Both the vdso rework and the CONFIG_PAGE_SHIFT changes were merged during
the v6.9 merge window, so it is now possible to use CONFIG_PAGE_SHIFT
instead of including asm/page.h in the vdso.
This avoids the workaround for arm64 - commit 8b3843ae36 ("vdso/datapage:
Quick fix - use asm/page-def.h for ARM64") and addresses a build warning
for powerpc64:
In file included from <built-in>:4:
In file included from /home/arnd/arm-soc/arm-soc/lib/vdso/gettimeofday.c:5:
In file included from ../include/vdso/datapage.h:25:
arch/powerpc/include/asm/page.h:230:9: error: result of comparison of constant 13835058055282163712 with expression of type 'unsigned long' is always true [-Werror,-Wtautological-constant-out-of-range-compare]
230 | return __pa(kaddr) >> PAGE_SHIFT;
| ^~~~~~~~~~~
arch/powerpc/include/asm/page.h:217:37: note: expanded from macro '__pa'
217 | VIRTUAL_WARN_ON((unsigned long)(x) < PAGE_OFFSET); \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
arch/powerpc/include/asm/page.h:202:73: note: expanded from macro 'VIRTUAL_WARN_ON'
202 | #define VIRTUAL_WARN_ON(x) WARN_ON(IS_ENABLED(CONFIG_DEBUG_VIRTUAL) && (x))
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
arch/powerpc/include/asm/bug.h:88:25: note: expanded from macro 'WARN_ON'
88 | int __ret_warn_on = !!(x); \
| ^
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Link: https://lore.kernel.org/r/20240320180228.136371-1-arnd@kernel.org
Prepare for switching VDSO to generic C implementation in following
patch. Here, we:
- Prepare the helpers to call the C VDSO functions
- Prepare the required callbacks for the C VDSO functions
- Prepare the clocksource.h files to define VDSO_ARCH_CLOCKMODES
- Add the C trampolines to the generic C VDSO functions
powerpc is a bit special for VDSO as well as system calls in the
way that it requires setting CR SO bit which cannot be done in C.
Therefore, entry/exit needs to be performed in ASM.
Implementing __arch_get_vdso_data() would clobber the link register,
requiring the caller to save it. As the ASM calling function already
has to set a stack frame and saves the link register before calling
the C vdso function, retriving the vdso data pointer there is lighter.
Implement __arch_vdso_capable() and always return true.
Provide vdso_shift_ns(), as the generic x >> s gives the following
bad result:
18: 35 25 ff e0 addic. r9,r5,-32
1c: 41 80 00 10 blt 2c <shift+0x14>
20: 7c 64 4c 30 srw r4,r3,r9
24: 38 60 00 00 li r3,0
...
2c: 54 69 08 3c rlwinm r9,r3,1,0,30
30: 21 45 00 1f subfic r10,r5,31
34: 7c 84 2c 30 srw r4,r4,r5
38: 7d 29 50 30 slw r9,r9,r10
3c: 7c 63 2c 30 srw r3,r3,r5
40: 7d 24 23 78 or r4,r9,r4
In our case the shift is always <= 32. In addition, the upper 32 bits
of the result are likely nul. Lets GCC know it, it also optimises the
following calculations.
With the patch, we get:
0: 21 25 00 20 subfic r9,r5,32
4: 7c 69 48 30 slw r9,r3,r9
8: 7c 84 2c 30 srw r4,r4,r5
c: 7d 24 23 78 or r4,r9,r4
10: 7c 63 2c 30 srw r3,r3,r5
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126131006.2431205-6-mpe@ellerman.id.au
