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[PATCH 4/5] elf2dmp: use Linux mmap with MAP_NORESERVE when possible
From: |
Viktor Prutyanov |
Subject: |
[PATCH 4/5] elf2dmp: use Linux mmap with MAP_NORESERVE when possible |
Date: |
Thu, 14 Sep 2023 01:46:56 +0300 |
Glib's g_mapped_file_new maps file with PROT_READ|PROT_WRITE and
MAP_PRIVATE. This leads to premature physical memory allocation of dump
file size on Linux hosts and may fail. On Linux, mapping the file with
MAP_NORESERVE limits the allocation by available memory.
Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
---
contrib/elf2dmp/qemu_elf.c | 66 +++++++++++++++++++++++++++++++-------
contrib/elf2dmp/qemu_elf.h | 4 +++
2 files changed, 58 insertions(+), 12 deletions(-)
diff --git a/contrib/elf2dmp/qemu_elf.c b/contrib/elf2dmp/qemu_elf.c
index ebda60dcb8..94a8c3ad15 100644
--- a/contrib/elf2dmp/qemu_elf.c
+++ b/contrib/elf2dmp/qemu_elf.c
@@ -165,10 +165,37 @@ static bool check_ehdr(QEMU_Elf *qe)
return true;
}
-int QEMU_Elf_init(QEMU_Elf *qe, const char *filename)
+static int QEMU_Elf_map(QEMU_Elf *qe, const char *filename)
{
+#ifdef CONFIG_LINUX
+ struct stat st;
+
+ printf("Using Linux's mmap\n");
+
+ qe->fd = open(filename, O_RDONLY, 0);
+ if (qe->fd == -1) {
+ eprintf("Failed to open ELF dump file \'%s\'\n", filename);
+ return 1;
+ }
+
+ if (fstat(qe->fd, &st)) {
+ eprintf("Failed to get size of ELF dump file\n");
+ close(qe->fd);
+ return 1;
+ }
+ qe->size = st.st_size;
+
+ qe->map = mmap(NULL, qe->size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_NORESERVE, qe->fd, 0);
+ if (qe->map == MAP_FAILED) {
+ eprintf("Failed to map ELF file\n");
+ close(qe->fd);
+ return 1;
+ }
+#else
GError *gerr = NULL;
- int err = 0;
+
+ printf("Using GLib's mmap\n");
qe->gmf = g_mapped_file_new(filename, TRUE, &gerr);
if (gerr) {
@@ -179,29 +206,44 @@ int QEMU_Elf_init(QEMU_Elf *qe, const char *filename)
qe->map = g_mapped_file_get_contents(qe->gmf);
qe->size = g_mapped_file_get_length(qe->gmf);
+#endif
+
+ return 0;
+}
+
+static void QEMU_Elf_unmap(QEMU_Elf *qe)
+{
+#ifdef CONFIG_LINUX
+ munmap(qe->map, qe->size);
+ close(qe->fd);
+#else
+ g_mapped_file_unref(qe->gmf);
+#endif
+}
+
+int QEMU_Elf_init(QEMU_Elf *qe, const char *filename)
+{
+ if (QEMU_Elf_map(qe, filename)) {
+ return 1;
+ }
if (!check_ehdr(qe)) {
eprintf("Input file has the wrong format\n");
- err = 1;
- goto out_unmap;
+ QEMU_Elf_unmap(qe);
+ return 1;
}
if (init_states(qe)) {
eprintf("Failed to extract QEMU CPU states\n");
- err = 1;
- goto out_unmap;
+ QEMU_Elf_unmap(qe);
+ return 1;
}
return 0;
-
-out_unmap:
- g_mapped_file_unref(qe->gmf);
-
- return err;
}
void QEMU_Elf_exit(QEMU_Elf *qe)
{
exit_states(qe);
- g_mapped_file_unref(qe->gmf);
+ QEMU_Elf_unmap(qe);
}
diff --git a/contrib/elf2dmp/qemu_elf.h b/contrib/elf2dmp/qemu_elf.h
index b2f0d9cbc9..2a71beca8e 100644
--- a/contrib/elf2dmp/qemu_elf.h
+++ b/contrib/elf2dmp/qemu_elf.h
@@ -32,7 +32,11 @@ typedef struct QEMUCPUState {
int is_system(QEMUCPUState *s);
typedef struct QEMU_Elf {
+#ifdef CONFIG_POSIX
+ int fd;
+#else
GMappedFile *gmf;
+#endif
size_t size;
void *map;
QEMUCPUState **state;
--
2.21.0