powerpc: avoid broken GCC attribute((optimize))

PATCH Applied Ard Biesheuvel 5 participants 6 messages Oct 28, 2020 – Nov 25, 2020 PowerPC

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Ard Biesheuvel

author

2020-10-28 08:06 UTC #0 lore raw

PATCH 1/1 powerpc: avoid broken GCC __attribute__((optimize))

Commit 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot") introduced a couple of uses of __attribute__((optimize)) with function scope, to disable the stack protector in some early boot code.

Unfortunately, and this is documented in the GCC man pages [0], overriding function attributes for optimization is broken, and is only supported for debug scenarios, not for production: the problem appears to be that setting GCC -f flags using this method will cause it to forget about some or all other optimization settings that have been applied.

So the only safe way to disable the stack protector is to disable it for the entire source file.

[0] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html

Cc Michael Ellerman <[email protected]>

Cc Benjamin Herrenschmidt <[email protected]>

Cc Paul Mackerras <[email protected]>

Cc Nick Desaulniers <[email protected]>

Cc Arvind Sankar <[email protected]>

Cc Randy Dunlap <[email protected]>

Cc Josh Poimboeuf <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Alexei Starovoitov <[email protected]>

Cc Daniel Borkmann <[email protected]>

Cc Peter Zijlstra (Intel) <[email protected]>

Cc Geert Uytterhoeven <[email protected]>

Cc Kees Cook <[email protected]>

Fixes 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot")

Signed-off-by Ard Biesheuvel <[email protected]>

TL;DR using __attribute__((optimize("-fno-gcse"))) in the BPF interpreter causes the compiler to forget about -fno-asynchronous-unwind-tables passed on the command line, resulting in unexpected .eh_frame sections in vmlinux.

 arch/powerpc/kernel/Makefile   | 3 +++
 arch/powerpc/kernel/paca.c     | 2 +-
 arch/powerpc/kernel/setup.h    | 6 ------
 arch/powerpc/kernel/setup_64.c | 2 +-
 4 files changed, 5 insertions(+), 8 deletions(-)

arch/powerpc/kernel/Makefile +3 -0

index bf0bf1b900d2..fe2ef598e2ea 100644
@@ -173,6 +173,9 @@ KCOV_INSTRUMENT_cputable.o := n
 KCOV_INSTRUMENT_setup_64.o := n
 KCOV_INSTRUMENT_paca.o := n
 
+CFLAGS_setup_64.o		+= -fno-stack-protector
+CFLAGS_paca.o			+= -fno-stack-protector
+
 extra-$(CONFIG_PPC_FPU)		+= fpu.o
 extra-$(CONFIG_ALTIVEC)		+= vector.o
 extra-$(CONFIG_PPC64)		+= entry_64.o

arch/powerpc/kernel/paca.c +1 -1

index 0ad15768d762..fe70834d7283 100644
@@ -208,7 +208,7 @@ static struct rtas_args * __init new_rtas_args(int cpu, unsigned long limit)
 struct paca_struct **paca_ptrs __read_mostly;
 EXPORT_SYMBOL(paca_ptrs);
 
-void __init __nostackprotector initialise_paca(struct paca_struct *new_paca, int cpu)
+void __init initialise_paca(struct paca_struct *new_paca, int cpu)
 {
 #ifdef CONFIG_PPC_PSERIES
 	new_paca->lppaca_ptr = NULL;

arch/powerpc/kernel/setup.h +0 -6

index 2ec835574cc9..2dd0d9cb5a20 100644
@@ -8,12 +8,6 @@
 #ifndef __ARCH_POWERPC_KERNEL_SETUP_H
 #define __ARCH_POWERPC_KERNEL_SETUP_H
 
-#ifdef CONFIG_CC_IS_CLANG
-#define __nostackprotector
-#else
-#define __nostackprotector __attribute__((__optimize__("no-stack-protector")))
-#endif
-
 void initialize_cache_info(void);
 void irqstack_early_init(void);

arch/powerpc/kernel/setup_64.c +1 -1

index bb9cab3641d7..da447a62ea1e 100644
@@ -283,7 +283,7 @@ void __init record_spr_defaults(void)
  * device-tree is not accessible via normal means at this point.
  */
 
