[arch-commits] Commit in linux-lts/trunk (4 files)

Jan Steffens heftig at archlinux.org
Sat May 9 19:59:23 UTC 2020


    Date: Saturday, May 9, 2020 @ 19:59:23
  Author: heftig
Revision: 382974

5.4.39-3: more GCC 10 fixes

Added:
  linux-lts/trunk/0002-Makefile-disallow-data-races-on-gcc-10-as-well.patch
  linux-lts/trunk/0003-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch
Modified:
  linux-lts/trunk/0001-gcc-common.h-Update-for-GCC-10.patch
  linux-lts/trunk/PKGBUILD

-----------------------------------------------------------+
 0001-gcc-common.h-Update-for-GCC-10.patch                 |    2 
 0002-Makefile-disallow-data-races-on-gcc-10-as-well.patch |   32 ++
 0003-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch    |  131 ++++++++++++
 PKGBUILD                                                  |    8 
 4 files changed, 170 insertions(+), 3 deletions(-)

Modified: 0001-gcc-common.h-Update-for-GCC-10.patch
===================================================================
--- 0001-gcc-common.h-Update-for-GCC-10.patch	2020-05-09 19:59:19 UTC (rev 382973)
+++ 0001-gcc-common.h-Update-for-GCC-10.patch	2020-05-09 19:59:23 UTC (rev 382974)
@@ -2,7 +2,7 @@
 From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Pierret=20=28fepitre=29?=
  <frederic.pierret at qubes-os.org>
 Date: Tue, 7 Apr 2020 13:32:59 +0200
-Subject: [PATCH] gcc-common.h: Update for GCC 10
+Subject: [PATCH 1/3] gcc-common.h: Update for GCC 10
 MIME-Version: 1.0
 Content-Type: text/plain; charset=UTF-8
 Content-Transfer-Encoding: 8bit

Added: 0002-Makefile-disallow-data-races-on-gcc-10-as-well.patch
===================================================================
--- 0002-Makefile-disallow-data-races-on-gcc-10-as-well.patch	                        (rev 0)
+++ 0002-Makefile-disallow-data-races-on-gcc-10-as-well.patch	2020-05-09 19:59:23 UTC (rev 382974)
@@ -0,0 +1,32 @@
+From 6a183a41a1945cb79660a78536182ce9c2568291 Mon Sep 17 00:00:00 2001
+From: Sergei Trofimovich <slyfox at gentoo.org>
+Date: Tue, 17 Mar 2020 00:07:18 +0000
+Subject: [PATCH 2/3] Makefile: disallow data races on gcc-10 as well
+
+gcc-10 will rename --param=allow-store-data-races=0
+to -fno-allow-store-data-races.
+
+The flag change happened at https://gcc.gnu.org/PR92046.
+
+Signed-off-by: Sergei Trofimovich <slyfox at gentoo.org>
+Acked-by: Jiri Kosina <jkosina at suse.cz>
+Signed-off-by: Masahiro Yamada <masahiroy at kernel.org>
+---
+ Makefile | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/Makefile b/Makefile
+index ff2b90ddc9bc..c8dc1357079b 100644
+--- a/Makefile
++++ b/Makefile
+@@ -713,6 +713,7 @@ endif
+ 
+ # Tell gcc to never replace conditional load with a non-conditional one
+ KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
++KBUILD_CFLAGS	+= $(call cc-option,-fno-allow-store-data-races)
+ 
+ include scripts/Makefile.kcov
+ include scripts/Makefile.gcc-plugins
+-- 
+2.26.2
+

