intel: Replace zero-length array with flexible-array member
Subsystems (3)
PATCH 1/1 intel: Replace zero-length array with flexible-array member
The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99:
struct foo {
int stuff;
struct boo array[];
};By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this change:
"Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
--- drivers/net/ethernet/intel/fm10k/fm10k.h | 6 +++--- drivers/net/ethernet/intel/i40e/i40e.h | 4 ++-- drivers/net/ethernet/intel/igb/igb.h | 2 +- drivers/net/ethernet/intel/igc/igc.h | 2 +- drivers/net/ethernet/intel/ixgbe/ixgbe.h | 2 +- 5 files changed, 8 insertions(+), 8 deletions(-)
drivers/net/ethernet/intel/fm10k/fm10k.h +3 -3
@@ -41,7 +41,7 @@ struct fm10k_l2_accel {u16 count;u16 dglort;struct rcu_head rcu; -struct net_device *macvlan[0 ]; +struct net_device *macvlan[]; };enum fm10k_ring_state_t {
@@ -198,7 +198,7 @@ struct fm10k_q_vector {struct rcu_head rcu;/* to avoid race with update stats on free */ /* for dynamic allocation of rings associated with this q_vector */ -struct fm10k_ring ring[0 ]____cacheline_internodealigned_in_smp ; +struct fm10k_ring ring[]____cacheline_internodealigned_in_smp ; };enum fm10k_ring_f_enum {
@@ -218,7 +218,7 @@ struct fm10k_iov_data {unsigned int num_vfs;unsigned int next_vf_mbx;struct rcu_head rcu; -struct fm10k_vf_info vf_info[0 ]; +struct fm10k_vf_info vf_info[]; };struct fm10k_udp_port {
drivers/net/ethernet/intel/i40e/i40e.h +2 -2
@@ -334,13 +334,13 @@ int i40e_ddp_flash(struct net_device *netdev, struct ethtool_flash *flash);struct i40e_ddp_profile_list {u32 p_count; -struct i40e_profile_info p_info[0 ]; +struct i40e_profile_info p_info[]; };struct i40e_ddp_old_profile_list {struct list_head list;size_t old_ddp_size; -u8 old_ddp_buf[0 ]; +u8 old_ddp_buf[]; };/* macros related to FLX_PIT */
drivers/net/ethernet/intel/igb/igb.h +1 -1
@@ -306,7 +306,7 @@ struct igb_q_vector {char name[IFNAMSIZ +9 ];/* for dynamic allocation of rings associated with this q_vector */ -struct igb_ring ring[0 ]____cacheline_internodealigned_in_smp ; +struct igb_ring ring[]____cacheline_internodealigned_in_smp ; };enum e1000_ring_flags_t {
drivers/net/ethernet/intel/igc/igc.h +1 -1
@@ -326,7 +326,7 @@ struct igc_q_vector {struct net_device poll_dev;/* for dynamic allocation of rings associated with this q_vector */ -struct igc_ring ring[0 ]____cacheline_internodealigned_in_smp ; +struct igc_ring ring[]____cacheline_internodealigned_in_smp ; };#define MAX_ETYPE_FILTER (4 - 1)
drivers/net/ethernet/intel/ixgbe/ixgbe.h +1 -1
@@ -462,7 +462,7 @@ struct ixgbe_q_vector {char name[IFNAMSIZ +9 ];/* for dynamic allocation of rings associated with this q_vector */ -struct ixgbe_ring ring[0 ]____cacheline_internodealigned_in_smp ; +struct ixgbe_ring ring[]____cacheline_internodealigned_in_smp ; };#ifdef CONFIG_IXGBE_HWMON
Signature · 1 line
2.25.0
From: "Gustavo A. R. Silva" <[email protected]>
Date: Mon, 24 Feb 2020 10:41:06 -0600
Quoted 22 lines
The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99:
struct foo { int stuff; struct boo array[]; };By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this change:
"Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1]
Quoted 7 lines
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit76497732932f("cxgb3/l2t: Fix undefined behaviour")Signed-off-by Gustavo A. R. Silva <[email protected]>
Applied.