Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 3.12 025/123] ARM: 8429/1: disable GCC SRA optimization | Date | Wed, 28 Oct 2015 14:50:42 +0100 |
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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit a077224fd35b2f7fbc93f14cf67074fc792fbac2 upstream.
While working on the 32-bit ARM port of UEFI, I noticed a strange corruption in the kernel log. The following snprintf() statement (in drivers/firmware/efi/efi.c:efi_md_typeattr_format())
snprintf(pos, size, "|%3s|%2s|%2s|%2s|%3s|%2s|%2s|%2s|%2s]",
was producing the following output in the log:
| | | | | |WB|WT|WC|UC] | | | | | |WB|WT|WC|UC] | | | | | |WB|WT|WC|UC] |RUN| | | | |WB|WT|WC|UC]* |RUN| | | | |WB|WT|WC|UC]* | | | | | |WB|WT|WC|UC] |RUN| | | | |WB|WT|WC|UC]* | | | | | |WB|WT|WC|UC] |RUN| | | | | | | |UC] |RUN| | | | | | | |UC]
As it turns out, this is caused by incorrect code being emitted for the string() function in lib/vsprintf.c. The following code
if (!(spec.flags & LEFT)) { while (len < spec.field_width--) { if (buf < end) *buf = ' '; ++buf; } } for (i = 0; i < len; ++i) { if (buf < end) *buf = *s; ++buf; ++s; } while (len < spec.field_width--) { if (buf < end) *buf = ' '; ++buf; }
when called with len == 0, triggers an issue in the GCC SRA optimization pass (Scalar Replacement of Aggregates), which handles promotion of signed struct members incorrectly. This is a known but as yet unresolved issue. (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65932). In this particular case, it is causing the second while loop to be executed erroneously a single time, causing the additional space characters to be printed.
So disable the optimization by passing -fno-ipa-sra.
Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Jiri Slaby <jslaby@suse.cz> --- arch/arm/Makefile | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/arm/Makefile b/arch/arm/Makefile index db50b626be98..a4254e8ab36c 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -55,6 +55,14 @@ endif comma = , +# +# The Scalar Replacement of Aggregates (SRA) optimization pass in GCC 4.9 and +# later may result in code being generated that handles signed short and signed +# char struct members incorrectly. So disable it. +# (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65932) +# +KBUILD_CFLAGS += $(call cc-option,-fno-ipa-sra) + # This selects which instruction set is used. # Note that GCC does not numerically define an architecture version # macro, but instead defines a whole series of macros which makes -- 2.6.2
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