| Message ID | 153546966871.75539.10980006517656536139.stgit@lep8c.aus.stglabs.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] linux-user: elf: mmap all the target-pages of hostpage for data segment | expand |
Le 28/08/2018 à 17:22, Shivaprasad G Bhat a écrit : > 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). If PT_LOAD p_align is greater than or > equal to hostpage size, 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 target-pages as valid. > > 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 > elfload if the p_align is greater than or equal to hostpage size, for > data segment to allow the glibc for proper consumption. > > Signed-off-by: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com> > --- > v1: https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg05730.html > Changes from v1: > - Made the conditionals consistent with the commit "33143c446e" and > changed the commit message accordingly. > > linux-user/elfload.c | 37 +++++++++++++++++++++++++++++-------- > 1 file changed, 29 insertions(+), 8 deletions(-) > > diff --git a/linux-user/elfload.c b/linux-user/elfload.c > index 8638612aec..cced43f45c 100644 > --- a/linux-user/elfload.c > +++ b/linux-user/elfload.c > @@ -1438,9 +1438,23 @@ 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, _a, _s, _m) \ > + (((_a & ~_m) != 0) ? \ > + (_v) & ~(abi_ulong)(TARGET_ELF_EXEC_PAGESIZE - 1) : \ > + ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \ > + (_v) & ~(abi_ulong)(TARGET_ELF_EXEC_PAGESIZE - 1) : \ > + (_v) & ~(abi_ulong)(_s - 1))); > +#define TARGET_ELF_PAGEOFFSET(_v, _a, _s, _m) \ > + (((_a & ~_m) != 0) ? \ > + (_v) & (TARGET_ELF_EXEC_PAGESIZE - 1) : \ > + ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \ > + (_v) & (TARGET_ELF_EXEC_PAGESIZE - 1) : \ > + (_v) & (_s - 1))); > +#define TARGET_ELF_PAGELENGTH(_v, _a, _s, _m) \ > + (((_a & ~_m) != 0) ? \ > + TARGET_PAGE_ALIGN(_v) : \ > + ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \ > + TARGET_PAGE_ALIGN(_v) : HOST_PAGE_ALIGN(_v))); I think you should use eppnt->p_align instead of info->alignment and simplify this to: #define TARGET_ELF_EXEC_PAGESIZE \ (((eppnt->p_align & ~qemu_host_page_mask) != 0) ? \ TARGET_PAGE_SIZE : MAX(qemu_host_page_size, TARGET_PAGE_SIZE)) #define TARGET_ELF_PAGELENGTH(_v) ROUND_UP((_v), TARGET_ELF_EXEC_PAGESIZE) Thanks, Laurent
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 8638612aec..cced43f45c 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -1438,9 +1438,23 @@ 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, _a, _s, _m) \ + (((_a & ~_m) != 0) ? \ + (_v) & ~(abi_ulong)(TARGET_ELF_EXEC_PAGESIZE - 1) : \ + ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \ + (_v) & ~(abi_ulong)(TARGET_ELF_EXEC_PAGESIZE - 1) : \ + (_v) & ~(abi_ulong)(_s - 1))); +#define TARGET_ELF_PAGEOFFSET(_v, _a, _s, _m) \ + (((_a & ~_m) != 0) ? \ + (_v) & (TARGET_ELF_EXEC_PAGESIZE - 1) : \ + ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \ + (_v) & (TARGET_ELF_EXEC_PAGESIZE - 1) : \ + (_v) & (_s - 1))); +#define TARGET_ELF_PAGELENGTH(_v, _a, _s, _m) \ + (((_a & ~_m) != 0) ? \ + TARGET_PAGE_ALIGN(_v) : \ + ((TARGET_ELF_EXEC_PAGESIZE > _s) ? \ + TARGET_PAGE_ALIGN(_v) : HOST_PAGE_ALIGN(_v))); #define DLINFO_ITEMS 15 @@ -2279,7 +2293,7 @@ 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 +2301,17 @@ 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); - - error = target_mmap(vaddr_ps, eppnt->p_filesz + vaddr_po, + vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr, info->alignment, + qemu_host_page_size, + qemu_host_page_mask); + vaddr_ps = TARGET_ELF_PAGESTART(vaddr, info->alignment, + qemu_host_page_size, + qemu_host_page_mask); + vaddr_len = TARGET_ELF_PAGELENGTH(eppnt->p_filesz + vaddr_po, + info->alignment, + qemu_host_page_size, + qemu_host_page_mask); + error = target_mmap(vaddr_ps, vaddr_len, elf_prot, MAP_PRIVATE | MAP_FIXED, image_fd, eppnt->p_offset - vaddr_po); if (error == -1) {
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). If PT_LOAD p_align is greater than or equal to hostpage size, 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 target-pages as valid. 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 elfload if the p_align is greater than or equal to hostpage size, for data segment to allow the glibc for proper consumption. Signed-off-by: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com> --- v1: https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg05730.html Changes from v1: - Made the conditionals consistent with the commit "33143c446e" and changed the commit message accordingly. linux-user/elfload.c | 37 +++++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-)