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Date: Mon, 14 Jan 2013 18:47:06 +0000
From: Cong Ding <dinggnu@...il.com>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Jes Sorensen <jes@....com>, Tony Luck <tony.luck@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>, linux-altix@....com,
linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ia64: sn/pci/pcibr/pcibr_reg.c: check null pointer
dereference
On Mon, Jan 14, 2013 at 11:19:15AM -0700, Bjorn Helgaas wrote:
> On Mon, Jan 14, 2013 at 10:53 AM, Cong Ding <dinggnu@...il.com> wrote:
> > we should ensure the pointer is not null before the first use, rather than
> > after it.
>
> These changes look technically correct, but the whole pcibr_reg.c file
> is ridiculously defensive programming.
>
> For example, the first two hunks are for pcireg_control_bit_clr() and
> pcireg_control_bit_set(). These functions are called only from
> pcibr_bus_fixup(), and it's impossible for it to pass a null pointer.
> It would be better to just remove the null pointer checks completely.
>
> The panics in pcibr_reg.c are dubious, too. That sort of check
> belongs higher up, e.g., in pcibr_bus_fixup() where we set up
> pcibus_info->pbi_buscommon.bs_base in the first place.
>
Thanks Bjorn, so do you think a patch like the following would be better?
- cong
>From 5c4798565320b2eeda23b68fdf950322f4ea66ff Mon Sep 17 00:00:00 2001
From: Cong Ding <dinggnu@...il.com>
Date: Mon, 14 Jan 2013 18:41:24 +0000
Subject: [PATCH] ia64: sn/pci/pcibr/pcibr_reg.c: remove unnecessary null pointer check
These functions are called only from pcibr_bus_fixup(), and it's impossible
for it to pass a null pointer. And these pointers are used before the checks.
Signed-off-by: Cong Ding <dinggnu@...il.com>
---
arch/ia64/sn/pci/pcibr/pcibr_reg.c | 271 ++++++++++++++++--------------------
1 files changed, 120 insertions(+), 151 deletions(-)
diff --git a/arch/ia64/sn/pci/pcibr/pcibr_reg.c b/arch/ia64/sn/pci/pcibr/pcibr_reg.c
index 8b8bbd5..ae16be3c 100644
--- a/arch/ia64/sn/pci/pcibr/pcibr_reg.c
+++ b/arch/ia64/sn/pci/pcibr/pcibr_reg.c
@@ -27,19 +27,16 @@ void pcireg_control_bit_clr(struct pcibus_info *pcibus_info, u64 bits)
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- __sn_clrq_relaxed(&ptr->tio.cp_control, bits);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- __sn_clrq_relaxed(&ptr->pic.p_wid_control, bits);
- break;
- default:
- panic
- ("pcireg_control_bit_clr: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ __sn_clrq_relaxed(&ptr->tio.cp_control, bits);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ __sn_clrq_relaxed(&ptr->pic.p_wid_control, bits);
+ break;
+ default:
+ panic("pcireg_control_bit_clr: unknown bridgetype bridge 0x%p",
+ ptr);
}
}
@@ -47,19 +44,16 @@ void pcireg_control_bit_set(struct pcibus_info *pcibus_info, u64 bits)
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- __sn_setq_relaxed(&ptr->tio.cp_control, bits);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- __sn_setq_relaxed(&ptr->pic.p_wid_control, bits);
- break;
- default:
- panic
- ("pcireg_control_bit_set: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ __sn_setq_relaxed(&ptr->tio.cp_control, bits);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ __sn_setq_relaxed(&ptr->pic.p_wid_control, bits);
+ break;
+ default:
+ panic("pcireg_control_bit_set: unknown bridgetype bridge 0x%p",
+ ptr);
}
}
@@ -71,19 +65,16 @@ u64 pcireg_tflush_get(struct pcibus_info *pcibus_info)
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
