Older versions of bintutils do not allow symbol math across different
segments on sparc:
====================
Assembler messages:
99: Error: operation combines symbols in different segments
====================
This is controlled by whether or not DIFF_EXPR_OK is defined in
gas/config/tc-*.h and for sparc this was not the case until mid-2017.
So we have to patch between %stick and %tick another way.
Do what powerpc does and emit two versions of the relevant functions,
one using %tick and one using %stick, and patch the symbols in the
dynamic symbol table.
Fixes: 2f6c9bf31a ("sparc: Improve VDSO instruction patching.")
Reported-by: Meelis Roos <mroos@linux.ee>
Tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: David S. Miller <davem@davemloft.net>
Almost entirely borrowed from the x86 code.
Main improvement is to avoid having to initialize
ts->tv_nsec to zero before the sequence loops, by
expanding timespec_add_ns().
Signed-off-by: David S. Miller <davem@davemloft.net>
There should be no undefined symbols in the resulting VDSO image(s).
On sparc, fixed register usage can result in undefined symbols ending
up in the image. To combat this, we do two things:
1) Define current_thread_info() specially when BUILD_DSO.
2) Ignore "#scratch" register undefined symbols in the output.
Signed-off-by: David S. Miller <davem@davemloft.net>
Rather than funneling through CC.
Also, use --hash-style=both just like other VDSO architectures and
glibc do.
Signed-off-by: David S. Miller <davem@davemloft.net>
Do not set any special register usage options, use the default which
is exactly what we should use for userspace code.
Make sure we remove the gcc plugin options from the 64-bit build.
The 32-bit cflags got it right already.
Signed-off-by: David S. Miller <davem@davemloft.net>
If the TICK_PRIV_BIT was set, we would not be able to read the tick
register in user space, which is where this code runs.
Signed-off-by: David S. Miller <davem@davemloft.net>
One interesting thing we need to do is stop using
__builtin_return_address() in get_vvar_data().
Simply read the %pc register instead.
Signed-off-by: David S. Miller <davem@davemloft.net>
The current VDSO patch mechanism has several problems:
1) It assumes how gcc will emit a function, with a register
window, an initial save instruction and then immediately
the %tick read when compiling vread_tick().
There is no such guarantees, code generation could change
at any time, gcc could put a nop between the save and
the %tick read, etc.
So this is extremely fragile and would fail some day.
2) It disallows us to properly inline vread_tick() into the callers
and thus get the best possible code sequences.
So fix this to patch properly, with location based annotations.
We have to be careful because we cannot do it the way we do
patches elsewhere in the kernel. Those use a sequence like:
1:
insn
.section .whatever_patch, "ax"
.word 1b
replacement_insn
.previous
This is a dynamic shared object, so that .word cannot be resolved at
build time, and thus cannot be used to execute the patches when the
kernel initializes the images.
Even trying to use label difference equations doesn't work in the
above kind of scheme:
1:
insn
.section .whatever_patch, "ax"
.word . - 1b
replacement_insn
.previous
The assembler complains that it cannot resolve that computation.
The issue is that this is contained in an executable section.
Borrow the sequence used by x86 alternatives, which is:
1:
insn
.pushsection .whatever_patch, "a"
.word . - 1b, . - 1f
.popsection
.pushsection .whatever_patch_replacements, "ax"
1:
replacement_insn
.previous
This works, allows us to inline vread_tick() as much as we like, and
can be used for arbitrary kinds of VDSO patching in the future.
Also, reverse the condition for patching. Most systems are %stick
based, so if we only patch on %tick systems the patching code will
get little or no testing.
Signed-off-by: David S. Miller <davem@davemloft.net>
Smatch complains that "val" would be uninitialized if kstrtoul() fails.
Fixes: 9a08862a5d ("vDSO for sparc")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
First, the trap number for 32-bit syscalls is 0x10.
Also, only negate the return value when syscall error is indicated by
the carry bit being set.
Signed-off-by: David S. Miller <davem@davemloft.net>
arch/sparc/vdso/Makefile is a replica of arch/x86/entry/vdso/Makefile.
Clean-up the Makefile in the same way as I did for x86:
- Remove unnecessary export
- Put the generated linker script to $(obj)/ instead of $(src)/
- Simplify cmd_vdso2c
The corresponding x86 commits are:
- 61615faf0a ("x86/build/vdso: Remove unnecessary export in Makefile")
- 1742ed2088 ("x86/build/vdso: Put generated linker scripts to $(obj)/")
- c5fcdbf155 ("x86/build/vdso: Simplify 'cmd_vdso2c'")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
GNU Make automatically deletes intermediate files that are updated
in a chain of pattern rules.
Example 1) %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
Example 2) %.o <- %.c <- %.c_shipped
A couple of makefiles mark such targets as .PRECIOUS to prevent Make
from deleting them, but the correct way is to use .SECONDARY.
.SECONDARY
Prerequisites of this special target are treated as intermediate
files but are never automatically deleted.
.PRECIOUS
When make is interrupted during execution, it may delete the target
file it is updating if the file was modified since make started.
If you mark the file as precious, make will never delete the file
if interrupted.
Both can avoid deletion of intermediate files, but the difference is
the behavior when Make is interrupted; .SECONDARY deletes the target,
but .PRECIOUS does not.
The use of .PRECIOUS is relatively rare since we do not want to keep
partially constructed (possibly corrupted) targets.
