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| author | Helge Deller <deller@gmx.de> | 2022-10-14 10:18:53 +0200 |
|---|---|---|
| committer | Helge Deller <deller@gmx.de> | 2022-10-14 10:45:12 +0200 |
| commit | 70be49f2f6223ddd2fcddb0089a40864c37e1494 (patch) | |
| tree | b81243ea631703443dac1ebc2763bb1befa79d8f /arch/parisc/kernel | |
| parent | parisc: fbdev/stifb: Align graphics memory size to 4MB (diff) | |
| download | linux-70be49f2f6223ddd2fcddb0089a40864c37e1494.tar.xz linux-70be49f2f6223ddd2fcddb0089a40864c37e1494.zip | |
parisc: Fix userspace graphics card breakage due to pgtable special bit
Commit df24e1783e6e ("parisc: Add vDSO support") introduced the vDSO
support, for which a _PAGE_SPECIAL page table flag was needed. Since we
wanted to keep every page table entry in 32-bits, this patch re-used the
existing - but yet unused - _PAGE_DMB flag (which triggers a hardware break
if a page is accessed) to store the special bit.
But when graphics card memory is mmapped into userspace, the kernel uses
vm_iomap_memory() which sets the the special flag. So, with the DMB bit
set, every access to the graphics memory now triggered a hardware
exception and segfaulted the userspace program.
Fix this breakage by dropping the DMB bit when writing the page
protection bits to the CPU TLB.
In addition this patch adds a small optimization: if huge pages aren't
configured (which is at least the case for 32-bit kernels), then the
special bit is stored in the hpage (HUGE PAGE) bit instead. That way we
can skip to reset the DMB bit.
Fixes: df24e1783e6e ("parisc: Add vDSO support")
Cc: <stable@vger.kernel.org> # 5.18+
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to '')
| -rw-r--r-- | arch/parisc/kernel/entry.S | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index df8102fb435f..0e5ebfe8d9d2 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -499,6 +499,10 @@ * Finally, _PAGE_READ goes in the top bit of PL1 (so we * trigger an access rights trap in user space if the user * tries to read an unreadable page */ +#if _PAGE_SPECIAL_BIT == _PAGE_DMB_BIT + /* need to drop DMB bit, as it's used as SPECIAL flag */ + depi 0,_PAGE_SPECIAL_BIT,1,\pte +#endif depd \pte,8,7,\prot /* PAGE_USER indicates the page can be read with user privileges, @@ -529,6 +533,10 @@ * makes the tlb entry for the differently formatted pa11 * insertion instructions */ .macro make_insert_tlb_11 spc,pte,prot +#if _PAGE_SPECIAL_BIT == _PAGE_DMB_BIT + /* need to drop DMB bit, as it's used as SPECIAL flag */ + depi 0,_PAGE_SPECIAL_BIT,1,\pte +#endif zdep \spc,30,15,\prot dep \pte,8,7,\prot extru,= \pte,_PAGE_NO_CACHE_BIT,1,%r0 |