline unsigned long native_save_fl(void)
+static inline unsigned long native_save_fl(void)
{
unsigned long flags;
@@ -33,8 +32,7 @@ ex
---
That "extern inline" declaration looks fishy to me anyway, maybe not really
needed ? Apparently, gcc < 4.9 complains with -Werror=missing-prototypes...
Then the build worked and the results look like this:
text data bss dec hex filename
17287384 5040656 2019532 24347572 17383b4 vmlinux-before
17288020 5040656 2015436 24344112 1737630 vmlinux-2nd-version
so some inlining must be happening.
Then I did this:
---
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index 9c5606d88f61..a0170344cf08 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -20,7 +20,7 @@ unsigned long __clear_user(void __user *addr, unsigned long size)
/* no memory constraint because it doesn't change any memory gcc knows
about */
stac();
- asm volatile(
+ asm volatile inline(
" testq %[size8],%[size8]\n"
" jz 4f\n"
"0: movq $0,(%[dst])\n"
---
to force inlining of a somewhat bigger asm() statement. And yap, more
got inlined:
text data bss dec hex filename
17287384 5040656 2019532 24347572 17383b4 vmlinux-before
17288020 5040656 2015436 24344112 1737630 vmlinux-2nd-version
17288076 5040656 2015436 24344168 1737668 vmlinux-2nd-version__clear_user
so more stuff gets inlined.
Looking at the asm output, it had before:
---
clear_user:
# ./arch/x86/include/asm/current.h:15: return this_cpu_read_stable(current_task);
#APP
# 15 "./arch/x86/include/asm/current.h" 1
movq %gs:current_task,%rax #, pfo_ret__
# 0 "" 2
# arch/x86/lib/usercopy_64.c:51: if (access_ok(VERIFY_WRITE, to, n))
#NO_APP
movq 2520(%rax), %rdx # pfo_ret___12->thread.addr_limit.seg, _1
movq %rdi, %rax # to, tmp93
addq %rsi, %rax # n, tmp93
jc .L3 #,
# arch/x86/lib/usercopy_64.c:51: if (access_ok(VERIFY_WRITE, to, n))
cmpq %rax, %rdx # tmp93, _1
jb .L3 #,
# arch/x86/lib/usercopy_64.c:52: return __clear_user(to, n);
jmp __clear_user #
---
note the JMP to __clear_user. After marking the asm() in __clear_user() as
inline, clear_user() inlines __clear_user() directly:
---
clear_user:
# ./arch/x86/include/asm/current.h:15: return this_cpu_read_stable(current_task);
#APP
# 15 "./arch/x86/include/asm/current.h" 1
movq %gs:current_task,%rax #, pfo_ret__
# 0 "" 2
# arch/x86/lib/usercopy_64.c:51: if (access_ok(VERIFY_WRITE, to, n))
#NO_APP
movq 2520(%rax), %rdx # pfo_ret___12->thread.addr_limit.seg, _1
movq %rdi, %rax # to, tmp95
addq %rsi, %rax # n, tmp95
jc .L8 #,
# arch/x86/lib/usercopy_64.c:51: if (access_ok(VERIFY_WRITE, to, n))
cmpq %rax, %rdx # tmp95, _1
jb .L8 #,
# ./arch/x86/include/asm/smap.h:58: alternative("", __stringify(__ASM_STAC), X86_FEATURE_SMAP);
...
this last line is the stac() macro which gets inlined due to the
alternative() inlined macro above.
So I guess this all looks like what we wanted.
And if this lands in gcc9, we would need to do a asm_volatile() macro
which is defined differently based on the compiler used.
Thoughts, suggestions, etc are most welcome.
Thx.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2018-10-13 19:33 UTC|newest]
Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-03 21:30 [PATCH v9 00/10] x86: macrofying inline asm Nadav Amit
2018-10-03 21:30 ` [PATCH v9 01/10] xtensa: defining LINKER_SCRIPT for the linker script Nadav Amit
2018-10-04 10:00 ` [tip:x86/build] kbuild/arch/xtensa: Define " tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm Nadav Amit
2018-10-04 10:01 ` [tip:x86/build] kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs tip-bot for Nadav Amit
2018-11-06 18:57 ` [PATCH v9 02/10] Makefile: Prepare for using macros for inline asm Logan Gunthorpe
2018-11-06 19:18 ` Nadav Amit
2018-11-06 20:01 ` Logan Gunthorpe
2018-11-07 18:01 ` Nadav Amit
2018-11-07 18:53 ` Logan Gunthorpe
2018-11-07 18:56 ` Nadav Amit
2018-11-07 21:43 ` Logan Gunthorpe
2018-11-07 21:50 ` hpa
2018-11-08 6:18 ` Nadav Amit
2018-11-08 17:14 ` Logan Gunthorpe
2018-11-08 19:54 ` Nadav Amit
2018-11-08 20:00 ` Logan Gunthorpe
2018-11-08 20:18 ` Nadav Amit
2018-11-10 22:04 ` Nadav Amit
2018-11-13 4:56 ` Logan Gunthorpe
2018-10-03 21:30 ` [PATCH v9 03/10] x86: objtool: use asm macro for better compiler decisions Nadav Amit
