Re: [PATCH] radeon: Do not directly dereference pointers to BIOS area.

From: Christian König
Date: Thu Mar 19 2015 - 05:26:05 EST


In general I would say yes, but for this particular hardware it's a bit questionable to do so.

For radeon hardware to work correctly the CPU access to the PCIE BARs should work even without using the specialized IO macros/functions, otherwise mapping VRAM CPU accessible isn't really possible.

What's the background of the change? Some problems on a certain CPU platform? or just general cleanups?

Regards,
Christian.

On 19.03.2015 04:18, David Miller wrote:
Use readb() and memcpy_fromio() accessors instead.

Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>

diff --git a/drivers/gpu/drm/radeon/radeon_bios.c b/drivers/gpu/drm/radeon/radeon_bios.c
index 63ccb8f..d27e4cc 100644
--- a/drivers/gpu/drm/radeon/radeon_bios.c
+++ b/drivers/gpu/drm/radeon/radeon_bios.c
@@ -76,7 +76,7 @@ static bool igp_read_bios_from_vram(struct radeon_device *rdev)
static bool radeon_read_bios(struct radeon_device *rdev)
{
- uint8_t __iomem *bios;
+ uint8_t __iomem *bios, val1, val2;
size_t size;
rdev->bios = NULL;
@@ -86,15 +86,19 @@ static bool radeon_read_bios(struct radeon_device *rdev)
return false;
}
- if (size == 0 || bios[0] != 0x55 || bios[1] != 0xaa) {
+ val1 = readb(&bios[0]);
+ val2 = readb(&bios[1]);
+
+ if (size == 0 || val1 != 0x55 || val2 != 0xaa) {
pci_unmap_rom(rdev->pdev, bios);
return false;
}
- rdev->bios = kmemdup(bios, size, GFP_KERNEL);
+ rdev->bios = kzalloc(size, GFP_KERNEL);
if (rdev->bios == NULL) {
pci_unmap_rom(rdev->pdev, bios);
return false;
}
+ memcpy_fromio(rdev->bios, bios, size);
pci_unmap_rom(rdev->pdev, bios);
return true;
}

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