-void __init __nostackprotector early_setup(unsigned long dt_ptr)
+void __init early_setup(unsigned long dt_ptr)
 {
 	static __initdata struct paca_struct boot_paca;

Signature · 1 line

2.17.1

Ard Biesheuvel

author

2020-10-28 08:31 UTC #1 lore raw

Quoted 39 lines · Ard Biesheuvel

Commit 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot") introduced a couple of uses of __attribute__((optimize)) with function scope, to disable the stack protector in some early boot code.
Unfortunately, and this is documented in the GCC man pages [0], overriding function attributes for optimization is broken, and is only supported for debug scenarios, not for production: the problem appears to be that setting GCC -f flags using this method will cause it to forget about some or all other optimization settings that have been applied.
So the only safe way to disable the stack protector is to disable it for the entire source file.
[0] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
Cc Michael Ellerman <[email protected]>
Cc Benjamin Herrenschmidt <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Nick Desaulniers <[email protected]>
Cc Arvind Sankar <[email protected]>
Cc Randy Dunlap <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc Alexei Starovoitov <[email protected]>
Cc Daniel Borkmann <[email protected]>
Cc Peter Zijlstra (Intel) <[email protected]>
Cc Geert Uytterhoeven <[email protected]>
Cc Kees Cook <[email protected]>
Fixes 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot")
Signed-off-by Ard Biesheuvel <[email protected]>
---
Related discussion here:
https://lore.kernel.org/lkml/CAMuHMdUg0WJHEcq6to0-eODpXPOywLot6UD2=GFHpzoj_hCoBQ@mail.gmail.com/
TL;DR using __attribute__((optimize("-fno-gcse"))) in the BPF interpreter causes the compiler to forget about -fno-asynchronous-unwind-tables passed on the command line, resulting in unexpected .eh_frame sections in vmlinux.

Quoted 6 lines

 arch/powerpc/kernel/Makefile   | 3 +++
 arch/powerpc/kernel/paca.c     | 2 +-
 arch/powerpc/kernel/setup.h    | 6 ------
 arch/powerpc/kernel/setup_64.c | 2 +-
 4 files changed, 5 insertions(+), 8 deletions(-)

FYI i was notified by one of the robots that I missed one occurrence of __nostackprotector in arch/powerpc/kernel/paca.c

Let me know if I need to resend.

Quoted 60 lines

arch/powerpc/kernel/Makefile +3 -0

index bf0bf1b900d2..fe2ef598e2ea 100644
@@ -173,6 +173,9 @@ KCOV_INSTRUMENT_cputable.o := n
 KCOV_INSTRUMENT_setup_64.o := n
 KCOV_INSTRUMENT_paca.o := n
 
+CFLAGS_setup_64.o              += -fno-stack-protector
+CFLAGS_paca.o                  += -fno-stack-protector
+
 extra-$(CONFIG_PPC_FPU)                += fpu.o
 extra-$(CONFIG_ALTIVEC)                += vector.o
 extra-$(CONFIG_PPC64)          += entry_64.o

arch/powerpc/kernel/paca.c +1 -1

index 0ad15768d762..fe70834d7283 100644
@@ -208,7 +208,7 @@ static struct rtas_args * __init new_rtas_args(int cpu, unsigned long limit)
 struct paca_struct **paca_ptrs __read_mostly;
 EXPORT_SYMBOL(paca_ptrs);
 
-void __init __nostackprotector initialise_paca(struct paca_struct *new_paca, int cpu)
+void __init initialise_paca(struct paca_struct *new_paca, int cpu)
 {
 #ifdef CONFIG_PPC_PSERIES
        new_paca->lppaca_ptr = NULL;

arch/powerpc/kernel/setup.h +0 -6

index 2ec835574cc9..2dd0d9cb5a20 100644
@@ -8,12 +8,6 @@
 #ifndef __ARCH_POWERPC_KERNEL_SETUP_H
 #define __ARCH_POWERPC_KERNEL_SETUP_H
 
