If the hostpage size is greater than the TARGET_PAGESIZE, the
target-pages of size TARGET_PAGESIZE are marked valid only till the
length requested during the elfload. The glibc attempts to consume unused
space in the last page of data segment(__libc_memalign() in
elf/dl-minimal.c). The GLRO(dl_pagesize) is actually the host pagesize as
set in the auxillary vectors. So, there is no explicit mmap request for
the remaining target-pages on the last hostpage. The glibc assumes that
particular space as available and subsequent attempts to use
those addresses lead to crash as the target_mmap has not marked them valid
for those target-pages.
The issue is seen when trying to chroot to 16.04-x86_64 ubuntu on a PPC64
host where the fork fails to access the thread_id as it is allocated on a
page not marked valid. The recent glibc doesnt have checks for thread-id in
fork, but the issue can manifest somewhere else, none the less.
The fix here is to map all the target-pages of the hostpage during the
ELF load for data segment to allow the glibc for proper consumption.
Signed-off-by: Shivaprasad G Bhat <sb...@linux.vnet.ibm.com>
---
linux-user/elfload.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 8638612aec..1d86034c8d 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1438,9 +1438,17 @@ struct exec
/* Necessary parameters */
#define TARGET_ELF_EXEC_PAGESIZE TARGET_PAGE_SIZE
-#define TARGET_ELF_PAGESTART(_v) ((_v) & \
- ~(abi_ulong)(TARGET_ELF_EXEC_PAGESIZE-1))
-#define TARGET_ELF_PAGEOFFSET(_v) ((_v) & (TARGET_ELF_EXEC_PAGESIZE-1))
+#define TARGET_ELF_PAGESTART(_v, _s) \
+ ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \
+ (_v) & ~(abi_ulong)(TARGET_ELF_EXEC_PAGESIZE - 1) : \
+ (_v) & ~(abi_ulong)(_s - 1));
+#define TARGET_ELF_PAGEOFFSET(_v, _s) \
+ ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \
+ (_v) & (TARGET_ELF_EXEC_PAGESIZE - 1) : \
+ (_v) & (_s - 1));
+#define TARGET_ELF_PAGELENGTH(_v, _s) \
+ ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \
+ TARGET_PAGE_ALIGN(_v) : HOST_PAGE_ALIGN(_v));
#define DLINFO_ITEMS 15
@@ -2279,7 +2287,7 @@ static void load_elf_image(const char *image_name, int
image_fd,
for (i = 0; i < ehdr->e_phnum; i++) {
struct elf_phdr *eppnt = phdr + i;
if (eppnt->p_type == PT_LOAD) {
- abi_ulong vaddr, vaddr_po, vaddr_ps, vaddr_ef, vaddr_em;
+ abi_ulong vaddr, vaddr_po, vaddr_ps, vaddr_ef, vaddr_em, vaddr_len;
int elf_prot = 0;
if (eppnt->p_flags & PF_R) elf_prot = PROT_READ;
@@ -2287,10 +2295,12 @@ static void load_elf_image(const char *image_name, int
image_fd,
if (eppnt->p_flags & PF_X) elf_prot |= PROT_EXEC;
vaddr = load_bias + eppnt->p_vaddr;
- vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr);
- vaddr_ps = TARGET_ELF_PAGESTART(vaddr);
+ vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr, qemu_host_page_size);
+ vaddr_ps = TARGET_ELF_PAGESTART(vaddr, qemu_host_page_size);
+ vaddr_len = TARGET_ELF_PAGELENGTH(eppnt->p_filesz + vaddr_po,
+ qemu_host_page_size);
- error = target_mmap(vaddr_ps, eppnt->p_filesz + vaddr_po,
+ error = target_mmap(vaddr_ps, vaddr_len,
elf_prot, MAP_PRIVATE | MAP_FIXED,
image_fd, eppnt->p_offset - vaddr_po);
if (error == -1) {