2018-10-04 10:02 ` [tip:x86/build] x86/objtool: Use asm macros to work around GCC inlining bugs tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 04/10] x86: refcount: prevent gcc distortions Nadav Amit
2018-10-04 7:57 ` Ingo Molnar
2018-10-04 8:33 ` Ingo Molnar
2018-10-04 8:40 ` hpa
2018-10-04 8:56 ` Ingo Molnar
2018-10-04 8:56 ` Nadav Amit
2018-10-04 9:02 ` hpa
2018-10-04 9:16 ` Ingo Molnar
2018-10-04 19:33 ` H. Peter Anvin
2018-10-04 20:05 ` Nadav Amit
2018-10-04 20:08 ` H. Peter Anvin
2018-10-04 20:29 ` Andy Lutomirski
2018-10-04 23:11 ` H. Peter Anvin
2018-10-06 1:40 ` Rasmus Villemoes
2018-10-04 9:12 ` Ingo Molnar
2018-10-04 9:17 ` hpa
2018-10-04 9:30 ` Nadav Amit
2018-10-04 9:45 ` Ingo Molnar
2018-10-04 10:23 ` Nadav Amit
2018-10-05 9:31 ` Ingo Molnar
2018-10-05 11:20 ` Borislav Petkov
2018-10-05 12:52 ` Ingo Molnar
2018-10-05 20:27 ` [PATCH 0/3] Macrofying inline asm rebased Nadav Amit
2018-10-05 20:27 ` [PATCH 1/3] x86/extable: Macrofy inline assembly code to work around GCC inlining bugs Nadav Amit
2018-10-06 14:42 ` [tip:x86/build] " tip-bot for Nadav Amit
2018-10-05 20:27 ` [PATCH 2/3] x86/cpufeature: " Nadav Amit
2018-10-06 14:43 ` [tip:x86/build] " tip-bot for Nadav Amit
2018-10-05 20:27 ` [PATCH 3/3] x86/jump-labels: " Nadav Amit
2018-10-06 14:44 ` [tip:x86/build] " tip-bot for Nadav Amit
2018-10-08 2:17 ` [PATCH v9 04/10] x86: refcount: prevent gcc distortions Nadav Amit
2018-10-04 8:40 ` Nadav Amit
2018-10-04 9:01 ` Ingo Molnar
2018-10-04 10:02 ` [tip:x86/build] x86/refcount: Work around GCC inlining bug tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 05/10] x86: alternatives: macrofy locks for better inlining Nadav Amit
2018-10-04 10:03 ` [tip:x86/build] x86/alternatives: Macrofy lock prefixes to work around GCC inlining bugs tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 06/10] x86: bug: prevent gcc distortions Nadav Amit
2018-10-04 10:03 ` [tip:x86/build] x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 07/10] x86: prevent inline distortion by paravirt ops Nadav Amit
2018-10-04 10:04 ` [tip:x86/build] x86/paravirt: Work around GCC inlining bugs when compiling " tip-bot for Nadav Amit
2018-10-03 21:30 ` [PATCH v9 08/10] x86: extable: use macros instead of inline assembly Nadav Amit
2018-10-03 21:30 ` [PATCH v9 09/10] x86: cpufeature: " Nadav Amit
2018-10-03 21:31 ` [PATCH v9 10/10] x86: jump-labels: " Nadav Amit
2018-10-07 9:18 ` PROPOSAL: Extend inline asm syntax with size spec Borislav Petkov
[not found] ` <20181007132228.GJ29268@gate.crashing.org>
2018-10-07 14:13 ` Borislav Petkov
2018-10-07 15:14 ` Segher Boessenkool
2018-10-08 5:58 ` Ingo Molnar
2018-10-08 7:53 ` Segher Boessenkool
2018-10-07 15:53 ` Michael Matz
2018-10-08 6:13 ` Ingo Molnar
2018-10-08 8:18 ` Segher Boessenkool
2018-10-08 7:31 ` Segher Boessenkool
2018-10-08 9:07 ` Richard Biener
2018-10-08 10:02 ` Segher Boessenkool
2018-10-09 14:53 ` Segher Boessenkool
2018-10-10 6:35 ` Ingo Molnar
2018-10-10 7:12 ` Richard Biener
2018-10-10 7:22 ` Ingo Molnar
2018-10-10 8:03 ` Segher Boessenkool
2018-10-10 8:19 ` Borislav Petkov
2018-10-10 8:35 ` Richard Biener
2018-10-10 18:54 ` Segher Boessenkool
2018-10-10 19:14 ` Borislav Petkov
2018-10-13 19:33 ` Borislav Petkov [this message]
2018-10-13 21:14 ` Alexander Monakov
2018-10-13 21:30 ` Borislav Petkov
2018-10-25 10:24 ` Borislav Petkov
2018-10-31 12:55 ` Peter Zijlstra
2018-10-31 13:11 ` Peter Zijlstra
2018-10-31 16:31 ` Segher Boessenkool
2018-11-01 5:20 ` Joe Perches
2018-11-01 9:01 ` Peter Zijlstra
2018-11-01 9:20 ` Joe Perches
2018-11-01 11:15 ` Peter Zijlstra
2018-12-27 4:47 ` Masahiro Yamada
2018-10-10 10:29 ` Richard Biener
2018-10-10 7:53 ` Segher Boessenkool
2018-10-10 16:31 ` Nadav Amit
2018-10-10 19:21 ` Segher Boessenkool
2018-10-11 7:04 ` Richard Biener
2018-11-29 11:46 ` Masahiro Yamada
2018-11-29 12:25 ` Segher Boessenkool
2018-11-30 9:06 ` Boris Petkov
2018-11-30 13:16 ` Segher Boessenkool
2018-12-10 8:16 ` Masahiro Yamada
2018-11-29 13:07 ` Borislav Petkov
2018-11-29 13:09 ` Richard Biener
2018-11-29 13:16 ` Borislav Petkov
2018-11-29 13:24 ` Richard Biener
2018-10-08 16:24 ` David Laight
2018-10-07 16:09 ` Nadav Amit
2018-10-07 16:46 ` Richard Biener
2018-10-07 19:06 ` Nadav Amit
2018-10-07 19:52 ` Jeff Law
2018-10-08 7:46 ` Richard Biener
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