-#ifdef CONFIG_CC_IS_CLANG
-#define __nostackprotector
-#else
-#define __nostackprotector __attribute__((__optimize__("no-stack-protector")))
-#endif
-
 void initialize_cache_info(void);
 void irqstack_early_init(void);

arch/powerpc/kernel/setup_64.c +1 -2

index bb9cab3641d7..da447a62ea1e 100644
@@ -283,7 +283,7 @@ void __init record_spr_defaults(void)
  * device-tree is not accessible via normal means at this point.
  */
 
-void __init __nostackprotector early_setup(unsigned long dt_ptr)
+void __init early_setup(unsigned long dt_ptr)
 {
        static __initdata struct paca_struct boot_paca;
 
--

2.17.1

Michael Ellerman

reviewer

2020-10-29 11:37 UTC #2 lore raw

Quoted 40 lines · Ard Biesheuvel

Quoted 39 lines · Ard Biesheuvel
Commit 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot") introduced a couple of uses of __attribute__((optimize)) with function scope, to disable the stack protector in some early boot code.
Unfortunately, and this is documented in the GCC man pages [0], overriding function attributes for optimization is broken, and is only supported for debug scenarios, not for production: the problem appears to be that setting GCC -f flags using this method will cause it to forget about some or all other optimization settings that have been applied.
So the only safe way to disable the stack protector is to disable it for the entire source file.
[0] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html
Cc Michael Ellerman <[email protected]>
Cc Benjamin Herrenschmidt <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Nick Desaulniers <[email protected]>
Cc Arvind Sankar <[email protected]>
Cc Randy Dunlap <[email protected]>
Cc Josh Poimboeuf <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc Alexei Starovoitov <[email protected]>
Cc Daniel Borkmann <[email protected]>
Cc Peter Zijlstra (Intel) <[email protected]>
Cc Geert Uytterhoeven <[email protected]>
Cc Kees Cook <[email protected]>
Fixes 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot")
Signed-off-by Ard Biesheuvel <[email protected]>
---
Related discussion here:
https://lore.kernel.org/lkml/CAMuHMdUg0WJHEcq6to0-eODpXPOywLot6UD2=GFHpzoj_hCoBQ@mail.gmail.com/
TL;DR using __attribute__((optimize("-fno-gcse"))) in the BPF interpreter causes the compiler to forget about -fno-asynchronous-unwind-tables passed on the command line, resulting in unexpected .eh_frame sections in vmlinux.

Quoted 5 lines

 arch/powerpc/kernel/Makefile   | 3 +++
 arch/powerpc/kernel/paca.c     | 2 +-
 arch/powerpc/kernel/setup.h    | 6 ------
 arch/powerpc/kernel/setup_64.c | 2 +-
 4 files changed, 5 insertions(+), 8 deletions(-)

Thanks for the patch.

Quoted 4 lines

FYI i was notified by one of the robots that I missed one occurrence of __nostackprotector in arch/powerpc/kernel/paca.c
Let me know if I need to resend.

That's fine I'll fix it up when applying.

With the existing code, with STACKPROTECTOR_STRONG=y, I see two functions in setup_64.c that are triggering stack protection. One is __init, and the other takes no parameters and is not easily reachable from userspace, so I don't think losing the stack canary on either of those is a concern.

I don't see anything in paca.c triggering stack protection.