u64 ret = 0;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- ret = __sn_readq_relaxed(&ptr->tio.cp_tflush);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- ret = __sn_readq_relaxed(&ptr->pic.p_wid_tflush);
- break;
- default:
- panic
- ("pcireg_tflush_get: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ ret = __sn_readq_relaxed(&ptr->tio.cp_tflush);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ ret = __sn_readq_relaxed(&ptr->pic.p_wid_tflush);
+ break;
+ default:
+ panic("pcireg_tflush_get: unknown bridgetype bridge 0x%p",
+ ptr);
}
/* Read of the Target Flush should always return zero */
@@ -96,24 +87,21 @@ u64 pcireg_tflush_get(struct pcibus_info *pcibus_info)
/*
* Interrupt Status Register Access -- Read Only 0000_0100
*/
-u64 pcireg_intr_status_get(struct pcibus_info * pcibus_info)
+u64 pcireg_intr_status_get(struct pcibus_info *pcibus_info)
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
u64 ret = 0;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- ret = __sn_readq_relaxed(&ptr->tio.cp_int_status);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- ret = __sn_readq_relaxed(&ptr->pic.p_int_status);
- break;
- default:
- panic
- ("pcireg_intr_status_get: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ ret = __sn_readq_relaxed(&ptr->tio.cp_int_status);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ ret = __sn_readq_relaxed(&ptr->pic.p_int_status);
+ break;
+ default:
+ panic("pcireg_intr_status_get: unknown bridgetype bridge 0x%p",
+ ptr);
}
return ret;
}
@@ -125,19 +113,16 @@ void pcireg_intr_enable_bit_clr(struct pcibus_info *pcibus_info, u64 bits)
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- __sn_clrq_relaxed(&ptr->tio.cp_int_enable, bits);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- __sn_clrq_relaxed(&ptr->pic.p_int_enable, bits);
- break;
- default:
- panic
- ("pcireg_intr_enable_bit_clr: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ __sn_clrq_relaxed(&ptr->tio.cp_int_enable, bits);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ __sn_clrq_relaxed(&ptr->pic.p_int_enable, bits);
+ break;
+ default:
+ panic("pcireg_intr_enable_bit_clr: unknown bridgetype bridge 0x%p",
+ ptr);
}
}
@@ -145,19 +130,16 @@ void pcireg_intr_enable_bit_set(struct pcibus_info *pcibus_info, u64 bits)
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- __sn_setq_relaxed(&ptr->tio.cp_int_enable, bits);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- __sn_setq_relaxed(&ptr->pic.p_int_enable, bits);
- break;
- default:
- panic
- ("pcireg_intr_enable_bit_set: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ __sn_setq_relaxed(&ptr->tio.cp_int_enable, bits);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ __sn_setq_relaxed(&ptr->pic.p_int_enable, bits);
+ break;
+ default:
+ panic("pcireg_intr_enable_bit_set: unknown bridgetype bridge 0x%p",
+ ptr);
}
}
@@ -169,25 +151,22 @@ void pcireg_intr_addr_addr_set(struct pcibus_info *pcibus_info, int int_n,
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- __sn_clrq_relaxed(&ptr->tio.cp_int_addr[int_n],
- TIOCP_HOST_INTR_ADDR);
- __sn_setq_relaxed(&ptr->tio.cp_int_addr[int_n],
- (addr & TIOCP_HOST_INTR_ADDR));
- break;
- case PCIBR_BRIDGETYPE_PIC:
- __sn_clrq_relaxed(&ptr->pic.p_int_addr[int_n],
- PIC_HOST_INTR_ADDR);
- __sn_setq_relaxed(&ptr->pic.p_int_addr[int_n],
- (addr & PIC_HOST_INTR_ADDR));
- break;
- default:
- panic
- ("pcireg_intr_addr_addr_get: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ __sn_clrq_relaxed(&ptr->tio.cp_int_addr[int_n],
