* [Buildroot] [PATCH] mbedtls: fix x86 PIC build with GCC < 5
@ 2018-08-27 21:16 Peter Korsgaard
2018-08-28 7:54 ` Peter Korsgaard
2018-08-28 8:13 ` Peter Korsgaard
0 siblings, 2 replies; 3+ messages in thread
From: Peter Korsgaard @ 2018-08-27 21:16 UTC (permalink / raw)
To: buildroot
Fixes:
http://autobuild.buildroot.net/results/d6d/d6dc9a640aa1f6650a3e7b9397f2fe2ae3433f4d/
http://autobuild.buildroot.net/results/ab5/ab5a58ea7845f9f378454ee1aa7e872448618ba9/
ebx was recently added to the x86 inline asm MULADDC_STOP clobber list to
fix #1550, but this causes the build to fail with GCC < 5 when building in
PIC mode with errors like:
include/mbedtls/bn_mul.h:46:13: error: PIC register clobbered by ?ebx? in ?asm?
This is because older GCC versions treated the x86 ebx register (which is
used for the GOT) as a fixed reserved register when building as PIC.
This is fixed by an improved register allocator in GCC 5+. From the release
notes:
Register allocation improvements: Reuse of the PIC hard register, instead of
using a fixed register, was implemented on x86/x86-64 targets. This
improves generated PIC code performance as more hard registers can be used.
https://www.gnu.org/software/gcc/gcc-5/changes.html
As a workaround, add a patch to detect this situation and disable the inline
assembly, similar to the MULADDC_CANNOT_USE_R7 logic.
Patch submitted upstream: https://github.com/ARMmbed/mbedtls/pull/1986
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
...x-x86-PIC-inline-ASM-compilation-with-GCC.patch | 74 ++++++++++++++++++++++
1 file changed, 74 insertions(+)
create mode 100644 package/mbedtls/0001-bn_mul.h-fix-x86-PIC-inline-ASM-compilation-with-GCC.patch
diff --git a/package/mbedtls/0001-bn_mul.h-fix-x86-PIC-inline-ASM-compilation-with-GCC.patch b/package/mbedtls/0001-bn_mul.h-fix-x86-PIC-inline-ASM-compilation-with-GCC.patch
new file mode 100644
index 0000000000..60bf53f6e4
--- /dev/null
+++ b/package/mbedtls/0001-bn_mul.h-fix-x86-PIC-inline-ASM-compilation-with-GCC.patch
@@ -0,0 +1,74 @@
+From a0ae2ba37ca479c6edddec8634b25686be965e0d Mon Sep 17 00:00:00 2001
+From: Peter Korsgaard <peter@korsgaard.com>
+Date: Mon, 27 Aug 2018 22:50:57 +0200
+Subject: [PATCH] bn_mul.h: fix x86 PIC inline ASM compilation with GCC < 5
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Fixes #1910
+
+With ebx added to the MULADDC_STOP clobber list to fix #1550, the inline
+assembly fails to build with GCC < 5 in PIC mode with the following error:
+
+include/mbedtls/bn_mul.h:46:13: error: PIC register clobbered by ?ebx? in ?asm?
+
+This is because older GCC versions treated the x86 ebx register (which is
+used for the GOT) as a fixed reserved register when building as PIC.
+
+This is fixed by an improved register allocator in GCC 5+. From the release
+notes:
+
+Register allocation improvements: Reuse of the PIC hard register, instead of
+using a fixed register, was implemented on x86/x86-64 targets. This
+improves generated PIC code performance as more hard registers can be used.
+
+https://www.gnu.org/software/gcc/gcc-5/changes.html
+
+As a workaround, detect this situation and disable the inline assembly,
+similar to the MULADDC_CANNOT_USE_R7 logic.
+
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+Upstream: https://github.com/ARMmbed/mbedtls/pull/1986
+---
+ include/mbedtls/bn_mul.h | 18 +++++++++++++++++-
+ 1 file changed, 17 insertions(+), 1 deletion(-)
+
+diff --git a/include/mbedtls/bn_mul.h b/include/mbedtls/bn_mul.h
+index b587317d9..74a2d29be 100644
+--- a/include/mbedtls/bn_mul.h
++++ b/include/mbedtls/bn_mul.h
+@@ -50,13 +50,29 @@
+ #if defined(__GNUC__) && \
+ ( !defined(__ARMCC_VERSION) || __ARMCC_VERSION >= 6000000 )
+
++/*
++ * GCC < 5.0 treated the x86 ebx (which is used for the GOT) as a
++ * fixed reserved register when building as PIC, leading to errors
++ * like: bn_mul.h:46:13: error: PIC register clobbered by ?ebx? in ?asm?
++ *
++ * This is fixed by an improved register allocator in GCC 5+. From the
++ * release notes:
++ * Register allocation improvements: Reuse of the PIC hard register,
++ * instead of using a fixed register, was implemented on x86/x86-64
++ * targets. This improves generated PIC code performance as more hard
++ * registers can be used.
