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selftest/vm: verify mmap addr in mremap_test
Avoid calling mmap with requested addresses that are less than the system's mmap_min_addr. When run as root, mmap returns EACCES when trying to map addresses < mmap_min_addr. This is not one of the error codes for the condition to retry the mmap in the test. Rather than arbitrarily retrying on EACCES, don't attempt an mmap until addr > vm.mmap_min_addr. Add a munmap call after an alignment check as the mappings are retained after the retry and can reach the vm.max_map_count sysctl. Link: https://lkml.kernel.org/r/20220420215721.4868-1-sidhartha.kumar@oracle.com Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com> Reviewed-by: Shuah Khan <skhan@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -6,6 +6,7 @@
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#include <errno.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <time.h>
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@ -63,6 +64,35 @@ enum {
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.expect_failure = should_fail \
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}
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/* Returns mmap_min_addr sysctl tunable from procfs */
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static unsigned long long get_mmap_min_addr(void)
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{
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FILE *fp;
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int n_matched;
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static unsigned long long addr;
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if (addr)
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return addr;
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fp = fopen("/proc/sys/vm/mmap_min_addr", "r");
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if (fp == NULL) {
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ksft_print_msg("Failed to open /proc/sys/vm/mmap_min_addr: %s\n",
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strerror(errno));
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exit(KSFT_SKIP);
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}
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n_matched = fscanf(fp, "%llu", &addr);
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if (n_matched != 1) {
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ksft_print_msg("Failed to read /proc/sys/vm/mmap_min_addr: %s\n",
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strerror(errno));
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fclose(fp);
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exit(KSFT_SKIP);
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}
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fclose(fp);
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return addr;
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}
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/*
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* Returns the start address of the mapping on success, else returns
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* NULL on failure.
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@ -71,8 +101,15 @@ static void *get_source_mapping(struct config c)
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{
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unsigned long long addr = 0ULL;
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void *src_addr = NULL;
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unsigned long long mmap_min_addr;
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mmap_min_addr = get_mmap_min_addr();
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retry:
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addr += c.src_alignment;
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if (addr < mmap_min_addr)
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goto retry;
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src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
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MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
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-1, 0);
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@ -90,8 +127,10 @@ retry:
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* alignment in the tests.
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*/
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if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
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!((unsigned long long) src_addr & c.src_alignment))
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!((unsigned long long) src_addr & c.src_alignment)) {
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munmap(src_addr, c.region_size);
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goto retry;
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}
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if (!src_addr)
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goto error;
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