[dpdk-dev] [PATCH v4] eal: use madvise to exclude unmapped memory from being dumped

[Li Feng]

Currently, even though memory is mapped with PROT_NONE, this does not
cause it to be excluded from core dumps. This is counter-productive,
because in a lot of cases, this memory will go unused (e.g. when the
memory subsystem preallocates VA space but hasn't yet mapped physical
pages into it).

Use `madvise()` call with MADV_DONTDUMP parameter to exclude the
unmapped memory from being dumped.

Signed-off-by: Li Feng <fen...@smartx.com>
---
V4:
- simplify the code;
- remove the undo code in V3;

V3:
- add support for freebsd.
- when free_seg is called, mark the memory MADV_DONTDUMP.
- when alloc_seg is called, mark the memory MADV_DODUMP.

 lib/librte_eal/common/eal_common_memory.c | 17 +++++++++++++++++
 lib/librte_eal/linux/eal_memalloc.c       |  3 +++
 2 files changed, 20 insertions(+)

diff --git a/lib/librte_eal/common/eal_common_memory.c 
b/lib/librte_eal/common/eal_common_memory.c
index cc7d54e0c..2fea1bdb2 100644
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -40,6 +40,14 @@
 static void *next_baseaddr;
 static uint64_t system_page_sz;
 
+#ifdef RTE_EXEC_ENV_LINUX
+#define RTE_DONTDUMP MADV_DONTDUMP
+#elif RTE_EXEC_ENV_FREEBSD
+#define RTE_DONTDUMP MADV_NOCORE
+#else
+#error "madvise doesn't support this OS"
+#endif
+
 #define MAX_MMAP_WITH_DEFINED_ADDR_TRIES 5
 void *
 eal_get_virtual_area(void *requested_addr, size_t *size,
@@ -179,6 +187,15 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
                        munmap(aligned_end, after_len);
        }
 
+    if (!unmap) {
+               /*
+                * Exclude this pages from a core dump.
+                */
+               if (madvise(aligned_addr, *size, MADV_DONTDUMP) != 0)
+                       RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
+                               strerror(errno));
+       }
+
        return aligned_addr;
 }
 
diff --git a/lib/librte_eal/linux/eal_memalloc.c 
b/lib/librte_eal/linux/eal_memalloc.c
index af6d0d023..f628e0991 100644
--- a/lib/librte_eal/linux/eal_memalloc.c
+++ b/lib/librte_eal/linux/eal_memalloc.c
@@ -687,6 +687,9 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
                return -1;
        }
 
+       if (madvise(ms->addr, ms->len, MADV_DONTDUMP) != 0)
+               RTE_LOG(DEBUG, EAL, "madvise failed: %s\n", strerror(errno));
+
        exit_early = false;
 
        /* if we're using anonymous hugepages, nothing to be done */
-- 
2.11.0


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