[Buildroot] [PATCH v3 1/1] qemu: add patch to fix SSP support detection

[Buildroot] [PATCH v3 1/1] qemu: add patch to fix SSP support detection

[Rodrigo Rebello]

The QEMU configure script incorrectly assumes SSP is supported by the
toolchain in some cases where the compiler accepts -fstack-protector*
flags but the C library does not provide the necessary __stack_chk_*()
functions.

Even though a full compile and link test is performed by the script,
this is done with a code fragment which does not actually meet any of
the conditions required to cause the compiler to emit canary code when
the -fstack-protector-strong variant is used. As no compile or link
failure occurs in this case, a false positive is generated and a
subsequent error is seen when the probe for pthreads is performed.

The fix consists in patching the configure script to use a more
appropriate test program for the SSP support checks.

Fixes:

  http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
  http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
  http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
  ...and many others.

Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
---
Changes v2 -> v3:
  - Use a better test code fragment that works when LTO is enabled

Changes v1 -> v2:
  - Patch the configure script instead of force disable SSP detection
    (Arnout Vandecappelle)
---
 ...se-appropriate-code-fragment-for-fstack-p.patch | 58 ++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch

diff --git a/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch b/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
new file mode 100644
index 0000000..9ebe334
--- /dev/null
+++ b/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
@@ -0,0 +1,58 @@
+From 7b93e98143c376ed09bfd30658b8641d4a36e77e Mon Sep 17 00:00:00 2001
+From: Rodrigo Rebello <rprebello@gmail.com>
+Date: Thu, 12 Nov 2015 12:04:28 -0200
+Subject: [PATCH] configure: use appropriate code fragment for
+ -fstack-protector checks
+Cc: qemu-trivial at nongnu.org
+
+The check for stack-protector support consisted in compiling and linking
+the test program below (output by function write_c_skeleton()) with the
+compiler flag -fstack-protector-strong first and then with
+-fstack-protector-all if the first one failed to work:
+
+  int main(void) { return 0; }
+
+This caused false positives when using certain toolchains in which the
+compiler accepts -fstack-protector-strong but no support is provided by
+the C library, since in this stack-protector variant the compiler emits
+canary code only for functions that meet specific conditions (local
+arrays, memory references to local variables, etc.) and the code
+fragment under test included none of them (hence no stack protection
+code generated, no link failure).
+
+This fix modifies the test program used for -fstack-protector checks to
+meet conditions which cause the compiler to generate canary code in all
+variants.
+
+Upstream status: sent
+https://patchwork.ozlabs.org/patch/543357/
+
+Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
+---
+ configure | 10 ++++++++++
+ 1 file changed, 10 insertions(+)
+
+diff --git a/configure b/configure
+index cd219d8..27d7b3c 100755
+--- a/configure
++++ b/configure
+@@ -1471,6 +1471,16 @@ for flag in $gcc_flags; do
+ done
+ 
+ if test "$stack_protector" != "no"; then
++  cat > $TMPC << EOF
++int main(int argc, char *argv[])
++{
++    char arr[64], *p = arr, *c = argv[0];
++    while (*c) {
++        *p++ = *c++;
++    }
++    return 0;
++}
++EOF
+   gcc_flags="-fstack-protector-strong -fstack-protector-all"
+   sp_on=0
+   for flag in $gcc_flags; do
+-- 
+2.1.4
+
-- 
2.1.4

[Buildroot] [PATCH v3 1/1] qemu: add patch to fix SSP support detection

[Arnout Vandecappelle]

On 16-11-15 11:58, Rodrigo Rebello wrote:
> The QEMU configure script incorrectly assumes SSP is supported by the
> toolchain in some cases where the compiler accepts -fstack-protector*
> flags but the C library does not provide the necessary __stack_chk_*()
> functions.
> 
> Even though a full compile and link test is performed by the script,
> this is done with a code fragment which does not actually meet any of
> the conditions required to cause the compiler to emit canary code when
> the -fstack-protector-strong variant is used. As no compile or link
> failure occurs in this case, a false positive is generated and a
> subsequent error is seen when the probe for pthreads is performed.
> 
> The fix consists in patching the configure script to use a more
> appropriate test program for the SSP support checks.
> 
> Fixes:
> 
>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>   ...and many others.
> 
> Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>

Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
 (untested)

 Is the patch for the toolchain wrapper also coming?

