* Re: [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space
2020-10-01 14:56 [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space Gustavo A. R. Silva
@ 2020-10-01 15:39 ` Joe Perches
2020-10-01 16:59 ` [tip: x86/platform] x86/uv/time: Use a flexible array in struct uv_rtc_timer_head tip-bot2 for Gustavo A. R. Silva
2020-10-01 17:42 ` [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space Steve Wahl
2 siblings, 0 replies; 4+ messages in thread
From: Joe Perches @ 2020-10-01 15:39 UTC (permalink / raw)
To: Gustavo A. R. Silva, Steve Wahl, Dimitri Sivanich, Russ Anderson,
Darren Hart, Andy Shevchenko, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, H. Peter Anvin
Cc: x86, platform-driver-x86, linux-kernel, Kees Cook, linux-hardening
On Thu, 2020-10-01 at 09:56 -0500, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> struct uv_rtc_timer_head contains a one-element array cpu[1].
>
> Switch it to a flexible array and use the struct_size() helper to
> calculate the allocation size. Also, save some heap space in the
> process[3].
trivia:
> diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
[]
> @@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void)
> struct uv_rtc_timer_head *head = blade_info[bid];
>
> if (!head) {
> - head = kmalloc_node(sizeof(struct uv_rtc_timer_head) +
> - (uv_blade_nr_possible_cpus(bid) *
> - 2 * sizeof(u64)),
> + head = kmalloc_node(struct_size(head, cpu,
> + uv_blade_nr_possible_cpus(bid)),
> GFP_KERNEL, nid);
> if (!head) {
> uv_rtc_deallocate_timers();
Maybe save the value of uv_blade_nr_possible_cpus(bid)
to reduce duplication and make the sizeof_struct more
readable?
if (!head) {
int ncpus = uv_blade_nr_possible_cpus(bid);
head = kmalloc_node(struct_size(head, cpu, ncpus),
GFP_KERNEL, nid);
if (!head) {
uv_rtc_deallocate_timers();
return -ENOMEM;
}
spin_lock_init(&head->lock);
head->ncpus = ncpus;
head->next_cpu = -1;
blade_info[bid] = head;
}
^ permalink raw reply [flat|nested] 4+ messages in thread* [tip: x86/platform] x86/uv/time: Use a flexible array in struct uv_rtc_timer_head
2020-10-01 14:56 [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space Gustavo A. R. Silva
2020-10-01 15:39 ` Joe Perches
@ 2020-10-01 16:59 ` tip-bot2 for Gustavo A. R. Silva
2020-10-01 17:42 ` [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space Steve Wahl
2 siblings, 0 replies; 4+ messages in thread
From: tip-bot2 for Gustavo A. R. Silva @ 2020-10-01 16:59 UTC (permalink / raw)
To: linux-tip-commits
Cc: Gustavo A. R. Silva, Borislav Petkov, Kees Cook, Steve Wahl, x86, LKML
The following commit has been merged into the x86/platform branch of tip:
Commit-ID: a0947081af2ac9549e6ba19877456730713bde23
Gitweb: https://git.kernel.org/tip/a0947081af2ac9549e6ba19877456730713bde23
Author: Gustavo A. R. Silva <gustavoars@kernel.org>
AuthorDate: Thu, 01 Oct 2020 09:56:08 -05:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Thu, 01 Oct 2020 18:47:39 +02:00
x86/uv/time: Use a flexible array in struct uv_rtc_timer_head
There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The
older style of one-element or zero-length arrays should no longer be
used[2].
struct uv_rtc_timer_head contains a one-element array cpu[1]. Switch it
to a flexible array and use the struct_size() helper to calculate the
allocation size. Also, save some heap space in the process[3].
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
[3] https://lore.kernel.org/lkml/20200518190114.GA7757@embeddedor/
[ bp: Massage a bit. ]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Steve Wahl <steve.wahl@hpe.com>
Link: https://lkml.kernel.org/r/20201001145608.GA10204@embeddedor
---
arch/x86/platform/uv/uv_time.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
index f82a133..6c348c2 100644
--- a/arch/x86/platform/uv/uv_time.c
+++ b/arch/x86/platform/uv/uv_time.c
@@ -52,7 +52,7 @@ struct uv_rtc_timer_head {
struct {
int lcpu; /* systemwide logical cpu number */
u64 expires; /* next timer expiration for this cpu */
- } cpu[1];
+ } cpu[];
};
/*
@@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void)
struct uv_rtc_timer_head *head = blade_info[bid];
if (!head) {
- head = kmalloc_node(sizeof(struct uv_rtc_timer_head) +
- (uv_blade_nr_possible_cpus(bid) *
- 2 * sizeof(u64)),
+ head = kmalloc_node(struct_size(head, cpu,
+ uv_blade_nr_possible_cpus(bid)),
GFP_KERNEL, nid);
if (!head) {
uv_rtc_deallocate_timers();
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space
2020-10-01 14:56 [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space Gustavo A. R. Silva
2020-10-01 15:39 ` Joe Perches
2020-10-01 16:59 ` [tip: x86/platform] x86/uv/time: Use a flexible array in struct uv_rtc_timer_head tip-bot2 for Gustavo A. R. Silva
@ 2020-10-01 17:42 ` Steve Wahl
2 siblings, 0 replies; 4+ messages in thread
From: Steve Wahl @ 2020-10-01 17:42 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: Steve Wahl, Dimitri Sivanich, Russ Anderson, Darren Hart,
Andy Shevchenko, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
H. Peter Anvin, x86, platform-driver-x86, linux-kernel,
Kees Cook, linux-hardening
On Thu, Oct 01, 2020 at 09:56:08AM -0500, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
I see this has already gone in, so I'm late. But for whatever it's
worth, it's a good change. Thank you.
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
--> Steve wahl
> struct uv_rtc_timer_head contains a one-element array cpu[1].
>
> Switch it to a flexible array and use the struct_size() helper to
> calculate the allocation size. Also, save some heap space in the
> process[3].
>
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays
> [3] https://lore.kernel.org/lkml/20200518190114.GA7757@embeddedor/
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Build-tested-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/lkml/5f75bc0a.rQcNS6620b2eA74S%25lkp@intel.com/
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes in v2:
> - Modify changelog text (Thomas).
> - Add Reviewed-by and Build-tested-by tags.
> - Add a public link to the build-test results.
>
> arch/x86/platform/uv/uv_time.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
> index f82a1337a608..6c348c2d0def 100644
> --- a/arch/x86/platform/uv/uv_time.c
> +++ b/arch/x86/platform/uv/uv_time.c
> @@ -52,7 +52,7 @@ struct uv_rtc_timer_head {
> struct {
> int lcpu; /* systemwide logical cpu number */
> u64 expires; /* next timer expiration for this cpu */
> - } cpu[1];
> + } cpu[];
> };
>
> /*
> @@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void)
> struct uv_rtc_timer_head *head = blade_info[bid];
>
> if (!head) {
> - head = kmalloc_node(sizeof(struct uv_rtc_timer_head) +
> - (uv_blade_nr_possible_cpus(bid) *
> - 2 * sizeof(u64)),
> + head = kmalloc_node(struct_size(head, cpu,
> + uv_blade_nr_possible_cpus(bid)),
> GFP_KERNEL, nid);
> if (!head) {
> uv_rtc_deallocate_timers();
> --
> 2.27.0
>
^ permalink raw reply [flat|nested] 4+ messages in thread