+ TIOCP_HOST_INTR_ADDR);
+ __sn_setq_relaxed(&ptr->tio.cp_int_addr[int_n],
+ (addr & TIOCP_HOST_INTR_ADDR));
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ __sn_clrq_relaxed(&ptr->pic.p_int_addr[int_n],
+ PIC_HOST_INTR_ADDR);
+ __sn_setq_relaxed(&ptr->pic.p_int_addr[int_n],
+ (addr & PIC_HOST_INTR_ADDR));
+ break;
+ default:
+ panic("pcireg_intr_addr_addr_get: unknown bridgetype bridge 0x%p",
+ ptr);
}
}
@@ -198,19 +177,16 @@ void pcireg_force_intr_set(struct pcibus_info *pcibus_info, int int_n)
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- writeq(1, &ptr->tio.cp_force_pin[int_n]);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- writeq(1, &ptr->pic.p_force_pin[int_n]);
- break;
- default:
- panic
- ("pcireg_force_intr_set: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ writeq(1, &ptr->tio.cp_force_pin[int_n]);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ writeq(1, &ptr->pic.p_force_pin[int_n]);
+ break;
+ default:
+ panic("pcireg_force_intr_set: unknown bridgetype bridge 0x%p",
+ ptr);
}
}
@@ -222,21 +198,20 @@ u64 pcireg_wrb_flush_get(struct pcibus_info *pcibus_info, int device)
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
u64 ret = 0;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- ret =
- __sn_readq_relaxed(&ptr->tio.cp_wr_req_buf[device]);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- ret =
- __sn_readq_relaxed(&ptr->pic.p_wr_req_buf[device]);
- break;
- default:
- panic("pcireg_wrb_flush_get: unknown bridgetype bridge 0x%p", ptr);
- }
-
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ ret =
+ __sn_readq_relaxed(&ptr->tio.cp_wr_req_buf[device]);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ ret =
+ __sn_readq_relaxed(&ptr->pic.p_wr_req_buf[device]);
+ break;
+ default:
+ panic("pcireg_wrb_flush_get: unknown bridgetype bridge 0x%p",
+ ptr);
}
+
/* Read of the Write Buffer Flush should always return zero */
return ret;
}
@@ -246,19 +221,16 @@ void pcireg_int_ate_set(struct pcibus_info *pcibus_info, int ate_index,
{
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- writeq(val, &ptr->tio.cp_int_ate_ram[ate_index]);
- break;
- case PCIBR_BRIDGETYPE_PIC:
- writeq(val, &ptr->pic.p_int_ate_ram[ate_index]);
- break;
- default:
- panic
- ("pcireg_int_ate_set: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ writeq(val, &ptr->tio.cp_int_ate_ram[ate_index]);
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ writeq(val, &ptr->pic.p_int_ate_ram[ate_index]);
+ break;
+ default:
+ panic("pcireg_int_ate_set: unknown bridgetype bridge 0x%p",
+ ptr);
}
}
@@ -267,19 +239,16 @@ u64 __iomem *pcireg_int_ate_addr(struct pcibus_info *pcibus_info, int ate_index)
union br_ptr __iomem *ptr = (union br_ptr __iomem *)pcibus_info->pbi_buscommon.bs_base;
u64 __iomem *ret = NULL;
- if (pcibus_info) {
- switch (pcibus_info->pbi_bridge_type) {
- case PCIBR_BRIDGETYPE_TIOCP:
- ret = &ptr->tio.cp_int_ate_ram[ate_index];
- break;
- case PCIBR_BRIDGETYPE_PIC:
- ret = &ptr->pic.p_int_ate_ram[ate_index];
- break;
- default:
- panic
- ("pcireg_int_ate_addr: unknown bridgetype bridge 0x%p",
- ptr);
- }
+ switch (pcibus_info->pbi_bridge_type) {
+ case PCIBR_BRIDGETYPE_TIOCP:
+ ret = &ptr->tio.cp_int_ate_ram[ate_index];
+ break;
+ case PCIBR_BRIDGETYPE_PIC:
+ ret = &ptr->pic.p_int_ate_ram[ate_index];
+ break;
+ default:
+ panic("pcireg_int_ate_addr: unknown bridgetype bridge 0x%p",
+ ptr);
}
return ret;
}
--
1.7.4.5
--
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