 Regards,
 Arnout

> ---
> Changes v2 -> v3:
>   - Use a better test code fragment that works when LTO is enabled
> 
> Changes v1 -> v2:
>   - Patch the configure script instead of force disable SSP detection
>     (Arnout Vandecappelle)
> ---
>  ...se-appropriate-code-fragment-for-fstack-p.patch | 58 ++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
>  create mode 100644 package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
> 
> diff --git a/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch b/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
> new file mode 100644
> index 0000000..9ebe334
> --- /dev/null
> +++ b/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
> @@ -0,0 +1,58 @@
> +From 7b93e98143c376ed09bfd30658b8641d4a36e77e Mon Sep 17 00:00:00 2001
> +From: Rodrigo Rebello <rprebello@gmail.com>
> +Date: Thu, 12 Nov 2015 12:04:28 -0200
> +Subject: [PATCH] configure: use appropriate code fragment for
> + -fstack-protector checks
> +Cc: qemu-trivial at nongnu.org
> +
> +The check for stack-protector support consisted in compiling and linking
> +the test program below (output by function write_c_skeleton()) with the
> +compiler flag -fstack-protector-strong first and then with
> +-fstack-protector-all if the first one failed to work:
> +
> +  int main(void) { return 0; }
> +
> +This caused false positives when using certain toolchains in which the
> +compiler accepts -fstack-protector-strong but no support is provided by
> +the C library, since in this stack-protector variant the compiler emits
> +canary code only for functions that meet specific conditions (local
> +arrays, memory references to local variables, etc.) and the code
> +fragment under test included none of them (hence no stack protection
> +code generated, no link failure).
> +
> +This fix modifies the test program used for -fstack-protector checks to
> +meet conditions which cause the compiler to generate canary code in all
> +variants.
> +
> +Upstream status: sent
> +https://patchwork.ozlabs.org/patch/543357/
> +
> +Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
> +---
> + configure | 10 ++++++++++
> + 1 file changed, 10 insertions(+)
> +
> +diff --git a/configure b/configure
> +index cd219d8..27d7b3c 100755
> +--- a/configure
> ++++ b/configure
> +@@ -1471,6 +1471,16 @@ for flag in $gcc_flags; do
> + done
> + 
> + if test "$stack_protector" != "no"; then
> ++  cat > $TMPC << EOF
> ++int main(int argc, char *argv[])
> ++{
> ++    char arr[64], *p = arr, *c = argv[0];
> ++    while (*c) {
> ++        *p++ = *c++;
> ++    }
> ++    return 0;
> ++}
> ++EOF
> +   gcc_flags="-fstack-protector-strong -fstack-protector-all"
> +   sp_on=0
> +   for flag in $gcc_flags; do
> +-- 
> +2.1.4
> +
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH v3 1/1] qemu: add patch to fix SSP support detection

[Rodrigo Rebello]

Arnout,

2015-11-16 18:09 GMT-02:00 Arnout Vandecappelle <arnout@mind.be>:
[snip]
>
> Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
>  (untested)
>
>  Is the patch for the toolchain wrapper also coming?
>

Yes, I'll submit it as soon as I get home.