I don't think there's any evidence this is causing a bug for us, so I'll plan to put this in next for v5.11.

cheers

kernel test robot

build bot

2020-10-28 10:08 UTC #3 lore raw

In reply to Ard Biesheuvel

I love your patch! Yet something to improve:

Hi Ard,

I love your patch! Yet something to improve:

[auto build test ERROR on powerpc/next]
[also build test ERROR on linus/master linux/master v5.10-rc1 next-20201028] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Ard-Biesheuvel/powerpc-avoid-broken-GCC-__attribute__-optimize/20201028-160558
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc64-randconfig-r003-20201028 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 50dfa19cc799ae7cddd39a95dbfce675a12672ad)

reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross
# install powerpc64 cross compiling tool for clang build
# apt-get install binutils-powerpc64-linux-gnu
# https://github.com/0day-ci/linux/commit/5ccccdce42ea4f2316ac2bf79d5311dc77a70e6e
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Ard-Biesheuvel/powerpc-avoid-broken-GCC-__attribute__-optimize/20201028-160558 git checkout 5ccccdce42ea4f2316ac2bf79d5311dc77a70e6e
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc64

If you fix the issue, kindly add following tag as appropriate

Reported-by kernel test robot <[email protected]>

All errors (new ones prefixed by >>):

>> arch/powerpc/kernel/paca.c:244:6: error: variable has incomplete type 'void'
   void __nostackprotector setup_paca(struct paca_struct *new_paca)
        ^
>> arch/powerpc/kernel/paca.c:244:24: error: expected ';' after top level declarator
   void __nostackprotector setup_paca(struct paca_struct *new_paca)
                          ^
                          ;
>> arch/powerpc/kernel/paca.c:274:2: error: use of undeclared identifier 'paca_nr_cpu_ids'; did you mean 'nr_cpu_ids'?
           paca_nr_cpu_ids = nr_cpu_ids;
           ^~~~~~~~~~~~~~~
           nr_cpu_ids
   include/linux/cpumask.h:39:21: note: 'nr_cpu_ids' declared here
   extern unsigned int nr_cpu_ids;
                       ^
>> arch/powerpc/kernel/paca.c:274:18: error: explicitly assigning value of variable of type 'unsigned int' to itself [-Werror,-Wself-assign]
           paca_nr_cpu_ids = nr_cpu_ids;
           ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~
   arch/powerpc/kernel/paca.c:290:16: error: use of undeclared identifier 'paca_nr_cpu_ids'
           BUG_ON(cpu >= paca_nr_cpu_ids);
                         ^
   arch/powerpc/kernel/paca.c:290:16: error: use of undeclared identifier 'paca_nr_cpu_ids'
   arch/powerpc/kernel/paca.c:290:16: error: use of undeclared identifier 'paca_nr_cpu_ids'
   arch/powerpc/kernel/paca.c:328:2: error: use of undeclared identifier 'paca_nr_cpu_ids'; did you mean 'nr_cpu_ids'?
           paca_nr_cpu_ids = nr_cpu_ids;
           ^~~~~~~~~~~~~~~
           nr_cpu_ids
   include/linux/cpumask.h:39:21: note: 'nr_cpu_ids' declared here
   extern unsigned int nr_cpu_ids;
                       ^
   arch/powerpc/kernel/paca.c:328:18: error: explicitly assigning value of variable of type 'unsigned int' to itself [-Werror,-Wself-assign]
           paca_nr_cpu_ids = nr_cpu_ids;
           ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~
   9 errors generated.
--
>> arch/powerpc/kernel/paca.c:244:6: error: variable has incomplete type 'void'
   void __nostackprotector setup_paca(struct paca_struct *new_paca)
        ^
>> arch/powerpc/kernel/paca.c:244:24: error: expected ';' after top level declarator
   void __nostackprotector setup_paca(struct paca_struct *new_paca)
                          ^
                          ;
>> arch/powerpc/kernel/paca.c:274:2: error: use of undeclared identifier 'paca_nr_cpu_ids'; did you mean 'nr_cpu_ids'?
           paca_nr_cpu_ids = nr_cpu_ids;
           ^~~~~~~~~~~~~~~
           nr_cpu_ids
   include/linux/cpumask.h:39:21: note: 'nr_cpu_ids' declared here
   extern unsigned int nr_cpu_ids;
                       ^
   arch/powerpc/kernel/paca.c:274:18: warning: explicitly assigning value of variable of type 'unsigned int' to itself [-Wself-assign]
           paca_nr_cpu_ids = nr_cpu_ids;
           ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~
   arch/powerpc/kernel/paca.c:290:16: error: use of undeclared identifier 'paca_nr_cpu_ids'
           BUG_ON(cpu >= paca_nr_cpu_ids);
                         ^
   arch/powerpc/kernel/paca.c:290:16: error: use of undeclared identifier 'paca_nr_cpu_ids'
   arch/powerpc/kernel/paca.c:290:16: error: use of undeclared identifier 'paca_nr_cpu_ids'
   arch/powerpc/kernel/paca.c:328:2: error: use of undeclared identifier 'paca_nr_cpu_ids'; did you mean 'nr_cpu_ids'?
           paca_nr_cpu_ids = nr_cpu_ids;
           ^~~~~~~~~~~~~~~
           nr_cpu_ids
   include/linux/cpumask.h:39:21: note: 'nr_cpu_ids' declared here
   extern unsigned int nr_cpu_ids;
                       ^
   arch/powerpc/kernel/paca.c:328:18: warning: explicitly assigning value of variable of type 'unsigned int' to itself [-Wself-assign]
           paca_nr_cpu_ids = nr_cpu_ids;
           ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~

