Since commit cafa0010cd ("Raise the minimum required gcc version
to 4.6"), the kernel can no longer be compiled using gcc-3.
Hence __div64_const32_is_OK() is always true.
Moreover, __div64_const32_is_OK() is defined in the same way in
include/asm-generic/div64.h, so the ARM-specific definition can be
removed regardless.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
The ARM version of __div64_32() encapsulates a call to __do_div64 with
non-standard argument passing. In particular, __n is a 64-bit input
argument assigned to r0-r1 and __rem is an output argument sharing half
of that r0-r1 register pair.
With __n being an input argument, the compiler is in its right to
presume that r0-r1 would still hold the value of __n past the inline
assembly statement. Normally, the compiler would have assigned non
overlapping registers to __n and __rem if the value for __n is needed
again.
However, here we enforce our own register assignment and gcc fails to
notice the conflict. In practice this doesn't cause any problem as __n
is considered dead after the asm statement and *n is overwritten.
However this is not always guaranteed and clang rightfully complains.
Let's fix it properly by making __n into an input-output variable. This
makes it clear that those registers representing __n have been modified.
Then we can extract __rem as the high part of __n with plain C code.
This asm constraint "abuse" was likely relied upon back when gcc didn't
handle 64-bit values optimally. Turns out that gcc is now able to
optimize things and produces the same code with this patch applied.
Reported-by: Antony Yu <swpenim@gmail.com>
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tmp variable is used twice: first to pose as a register containing
a value of zero, and then to provide a temporary register that initially
is zero and get added some value. But somehow gcc decides to split those
two usages in different registers.
Example code:
u64 div64const1000(u64 x)
{
u32 y = 1000;
do_div(x, y);
return x;
}
Result:
div64const1000:
push {r4, r5, r6, r7, lr}
mov lr, #0
mov r6, r0
mov r7, r1
adr r5, .L8
ldrd r4, [r5]
mov r1, lr
umull r2, r3, r4, r6
cmn r2, r4
adcs r3, r3, r5
adc r2, lr, #0
umlal r3, r2, r5, r6
umlal r3, r1, r4, r7
mov r3, #0
adds r2, r1, r2
adc r3, r3, #0
umlal r2, r3, r5, r7
lsr r0, r2, #9
lsr r1, r3, #9
orr r0, r0, r3, lsl #23
pop {r4, r5, r6, r7, pc}
.align 3
.L8:
.word -1924145349
.word -2095944041
Full kernel build size:
text data bss dec hex filename
13663814 1553940 351368 15569122 ed90e2 vmlinux
Here the two instances of 'tmp' are assigned to r1 and lr.
To avoid that, let's mark the first 'tmp' usage in __arch_xprod_64()
with a "+r" constraint even if the register is not written to, so to
create a dependency for the second usage with the effect of enforcing
a single temporary register throughout.
Result:
div64const1000:
push {r4, r5, r6, r7}
movs r3, #0
adr r5, .L8
ldrd r4, [r5]
umull r6, r7, r4, r0
cmn r6, r4
adcs r7, r7, r5
adc r6, r3, #0
umlal r7, r6, r5, r0
umlal r7, r3, r4, r1
mov r7, #0
adds r6, r3, r6
adc r7, r7, #0
umlal r6, r7, r5, r1
lsr r0, r6, #9
lsr r1, r7, #9
orr r0, r0, r7, lsl #23
pop {r4, r5, r6, r7}
bx lr
.align 3
.L8:
.word -1924145349
.word -2095944041
text data bss dec hex filename
13663438 1553940 351368 15568746 ed8f6a vmlinux
This time 'tmp' is assigned to r3 and used throughout. However, by being
assigned to r3, that blocks usage of the r2-r3 double register slot for
64-bit values, forcing more registers to be spilled on the stack. Let's
try to help it by forcing 'tmp' to the caller-saved ip register.
Result:
div64const1000:
stmfd sp!, {r4, r5}
mov ip, #0
adr r5, .L8
ldrd r4, [r5]
umull r2, r3, r4, r0
cmn r2, r4
adcs r3, r3, r5
adc r2, ip, #0
umlal r3, r2, r5, r0
umlal r3, ip, r4, r1
mov r3, #0
adds r2, ip, r2
adc r3, r3, #0
umlal r2, r3, r5, r1
mov r0, r2, lsr #9
mov r1, r3, lsr #9
orr r0, r0, r3, asl #23
ldmfd sp!, {r4, r5}
bx lr
.align 3
.L8:
.word -1924145349
.word -2095944041
text data bss dec hex filename
13662838 1553940 351368 15568146 ed8d12 vmlinux
We could make the code marginally smaller yet by forcing 'tmp' to lr
instead, but that would have a negative inpact on branch prediction for
which "bx lr" is optimal.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
In big-endian systems, "%1" get the most significant part of the value, cause the instruction to get the wrong result.
When viewing ftrace record in big-endian ARM systems, we found that
the timestamp errors:
swapper-0 [001] 1325.970000: 0:120:R ==> [001] 16:120:R events/1
events/1-16 [001] 1325.970000: 16:120:S ==> [001] 0:120:R swapper
swapper-0 [000] 1325.1000000: 0:120:R + [000] 15:120:R events/0
swapper-0 [000] 1325.1000000: 0:120:R ==> [000] 15:120:R events/0
swapper-0 [000] 1326.030000: 0:120:R + [000] 1150:120:R sshd
swapper-0 [000] 1326.030000: 0:120:R ==> [000] 1150:120:R sshd
When viewed ftrace records, it will call the do_div(n, base) function, which achieved arch/arm/include/asm/div64.h in. When n = 10000000, base = 1000000, in do_div(n, base) will execute "umull %Q0, %R0, %1, %Q2".
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Cc: <stable@vger.kernel.org> # 2.6.20+
Signed-off-by: Alex Wu <wuquanming@huawei.com>
Signed-off-by: Xiangyu Lu <luxiangyu@huawei.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
In OABI configurations, some uses of the do_div function
cause gcc to run out of registers. To work around that,
we can force the use of the out-of-line version for
configurations that build a OABI kernel.
Without this patch, building netx_defconfig results in:
net/core/pktgen.c: In function 'pktgen_if_show':
net/core/pktgen.c:682:2775: error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'
net/core/pktgen.c:682:3153: error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'
net/core/pktgen.c:682:2775: error: 'asm' operand has impossible constraints
net/core/pktgen.c:682:3153: error: 'asm' operand has impossible constraints
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Disintegrate asm/system.h for ARM.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Russell King <linux@arm.linux.org.uk>
cc: linux-arm-kernel@lists.infradead.org
Those inline assembly segments using the umlal instruction must have
the & modifier so to be sure that a purely input register won't alias
one of the registers used as input+output. In most cases, the inputs
are still used after the outputs are touched, and most binutil versions
insist on "rdhi, rdlo and rm must all be different" even for ARMv6+.
Signed-off-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Move platform independent header files to arch/arm/include/asm, leaving
those in asm/arch* and asm/plat* alone.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Geert Uytterhoeven
Nicolas Pitre
Greg Kroah-Hartman
Nicolas Pitre
Xiangyu Lu
Arnd Bergmann
David Howells
Nicolas Pitre
Russell King