From 8ec4c5dae32765701ac70811455084efd1570c32 Mon Sep 17 00:00:00 2001 From: Ed Maste Date: Sun, 21 Nov 2021 12:17:20 -0500 Subject: [PATCH] Fix coredump_phnum test with ASLR enabled by default coredump_phnum intends to generate a core file with many PT_LOAD segments. Previously it called mmap() in a loop with alternating protections, relying on each mapping following the previous, to produce a core file with many page-sized PT_LOAD segments. With ASLR on we no longer have this property of each mmap() following the previous. Instead, perform a single allocation, and then use mprotect() to set alternating pages to PROT_READ. PR: 259970 Reported by: lwhsu, mw Reviewed by: kib MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D33070 --- tests/sys/kern/coredump_phnum_helper.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/tests/sys/kern/coredump_phnum_helper.c b/tests/sys/kern/coredump_phnum_helper.c index da023e691a2..0dff59b918d 100644 --- a/tests/sys/kern/coredump_phnum_helper.c +++ b/tests/sys/kern/coredump_phnum_helper.c @@ -42,18 +42,21 @@ int main(int argc __unused, char **argv __unused) { void *v; - unsigned i; + size_t i, pages; - for (i = 0; i < UINT16_MAX + 1000; i++) { + pages = UINT16_MAX + 1000; + v = mmap(NULL, pages * PAGE_SIZE, PROT_READ | PROT_WRITE, + MAP_ANON | MAP_PRIVATE, -1, 0); + if (v == NULL) + err(1, "mmap"); + for (i = 0; i < pages; i += 2) { /* - * Alternate protections; otherwise the kernel will just extend - * the adjacent same-protection previous mapping. + * Alternate protections to interleave RW and R PT_LOAD + * segments. */ - v = mmap(NULL, PAGE_SIZE, - (((i % 2) == 0) ? PROT_READ : 0) | PROT_WRITE, - MAP_ANON | MAP_PRIVATE, -1, 0); - if (v == MAP_FAILED) - err(1, "mmap"); + if (mprotect((char *)v + i * PAGE_SIZE, PAGE_SIZE, + PROT_READ) != 0) + err(1, "mprotect"); } /* Dump core. */ -- 2.45.2