Another difference is that .PRECIOUS works with pattern rules whereas
.SECONDARY does not.
.PRECIOUS: $(obj)/%.lex.c
works, but
.SECONDARY: $(obj)/%.lex.c
has no effect. However, for the reason above, I do not want to use
.PRECIOUS which could cause obscure build breakage.
The targets specified as .SECONDARY must be explicit. $(targets)
contains all targets that need to include .*.cmd files. So, the
intermediates you want to keep are mostly in there. Therefore, mark
$(targets) as .SECONDARY. It means primary targets are also marked
as .SECONDARY, but I do not see any drawback for this.
I replaced some .SECONDARY / .PRECIOUS markers with 'targets'. This
will make Kbuild search for non-existing .*.cmd files, but this is
not a noticeable performance issue.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Frank Rowand <frowand.list@gmail.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
This statement is indented one tab too far which is confusing and
leads to a Smatch warning:
arch/sparc/vdso/vma.c:254 arch_setup_additional_pages()
warn: curly braces intended?
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Nagarathnam Muthusamy <nagarathnam.muthusamy@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Following patch is based on work done by Nick Alcock on 64-bit vDSO for sparc
in Oracle linux. I have extended it to include support for 32-bit vDSO for sparc
on 64-bit kernel.
vDSO for sparc is based on the X86 implementation. This patch
provides vDSO support for both 64-bit and 32-bit programs on 64-bit kernel.
vDSO will be disabled on 32-bit linux kernel on sparc.
*) vclock_gettime.c contains all the vdso functions. Since data page is mapped
before the vdso code page, the pointer to data page is got by subracting offset
from an address in the vdso code page. The return address stored in
%i7 is used for this purpose.
*) During compilation, both 32-bit and 64-bit vdso images are compiled and are
converted into raw bytes by vdso2c program to be ready for mapping into the
process. 32-bit images are compiled only if CONFIG_COMPAT is enabled. vdso2c
generates two files vdso-image-64.c and vdso-image-32.c which contains the
respective vDSO image in C structure.
*) During vdso initialization, required number of vdso pages are allocated and
raw bytes are copied into the pages.
*) During every exec, these pages are mapped into the process through
arch_setup_additional_pages and the location of mapping is passed on to the
process through aux vector AT_SYSINFO_EHDR which is used by glibc.
*) A new update_vsyscall routine for sparc is added to keep the data page in
vdso updated.
*) As vDSO cannot contain dynamically relocatable references, a new version of
cpu_relax is added for the use of vDSO.
This change also requires a putback to glibc to use vDSO. For testing,
programs planning to try vDSO can be compiled against the generated
vdso(64/32).so in the source.
Testing:
========
[root@localhost ~]# cat vdso_test.c
int main() {
struct timespec tv_start, tv_end;
struct timeval tv_tmp;
int i;
int count = 1 * 1000 * 10000;
long long diff;
clock_gettime(0, &tv_start);
for (i = 0; i < count; i++)
gettimeofday(&tv_tmp, NULL);
clock_gettime(0, &tv_end);
diff = (long long)(tv_end.tv_sec -
tv_start.tv_sec)*(1*1000*1000*1000);
diff += (tv_end.tv_nsec - tv_start.tv_nsec);
printf("Start sec: %d\n", tv_start.tv_sec);
printf("End sec : %d\n", tv_end.tv_sec);
printf("%d cycles in %lld ns = %f ns/cycle\n", count, diff,
(double)diff / (double)count);
return 0;
}
[root@localhost ~]# cc vdso_test.c -o t32_without_fix -m32 -lrt
[root@localhost ~]# ./t32_without_fix
Start sec: 1502396130
End sec : 1502396140
10000000 cycles in 9565148528 ns = 956.514853 ns/cycle
[root@localhost ~]# cc vdso_test.c -o t32_with_fix -m32 ./vdso32.so.dbg
[root@localhost ~]# ./t32_with_fix
Start sec: 1502396168
End sec : 1502396169
10000000 cycles in 798141262 ns = 79.814126 ns/cycle
[root@localhost ~]# cc vdso_test.c -o t64_without_fix -m64 -lrt
[root@localhost ~]# ./t64_without_fix
Start sec: 1502396208
End sec : 1502396218
10000000 cycles in 9846091800 ns = 984.609180 ns/cycle
[root@localhost ~]# cc vdso_test.c -o t64_with_fix -m64 ./vdso64.so.dbg
[root@localhost ~]# ./t64_with_fix
Start sec: 1502396257
End sec : 1502396257
10000000 cycles in 380984048 ns = 38.098405 ns/cycle
V1 to V2 Changes:
=================
Added hot patching code to switch the read stick instruction to read
tick instruction based on the hardware.
V2 to V3 Changes:
=================
Merged latest changes from sparc-next and moved the initialization
of clocksource_tick.archdata.vclock_mode to time_init_early. Disabled
queued spinlock and rwlock configuration when simulating 32-bit config
to compile 32-bit VDSO.
V3 to V4 Changes:
=================
Hardcoded the page size as 8192 in linker script for both 64-bit and
32-bit binaries. Removed unused variables in vdso2c.h. Added -mv8plus flag to
Makefile to prevent the generation of relocation entries for __lshrdi3 in 32-bit
vdso binary.
Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Signed-off-by: Nagarathnam Muthusamy <nagarathnam.muthusamy@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
David S. Miller