++ */
++#if defined(__GNUC__) && __GNUC__ < 5 && defined(__PIC__)
++#define MULADDC_CANNOT_USE_EBX
++#endif
++
+ /*
+ * Disable use of the i386 assembly code below if option -O0, to disable all
+ * compiler optimisations, is passed, detected with __OPTIMIZE__
+ * This is done as the number of registers used in the assembly code doesn't
+ * work with the -O0 option.
+ */
+-#if defined(__i386__) && defined(__OPTIMIZE__)
++#if defined(__i386__) && defined(__OPTIMIZE__) && !defined(MULADDC_CANNOT_USE_EBX)
+
+ #define MULADDC_INIT \
+ asm( \
+--
+2.11.0
+
--
2.11.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [Buildroot] [PATCH] mbedtls: fix x86 PIC build with GCC < 5
2018-08-27 21:16 [Buildroot] [PATCH] mbedtls: fix x86 PIC build with GCC < 5 Peter Korsgaard
@ 2018-08-28 7:54 ` Peter Korsgaard
2018-08-28 8:13 ` Peter Korsgaard
1 sibling, 0 replies; 3+ messages in thread
From: Peter Korsgaard @ 2018-08-28 7:54 UTC (permalink / raw)
To: buildroot
>>>>> "Peter" == Peter Korsgaard <peter@korsgaard.com> writes:
> Fixes:
> http://autobuild.buildroot.net/results/d6d/d6dc9a640aa1f6650a3e7b9397f2fe2ae3433f4d/
> http://autobuild.buildroot.net/results/ab5/ab5a58ea7845f9f378454ee1aa7e872448618ba9/
> ebx was recently added to the x86 inline asm MULADDC_STOP clobber list to
> fix #1550, but this causes the build to fail with GCC < 5 when building in
> PIC mode with errors like:
> include/mbedtls/bn_mul.h:46:13: error: PIC register clobbered by ?ebx? in ?asm?
> This is because older GCC versions treated the x86 ebx register (which is
> used for the GOT) as a fixed reserved register when building as PIC.
> This is fixed by an improved register allocator in GCC 5+. From the release
> notes:
> Register allocation improvements: Reuse of the PIC hard register, instead of
> using a fixed register, was implemented on x86/x86-64 targets. This
> improves generated PIC code performance as more hard registers can be used.
> https://www.gnu.org/software/gcc/gcc-5/changes.html
> As a workaround, add a patch to detect this situation and disable the inline
> assembly, similar to the MULADDC_CANNOT_USE_R7 logic.
> Patch submitted upstream: https://github.com/ARMmbed/mbedtls/pull/1986
> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Committed, thanks.
--
Bye, Peter Korsgaard
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Buildroot] [PATCH] mbedtls: fix x86 PIC build with GCC < 5
2018-08-27 21:16 [Buildroot] [PATCH] mbedtls: fix x86 PIC build with GCC < 5 Peter Korsgaard
2018-08-28 7:54 ` Peter Korsgaard
@ 2018-08-28 8:13 ` Peter Korsgaard
1 sibling, 0 replies; 3+ messages in thread
From: Peter Korsgaard @ 2018-08-28 8:13 UTC (permalink / raw)
To: buildroot
>>>>> "Peter" == Peter Korsgaard <peter@korsgaard.com> writes:
> Fixes:
> http://autobuild.buildroot.net/results/d6d/d6dc9a640aa1f6650a3e7b9397f2fe2ae3433f4d/
> http://autobuild.buildroot.net/results/ab5/ab5a58ea7845f9f378454ee1aa7e872448618ba9/
> ebx was recently added to the x86 inline asm MULADDC_STOP clobber list to
> fix #1550, but this causes the build to fail with GCC < 5 when building in
> PIC mode with errors like:
> include/mbedtls/bn_mul.h:46:13: error: PIC register clobbered by ?ebx? in ?asm?
> This is because older GCC versions treated the x86 ebx register (which is
> used for the GOT) as a fixed reserved register when building as PIC.
> This is fixed by an improved register allocator in GCC 5+. From the release
> notes:
> Register allocation improvements: Reuse of the PIC hard register, instead of
> using a fixed register, was implemented on x86/x86-64 targets. This
> improves generated PIC code performance as more hard registers can be used.
> https://www.gnu.org/software/gcc/gcc-5/changes.html
> As a workaround, add a patch to detect this situation and disable the inline
> assembly, similar to the MULADDC_CANNOT_USE_R7 logic.
> Patch submitted upstream: https://github.com/ARMmbed/mbedtls/pull/1986
> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Committed to 2018.02.x and 2018.05.x, thanks.
--
Bye, Peter Korsgaard
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-08-27 21:16 [Buildroot] [PATCH] mbedtls: fix x86 PIC build with GCC < 5 Peter Korsgaard
2018-08-28 7:54 ` Peter Korsgaard
2018-08-28 8:13 ` Peter Korsgaard
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