Regards,
Rodrigo

>  Regards,
>  Arnout
>
>> ---
>> Changes v2 -> v3:
>>   - Use a better test code fragment that works when LTO is enabled
>>
>> Changes v1 -> v2:
>>   - Patch the configure script instead of force disable SSP detection
>>     (Arnout Vandecappelle)
>> ---
>>  ...se-appropriate-code-fragment-for-fstack-p.patch | 58 ++++++++++++++++++++++
>>  1 file changed, 58 insertions(+)
>>  create mode 100644 package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
>>
>> diff --git a/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch b/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
>> new file mode 100644
>> index 0000000..9ebe334
>> --- /dev/null
>> +++ b/package/qemu/0001-configure-use-appropriate-code-fragment-for-fstack-p.patch
>> @@ -0,0 +1,58 @@
>> +From 7b93e98143c376ed09bfd30658b8641d4a36e77e Mon Sep 17 00:00:00 2001
>> +From: Rodrigo Rebello <rprebello@gmail.com>
>> +Date: Thu, 12 Nov 2015 12:04:28 -0200
>> +Subject: [PATCH] configure: use appropriate code fragment for
>> + -fstack-protector checks
>> +Cc: qemu-trivial at nongnu.org
>> +
>> +The check for stack-protector support consisted in compiling and linking
>> +the test program below (output by function write_c_skeleton()) with the
>> +compiler flag -fstack-protector-strong first and then with
>> +-fstack-protector-all if the first one failed to work:
>> +
>> +  int main(void) { return 0; }
>> +
>> +This caused false positives when using certain toolchains in which the
>> +compiler accepts -fstack-protector-strong but no support is provided by
>> +the C library, since in this stack-protector variant the compiler emits
>> +canary code only for functions that meet specific conditions (local
>> +arrays, memory references to local variables, etc.) and the code
>> +fragment under test included none of them (hence no stack protection
>> +code generated, no link failure).
>> +
>> +This fix modifies the test program used for -fstack-protector checks to
>> +meet conditions which cause the compiler to generate canary code in all
>> +variants.
>> +
>> +Upstream status: sent
>> +https://patchwork.ozlabs.org/patch/543357/
>> +
>> +Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
>> +---
>> + configure | 10 ++++++++++
>> + 1 file changed, 10 insertions(+)
>> +
>> +diff --git a/configure b/configure
>> +index cd219d8..27d7b3c 100755
>> +--- a/configure
>> ++++ b/configure
>> +@@ -1471,6 +1471,16 @@ for flag in $gcc_flags; do
>> + done
>> +
>> + if test "$stack_protector" != "no"; then
>> ++  cat > $TMPC << EOF
>> ++int main(int argc, char *argv[])
>> ++{
>> ++    char arr[64], *p = arr, *c = argv[0];
>> ++    while (*c) {
>> ++        *p++ = *c++;
>> ++    }
>> ++    return 0;
>> ++}
>> ++EOF
>> +   gcc_flags="-fstack-protector-strong -fstack-protector-all"
>> +   sp_on=0
>> +   for flag in $gcc_flags; do
>> +--
>> +2.1.4
>> +
>>
>
>
> --
> Arnout Vandecappelle                          arnout at mind be
> Senior Embedded Software Architect            +32-16-286500
> Essensium/Mind                                http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
> LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
> GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH v3 1/1] qemu: add patch to fix SSP support detection

[Vicente Olivert Riera]

Dear Rodrigo Rebello,

On 11/16/2015 10:58 AM, Rodrigo Rebello wrote:
> The QEMU configure script incorrectly assumes SSP is supported by the
> toolchain in some cases where the compiler accepts -fstack-protector*
> flags but the C library does not provide the necessary __stack_chk_*()
> functions.
> 
> Even though a full compile and link test is performed by the script,
> this is done with a code fragment which does not actually meet any of
> the conditions required to cause the compiler to emit canary code when
> the -fstack-protector-strong variant is used. As no compile or link
> failure occurs in this case, a false positive is generated and a
> subsequent error is seen when the probe for pthreads is performed.
> 
> The fix consists in patching the configure script to use a more
> appropriate test program for the SSP support checks.
> 
> Fixes:
> 
>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>   ...and many others.
> 
> Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
Reviewed-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Tested-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>

Build test for MIPS architecture. This patch fixed this recent autobuild
failure:

http://autobuild.buildroot.net/results/9a7211e7b40f5a08fc50a912663d53af515896a8/

Regards,

Vincent.

[Buildroot] [PATCH v3 1/1] qemu: add patch to fix SSP support detection

[Thomas Petazzoni]

Dear Rodrigo Rebello,

On Mon, 16 Nov 2015 08:58:18 -0200, Rodrigo Rebello wrote:
> The QEMU configure script incorrectly assumes SSP is supported by the
> toolchain in some cases where the compiler accepts -fstack-protector*
> flags but the C library does not provide the necessary __stack_chk_*()
> functions.
> 
> Even though a full compile and link test is performed by the script,
> this is done with a code fragment which does not actually meet any of
> the conditions required to cause the compiler to emit canary code when
> the -fstack-protector-strong variant is used. As no compile or link
> failure occurs in this case, a false positive is generated and a
> subsequent error is seen when the probe for pthreads is performed.
> 
> The fix consists in patching the configure script to use a more
> appropriate test program for the SSP support checks.
> 
> Fixes:
> 
>   http://autobuild.buildroot.net/results/efb/efbb4e940543894b8745bb405478a096c90a5ae2/
>   http://autobuild.buildroot.net/results/32d/32d6d984febad2dee1f0d31c5fa0aea823297096/
>   http://autobuild.buildroot.net/results/aa6/aa6e71c957fb6f07e7bded35a8e47be4dadd042c/
>   ...and many others.
> 
> Signed-off-by: Rodrigo Rebello <rprebello@gmail.com>
> ---
> Changes v2 -> v3:
>   - Use a better test code fragment that works when LTO is enabled

Applied to master, thanks.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com