2 warnings and 7 errors generated.

vim +/void +244 arch/powerpc/kernel/paca.c

1426d5a3bd07589 Michael Ellerman       2010-01-28  242  
fc53b4202e61c7e Matt Evans             2010-07-07  243  /* Put the paca pointer into r13 and SPRG_PACA */
7053f80d96967d8 Michael Ellerman       2020-03-20 @244  void __nostackprotector setup_paca(struct paca_struct *new_paca)
fc53b4202e61c7e Matt Evans             2010-07-07  245  {
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  246  	/* Setup r13 */
fc53b4202e61c7e Matt Evans             2010-07-07  247  	local_paca = new_paca;
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  248  
fc53b4202e61c7e Matt Evans             2010-07-07  249  #ifdef CONFIG_PPC_BOOK3E
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  250  	/* On Book3E, initialize the TLB miss exception frames */
fc53b4202e61c7e Matt Evans             2010-07-07  251  	mtspr(SPRN_SPRG_TLB_EXFRAME, local_paca->extlb);
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  252  #else
d4a8e98621543d5 Daniel Axtens          2020-03-20  253  	/*
d4a8e98621543d5 Daniel Axtens          2020-03-20  254  	 * In HV mode, we setup both HPACA and PACA to avoid problems
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  255  	 * if we do a GET_PACA() before the feature fixups have been
d4a8e98621543d5 Daniel Axtens          2020-03-20  256  	 * applied.
d4a8e98621543d5 Daniel Axtens          2020-03-20  257  	 *
d4a8e98621543d5 Daniel Axtens          2020-03-20  258  	 * Normally you should test against CPU_FTR_HVMODE, but CPU features
d4a8e98621543d5 Daniel Axtens          2020-03-20  259  	 * are not yet set up when we first reach here.
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  260  	 */
d4a8e98621543d5 Daniel Axtens          2020-03-20  261  	if (mfmsr() & MSR_HV)
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  262  		mtspr(SPRN_SPRG_HPACA, local_paca);
fc53b4202e61c7e Matt Evans             2010-07-07  263  #endif
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  264  	mtspr(SPRN_SPRG_PACA, local_paca);
2dd60d79e020262 Benjamin Herrenschmidt 2011-01-20  265  
fc53b4202e61c7e Matt Evans             2010-07-07  266  }
fc53b4202e61c7e Matt Evans             2010-07-07  267  
d2e60075a3d4422 Nicholas Piggin        2018-02-14  268  static int __initdata paca_nr_cpu_ids;
d2e60075a3d4422 Nicholas Piggin        2018-02-14  269  static int __initdata paca_ptrs_size;
59f577743d71bf7 Nicholas Piggin        2018-02-14  270  static int __initdata paca_struct_size;
1426d5a3bd07589 Michael Ellerman       2010-01-28  271  
59f577743d71bf7 Nicholas Piggin        2018-02-14  272  void __init allocate_paca_ptrs(void)
59f577743d71bf7 Nicholas Piggin        2018-02-14  273  {
59f577743d71bf7 Nicholas Piggin        2018-02-14 @274  	paca_nr_cpu_ids = nr_cpu_ids;
59f577743d71bf7 Nicholas Piggin        2018-02-14  275  
59f577743d71bf7 Nicholas Piggin        2018-02-14  276  	paca_ptrs_size = sizeof(struct paca_struct *) * nr_cpu_ids;
1269f7b83f2cf79 Christophe Leroy       2019-03-11  277  	paca_ptrs = memblock_alloc_raw(paca_ptrs_size, SMP_CACHE_BYTES);
1269f7b83f2cf79 Christophe Leroy       2019-03-11  278  	if (!paca_ptrs)
1269f7b83f2cf79 Christophe Leroy       2019-03-11  279  		panic("Failed to allocate %d bytes for paca pointers\n",
1269f7b83f2cf79 Christophe Leroy       2019-03-11  280  		      paca_ptrs_size);
1269f7b83f2cf79 Christophe Leroy       2019-03-11  281  
59f577743d71bf7 Nicholas Piggin        2018-02-14  282  	memset(paca_ptrs, 0x88, paca_ptrs_size);
59f577743d71bf7 Nicholas Piggin        2018-02-14  283  }
1426d5a3bd07589 Michael Ellerman       2010-01-28  284

