diff options
| author | Peter Maydell <peter.maydell@linaro.org> | 2015-06-15 18:06:07 +0100 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2015-06-15 18:06:07 +0100 |
| commit | fc1891c74ae122a9dc7854f38bae7db03cd911e6 (patch) | |
| tree | b039e7dbedae54c639545f5a92ed6d956aa13fd6 /target-arm | |
| parent | b500e4db8e3e0b5f41a2dd14e2001200e5fc7d6b (diff) | |
target-arm: Handle "extended small page" descriptors correctly
The old ARMv5-style page table format includes a kind of second level
descriptor named the "extended small page" format, whose primary purpose
is to allow specification of the TEX memory attribute bits on a 4K page.
This exists on ARMv6 and also (as an implementation extension) on XScale
CPUs; it's UNPREDICTABLE on v5.
We were mishandling this in two ways:
(1) we weren't implementing it for v6 (probably never noticed because
Linux will use the new-style v6 page table format there)
(2) we were not correctly setting the page_size, which is 4K, not 1K
The latter bug went unnoticed for years because the only thing which
the page_size affects is which TLB entries get flushed when the guest
does a TLB invalidate on an address in the page, and prior to commit
2f0d8631b7 we were doing a full TLB flush very frequently due to Linux's
habit of writing the SCTLR pointlessly a lot.
(We can assume that after commit 2f0d8631b7 the bug went unnoticed
for a year because nobody's actually using the Zaurus/XScale emulation...)
Report the correct page size for these descriptors, and permit them
on ARMv6 CPUs. This fixes a problem where a kernel image for Zaurus
can boot the kernel OK but gets random segfaults when it tries to
run userspace programs.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1432844085-16441-1-git-send-email-peter.maydell@linaro.org
Diffstat (limited to 'target-arm')
| -rw-r--r-- | target-arm/helper.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/target-arm/helper.c b/target-arm/helper.c index 3da0c0579c..3ed2fc3fa2 100644 --- a/target-arm/helper.c +++ b/target-arm/helper.c @@ -5302,20 +5302,25 @@ static int get_phys_addr_v5(CPUARMState *env, uint32_t address, int access_type, ap = (desc >> (4 + ((address >> 9) & 6))) & 3; *page_size = 0x1000; break; - case 3: /* 1k page. */ + case 3: /* 1k page, or ARMv6/XScale "extended small (4k) page" */ if (type == 1) { - if (arm_feature(env, ARM_FEATURE_XSCALE)) { + /* ARMv6/XScale extended small page format */ + if (arm_feature(env, ARM_FEATURE_XSCALE) + || arm_feature(env, ARM_FEATURE_V6)) { phys_addr = (desc & 0xfffff000) | (address & 0xfff); + *page_size = 0x1000; } else { - /* Page translation fault. */ + /* UNPREDICTABLE in ARMv5; we choose to take a + * page translation fault. + */ code = 7; goto do_fault; } } else { phys_addr = (desc & 0xfffffc00) | (address & 0x3ff); + *page_size = 0x400; } ap = (desc >> 4) & 3; - *page_size = 0x400; break; default: /* Never happens, but compiler isn't smart enough to tell. */ |