From: Goran Ferenc goran.ferenc@imgtec.com
[ Upstream commit 8ec7f15b8cca4f790df5cdf33f26e2926d4ee2fd ]
Fix incorrect calculation in do_monotonic() and do_monotonic_coarse() function that in turn caused incorrect values returned by the vdso version of system call clock_gettime() on mips64 if its system clock ID parameter was CLOCK_MONOTONIC or CLOCK_MONOTONIC_COARSE.
Consider these variables and their types on mips32 and mips64:
tk->wall_to_monotonic.tv_sec s64, s64 (kernel/vdso.c) vdso_data.wall_to_mono_sec u32, u32 (kernel/vdso.c) to_mono_sec u32, u32 (vdso/gettimeofday.c) ts->tv_sec s32, s64 (vdso/gettimeofday.c)
For mips64 case, u32 vdso_data.wall_to_mono_sec variable is updated from the 64-bit signed variable tk->wall_to_monotonic.tv_sec (kernel/vdso.c:76) which is a negative number holding the time passed from 1970-01-01 to the time boot started. This 64-bit signed value is currently around 47+ years, in seconds. For instance, let this value be:
-1489757461
or
11111111111111111111111111111111 10100111001101000001101011101011
By updating 32-bit vdso_data.wall_to_mono_sec variable, we lose upper 32 bits (signed 1's).
to_mono_sec variable is a parameter of do_monotonic() and do_monotonic_coarse() functions which holds vdso_data.wall_to_mono_sec value. Its value needs to be added (or subtracted considering it holds negative value from the tk->wall_to_monotonic.tv_sec) to the current time passed from 1970-01-01 (ts->tv_sec), which is again something like 47+ years, but increased by the time passed from the boot to the current time. ts->tv_sec is 32-bit long in case of 32-bit architecture and 64-bit long in case of 64-bit architecture. Consider the update of ts->tv_sec (vdso/gettimeofday.c:55 & 167):
ts->tv_sec += to_mono_sec;
mips32 case: This update will be performed correctly, since both ts->tv_sec and to_mono_sec are 32-bit long and the sign in to_mono_sec is preserved. Implicit conversion from u32 to s32 will be done correctly.
mips64 case: This update will be wrong, since the implicit conversion will not be done correctly. The reason is that the conversion will be from u32 to s64. This is because to_mono_sec is 32-bit long for both mips32 and mips64 cases and s64..33 bits of converted to_mono_sec variable will be zeros.
So, in order to make MIPS64 implementation work properly for MONOTONIC and MONOTONIC_COARSE clock ids on mips64, the size of wall_to_mono_sec variable in mips_vdso_data union and respective parameters in do_monotonic() and do_monotonic_coarse() functions should be changed from u32 to u64. Because of consistency, this size change from u32 and u64 is also done for wall_to_mono_nsec variable and corresponding function parameters.
As far as similar situations for other architectures are concerned, let's take a look at arm. Arm has two distinct vdso_data structures for 32-bit & 64-bit cases, and arm's wall_to_mono_sec and wall_to_mono_nsec are u32 for 32-bit and u64 for 64-bit cases. On the other hand, MIPS has only one structure (mips_vdso_data), hence the need for changing the size of above mentioned parameters.
Signed-off-by: Goran Ferenc goran.ferenc@imgtec.com Signed-off-by: Miodrag Dinic miodrag.dinic@imgtec.com Signed-off-by: Aleksandar Markovic aleksandar.markovic@imgtec.com Cc: Douglas Leung douglas.leung@imgtec.com Cc: James Hogan james.hogan@imgtec.com Cc: Paul Burton paul.burton@imgtec.com Cc: Petar Jovanovic petar.jovanovic@imgtec.com Cc: Raghu Gandham raghu.gandham@imgtec.com Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/16638/ Signed-off-by: Ralf Baechle ralf@linux-mips.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- arch/mips/include/asm/vdso.h | 4 ++-- arch/mips/vdso/gettimeofday.c | 8 ++++---- 2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/mips/include/asm/vdso.h b/arch/mips/include/asm/vdso.h index 8f4ca5dd992b..b7cd6cf77b83 100644 --- a/arch/mips/include/asm/vdso.h +++ b/arch/mips/include/asm/vdso.h @@ -79,8 +79,8 @@ union mips_vdso_data { struct { u64 xtime_sec; u64 xtime_nsec; - u32 wall_to_mono_sec; - u32 wall_to_mono_nsec; + u64 wall_to_mono_sec; + u64 wall_to_mono_nsec; u32 seq_count; u32 cs_shift; u8 clock_mode; diff --git a/arch/mips/vdso/gettimeofday.c b/arch/mips/vdso/gettimeofday.c index ce89c9e294f9..fd7d433970bf 100644 --- a/arch/mips/vdso/gettimeofday.c +++ b/arch/mips/vdso/gettimeofday.c @@ -39,8 +39,8 @@ static __always_inline int do_monotonic_coarse(struct timespec *ts, const union mips_vdso_data *data) { u32 start_seq; - u32 to_mono_sec; - u32 to_mono_nsec; + u64 to_mono_sec; + u64 to_mono_nsec;
do { start_seq = vdso_data_read_begin(data); @@ -148,8 +148,8 @@ static __always_inline int do_monotonic(struct timespec *ts, { u32 start_seq; u64 ns; - u32 to_mono_sec; - u32 to_mono_nsec; + u64 to_mono_sec; + u64 to_mono_nsec;
do { start_seq = vdso_data_read_begin(data);