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a18006390c
commit a077224fd3 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>