Added: 0003-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch
===================================================================
--- 0003-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch	                        (rev 0)
+++ 0003-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch	2020-05-09 19:59:23 UTC (rev 382974)
@@ -0,0 +1,131 @@
+From 2f18ace75890ccd9681f210efdb58662db0cb4c4 Mon Sep 17 00:00:00 2001
+From: Borislav Petkov <bp at suse.de>
+Date: Wed, 22 Apr 2020 18:11:30 +0200
+Subject: [PATCH 3/3] x86: Fix early boot crash on gcc-10, next try
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+... or the odyssey of trying to disable the stack protector for the
+function which generates the stack canary value.
+
+The whole story started with Sergei reporting a boot crash with a kernel
+built with gcc-10:
+
+  Kernel panic — not syncing: stack-protector: Kernel stack is corrupted in: start_secondary
+  CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.6.0-rc5—00235—gfffb08b37df9 #139
+  Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./H77M—D3H, BIOS F12 11/14/2013
+  Call Trace:
+    dump_stack
+    panic
+    ? start_secondary
+    __stack_chk_fail
+    start_secondary
+    secondary_startup_64
+  -—-[ end Kernel panic — not syncing: stack—protector: Kernel stack is corrupted in: start_secondary
+
+This happens because gcc-10 tail-call optimizes the last function call
+in start_secondary() - cpu_startup_entry() - and thus emits a stack
+canary check which fails because the canary value changes after the
+boot_init_stack_canary() call.
+
+To fix that, the initial attempt was to mark the one function which
+generates the stack canary with:
+
+  __attribute__((optimize("-fno-stack-protector"))) ... start_secondary(void *unused)
+
+however, using the optimize attribute doesn't work cumulatively
+as the attribute does not add to but rather replaces previously
+supplied optimization options - roughly all -fxxx options.
+
+The key one among them being -fno-omit-frame-pointer and thus leading to
+not present frame pointer - frame pointer which the kernel needs.
+
+The next attempt to prevent compilers from tail-call optimizing
+the last function call cpu_startup_entry(), shy of carving out
+start_secondary() into a separate compilation unit and building it with
+-fno-stack-protector, is this one.
+
+The current solution is short and sweet, and reportedly, is supported by
+both compilers so let's see how far we'll get this time.
+
+Reported-by: Sergei Trofimovich <slyfox at gentoo.org>
+Signed-off-by: Borislav Petkov <bp at suse.de>
+Reviewed-by: Nick Desaulniers <ndesaulniers at google.com>
+Reviewed-by: Kees Cook <keescook at chromium.org>
+Link: https://lkml.kernel.org/r/20200314164451.346497-1-slyfox@gentoo.org
+---
+ arch/x86/include/asm/stackprotector.h | 7 ++++++-
+ arch/x86/kernel/smpboot.c             | 8 ++++++++
+ arch/x86/xen/smp_pv.c                 | 1 +
+ include/linux/compiler.h              | 6 ++++++
+ 4 files changed, 21 insertions(+), 1 deletion(-)
+
+diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
+index 91e29b6a86a5..9804a7957f4e 100644
+--- a/arch/x86/include/asm/stackprotector.h
++++ b/arch/x86/include/asm/stackprotector.h
+@@ -55,8 +55,13 @@
+ /*
+  * Initialize the stackprotector canary value.
+  *
+- * NOTE: this must only be called from functions that never return,
++ * NOTE: this must only be called from functions that never return
+  * and it must always be inlined.
++ *
++ * In addition, it should be called from a compilation unit for which
++ * stack protector is disabled. Alternatively, the caller should not end
++ * with a function call which gets tail-call optimized as that would
++ * lead to checking a modified canary value.
+  */
+ static __always_inline void boot_init_stack_canary(void)
+ {
+diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
+index 69881b2d446c..9674321ce3a3 100644
+--- a/arch/x86/kernel/smpboot.c
++++ b/arch/x86/kernel/smpboot.c
+@@ -262,6 +262,14 @@ static void notrace start_secondary(void *unused)
+ 
+ 	wmb();
+ 	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
++
++	/*
++	 * Prevent tail call to cpu_startup_entry() because the stack protector
++	 * guard has been changed a couple of function calls up, in
++	 * boot_init_stack_canary() and must not be checked before tail calling
++	 * another function.
++	 */
++	prevent_tail_call_optimization();
+ }
+ 
+ /**
+diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
+index 802ee5bba66c..0cebe5db691d 100644
+--- a/arch/x86/xen/smp_pv.c
++++ b/arch/x86/xen/smp_pv.c
+@@ -92,6 +92,7 @@ asmlinkage __visible void cpu_bringup_and_idle(void)
+ 	cpu_bringup();
+ 	boot_init_stack_canary();
+ 	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
++	prevent_tail_call_optimization();
+ }
+ 
+ void xen_smp_intr_free_pv(unsigned int cpu)
+diff --git a/include/linux/compiler.h b/include/linux/compiler.h
+index 034b0a644efc..732754d96039 100644
+--- a/include/linux/compiler.h
++++ b/include/linux/compiler.h
+@@ -356,4 +356,10 @@ static inline void *offset_to_ptr(const int *off)
+ /* &a[0] degrades to a pointer: a different type from an array */
+ #define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
+ 
++/*
++ * This is needed in functions which generate the stack canary, see
++ * arch/x86/kernel/smpboot.c::start_secondary() for an example.
++ */
++#define prevent_tail_call_optimization()	asm("")
++
+ #endif /* __LINUX_COMPILER_H */
+-- 
+2.26.2
+

Modified: PKGBUILD
===================================================================
--- PKGBUILD	2020-05-09 19:59:19 UTC (rev 382973)
+++ PKGBUILD	2020-05-09 19:59:23 UTC (rev 382974)
@@ -2,7 +2,7 @@
 
 pkgbase=linux-lts
 pkgver=5.4.39
-pkgrel=2
+pkgrel=3
 pkgdesc='LTS Linux'
 url="https://www.kernel.org/"
 arch=(x86_64)
@@ -18,6 +18,8 @@
   config         # the main kernel config file
   0001-add-sysctl-and-CONFIG-for-unprivileged_userns_clone.patch
   0001-gcc-common.h-Update-for-GCC-10.patch
+  0002-Makefile-disallow-data-races-on-gcc-10-as-well.patch
+  0003-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch
   sphinx-workaround.patch
 )
 validpgpkeys=(
@@ -29,7 +31,9 @@
             'SKIP'
             '8b202067f6f0adbe2f8d4290624005f4fa1fff32aaa42f979c9ab03f6b74b62f'
             'a13581d3c6dc595206e4fe7fcf6b542e7a1bdbe96101f0f010fc5be49f99baf2'
-            '5ccd721fea425fc9b1c08edf4f8ea94ee5737c193009b7a4253f7a383b273858'
+            '2b63997760aa823b5907c3c5653f35265e9c6320b812b4f4a8e7c74256dab7c7'
+            '875400c2dded3c05588025e0095b529c53f317abcccc99507eff0a75f24aa93f'
+            'b7505c345722c4c1ca27c8d99114d4b8746e530acd9b7c4e5a0601b89bfba2d2'
             'b7c814c8183e4645947a6dcc3cbf80431de8a8fd4e895b780f9a5fd92f82cb8e')
 
 export KBUILD_BUILD_HOST=archlinux


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