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

[email protected]

2020-10-28 11:48 UTC #4 lore raw

Test Results: RE: powerpc: avoid broken GCC __attribute__((optimize))

In reply to Ard Biesheuvel

Thanks for your contribution, unfortunately we've found some issues.

Your patch was successfully applied on branch powerpc/merge (8cb17737940b156329cb5210669b9c9b23f4dd56)

The test build-ppc64le reported the following: Build failed!

Full log: https://openpower.xyz/job/snowpatch/job/snowpatch-linux-sparse/21048//artifact/linux/report.txt

Here's a preview of the log:

arch/powerpc/kernel/paca.c:244:25: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'setup_paca'
244 | void __nostackprotector setup_paca(struct paca_struct *new_paca)

      |                         ^~~~~~~~~~

make[2]: *** [scripts/Makefile.build:283: arch/powerpc/kernel/paca.o] Error 1 make[1]: *** [scripts/Makefile.build:500: arch/powerpc/kernel] Error 2 make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:1799: arch/powerpc] Error 2
make: *** Waiting for unfinished jobs....

The test build-ppc64be reported the following: Build failed!

Full log: https://openpower.xyz/job/snowpatch/job/snowpatch-linux-sparse/21049//artifact/linux/report.txt

Here's a preview of the log:

arch/powerpc/kernel/paca.c:244:25: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'setup_paca'
244 | void __nostackprotector setup_paca(struct paca_struct *new_paca)

      |                         ^~~~~~~~~~

The test build-ppc64e reported the following: Build failed!

Full log: https://openpower.xyz/job/snowpatch/job/snowpatch-linux-sparse/21050//artifact/linux/report.txt

Here's a preview of the log:

arch/powerpc/kernel/paca.c:244:25: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'setup_paca'
244 | void __nostackprotector setup_paca(struct paca_struct *new_paca)

      |                         ^~~~~~~~~~

Michael Ellerman

Applied

2020-11-25 11:57 UTC #5 lore raw

In reply to Ard Biesheuvel

Quoted 11 lines · Ard Biesheuvel

Commit 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot") introduced a couple of uses of __attribute__((optimize)) with function scope, to disable the stack protector in some early boot code.
Unfortunately, and this is documented in the GCC man pages [0], overriding function attributes for optimization is broken, and is only supported for debug scenarios, not for production: the problem appears to be that setting GCC -f flags using this method will cause it to forget about some or all other optimization settings that have been applied.
[...]

Applied to powerpc/next.

[1/1] powerpc: Avoid broken GCC __attribute__((optimize))

      https://git.kernel.org/powerpc/c/a7223f5bfcaeade4a86d35263493bcda6c940891

cheers