[PATCH] PCI: brcmstb: Declare a bitmap as a bitmap, not as a plain 'unsigned long'

From: Christophe JAILLET
Date: Sun Nov 07 2021 - 03:33:25 EST


The 'used' field of 'struct brcm_msi' is used as a bitmap. So it should
be declared as so (i.e. unsigned long *).

This fixes an harmless Coverity warning about array vs singleton usage.

This bitmap can be BRCM_INT_PCI_MSI_LEGACY_NR or BRCM_INT_PCI_MSI_NR long.
So, while at it, document it, should it help someone in the future.

Addresses-Coverity: "Out-of-bounds access (ARRAY_VS_SINGLETON)"
Suggested-by: Krzysztof Wilczynski <kw@xxxxxxxxx>
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
The BUILD_BUG_ON is surely a bit to much of paranoia :)

I'm also not really pleased about the layout of the DECLARE_BITMAP. This
looks odd, but I couldn't find something nicer :(
---
drivers/pci/controller/pcie-brcmstb.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index 1fc7bd49a7ad..15d394ac7478 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -266,8 +266,9 @@ struct brcm_msi {
struct mutex lock; /* guards the alloc/free operations */
u64 target_addr;
int irq;
- /* used indicates which MSI interrupts have been alloc'd */
- unsigned long used;
+ /* Used indicates which MSI interrupts have been alloc'd. 'nr' bellow is
+ the real size of the bitmap. It depends on the chip. */
+ DECLARE_BITMAP (used, BRCM_INT_PCI_MSI_NR);
bool legacy;
/* Some chips have MSIs in bits [31..24] of a shared register. */
int legacy_shift;
@@ -534,7 +535,7 @@ static int brcm_msi_alloc(struct brcm_msi *msi)
int hwirq;

mutex_lock(&msi->lock);
- hwirq = bitmap_find_free_region(&msi->used, msi->nr, 0);
+ hwirq = bitmap_find_free_region(msi->used, msi->nr, 0);
mutex_unlock(&msi->lock);

return hwirq;
@@ -543,7 +544,7 @@ static int brcm_msi_alloc(struct brcm_msi *msi)
static void brcm_msi_free(struct brcm_msi *msi, unsigned long hwirq)
{
mutex_lock(&msi->lock);
- bitmap_release_region(&msi->used, hwirq, 0);
+ bitmap_release_region(msi->used, hwirq, 0);
mutex_unlock(&msi->lock);
}

@@ -661,6 +662,12 @@ static int brcm_pcie_enable_msi(struct brcm_pcie *pcie)
msi->irq = irq;
msi->legacy = pcie->hw_rev < BRCM_PCIE_HW_REV_33;

+ /*
+ * Sanity check to make sure that the 'used' bitmap in struct brcm_msi
+ * is large enough.
+ */
+ BUILD_BUG_ON(BRCM_INT_PCI_MSI_LEGACY_NR > BRCM_INT_PCI_MSI_NR);
+
if (msi->legacy) {
msi->intr_base = msi->base + PCIE_INTR2_CPU_BASE;
msi->nr = BRCM_INT_PCI_MSI_LEGACY_NR;
--
2.30.2