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From 96efdf51429812ec9b09f5ddb6ff24c80719e628 Mon Sep 17 00:00:00 2001
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Message-Id: <96efdf51429812ec9b09f5ddb6ff24c80719e628.1566225007.git.aquini@redhat.com>
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In-Reply-To: <d42f467a923dfc09309acb7a83b42e3285fbd8f4.1566225007.git.aquini@redhat.com>
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References: <d42f467a923dfc09309acb7a83b42e3285fbd8f4.1566225007.git.aquini@redhat.com>
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From: David Gibson <david@gibson.dropbear.id.au>
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Date: Sun, 18 Aug 2019 16:03:21 +1000
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Subject: [RHEL7 PATCH 27/31] tests: Improve TASK_SIZE detection in
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task-size-overrun
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task-size-overrun is designed to test kernel behaviour in some edge cases
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involving making a hugepage mapping right near the address space limits.
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In order to do that, it needs to know the TASK_SIZE of the kernel it's
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running on.
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Currently it does that with a linear search from the last extant mapping.
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But with kernels supporting a very large address space that can take
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prohibitively long. We've had problems with that before, resulting in some
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hacks to skip a large chunk of address space.
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Those hacks are dependent on platform, though, which is ugly and fragile.
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Case in point, recent powerpc kernels now support a 4PiB address space,
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so the logic we have there is insufficient to finish the search in
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reasonable time.
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To handle this in a more robust way, this replaces the linear search with
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a binary search between the last extant mapping and (2^wordsize).
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Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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Signed-off-by: Eric B Munson <eric@munsonfam.org>
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Signed-off-by: Rafael Aquini <aquini@redhat.com>
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---
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tests/task-size-overrun.c | 57 +++++++++++++++++++++++------------------------
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1 file changed, 28 insertions(+), 29 deletions(-)
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diff --git a/tests/task-size-overrun.c b/tests/task-size-overrun.c
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index 914ef65..29b6045 100644
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--- a/tests/task-size-overrun.c
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+++ b/tests/task-size-overrun.c
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@@ -64,45 +64,44 @@ static unsigned long find_last_mapped(void)
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return end;
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}
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+#define ALIGN_DOWN(x,a) ((x) & ~((a) - 1))
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+
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static unsigned long find_task_size(void)
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{
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- unsigned long addr;
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+ unsigned long low, high; /* PFNs */
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void *p;
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- addr = find_last_mapped();
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- if (!addr || ((addr % getpagesize()) != 0))
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- FAIL("Bogus stack end address, 0x%lx!?", addr);
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+ low = find_last_mapped();
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+ if (!low || ((low % getpagesize()) != 0))
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+ FAIL("Bogus stack end address, 0x%lx!?", low);
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+ low = low / getpagesize();
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+
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+ /* This sum should get us (2^(wordsize) - 2 pages) */
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+ high = (unsigned long)(-2 * getpagesize()) / getpagesize();
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+
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+ verbose_printf("Binary searching for task size PFNs 0x%lx..0x%lx\n",
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+ low, high);
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+
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+ while (high > low + 1) {
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+ unsigned long pfn = (low + high) / 2;
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+ unsigned long addr = pfn * getpagesize();
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+
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+ assert((pfn >= low) && (pfn <= high));
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- while (addr) {
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p = mmap64((void *)addr, getpagesize(), PROT_READ,
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MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0);
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if (p == MAP_FAILED) {
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- verbose_printf("Searching map failed: %s\n", strerror(errno));
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- return addr;
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+ verbose_printf("Map failed at 0x%lx (%s)\n",
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+ addr, strerror(errno));
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+ high = pfn;
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+ } else {
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+ verbose_printf("Map succeeded at 0x%lx\n", addr);
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+ munmap(p, getpagesize());
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+ low = pfn;
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}
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- munmap(p, getpagesize());
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- addr += getpagesize();
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-#if defined(__powerpc64__)
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- if (addr > (1UL << 46) && addr < (1UL << 47))
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- addr = 1UL << 47; /* 64TB */
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- else if (addr > (1UL << 47) && addr < (1UL << 48))
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- addr = 1UL << 48; /* 128TB */
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- else if (addr > (1UL << 48) && addr < (1UL << 49))
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- addr = 1UL << 49; /* 512TB */
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- else if (addr > (1UL << 49) && addr < (1UL << 50))
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- addr = 1UL << 50; /* 1PB */
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- else if (addr > (1UL << 50) && addr < (1UL << 51))
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- addr = 1UL << 51; /* 2PB */
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- else if (addr > (1UL << 51) && addr < (1UL << 52))
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- addr = 1UL << 52; /* 4PB */
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-#endif
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-#if defined(__s390x__)
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- if (addr > (1UL << 42) && addr < (1UL << 53))
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- addr = 1UL << 53;
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-#endif
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}
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- /* addr wrapped around */
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- return 0;
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+
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+ return low * getpagesize();
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}
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int main(int argc, char *argv[])
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--
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1.8.3.1
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