| Message ID | 20230801232745.4125-9-deller@gmx.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | linux-user: brk fixes | expand |
On 2023/08/02 8:27, Helge Deller wrote: > Fix the elf loader to calculate a valid TASK_UNMAPPED_BASE address for all > 32-bit architectures, based on the GUEST_ADDR_MAX constant. > > Additionally modify the elf loader to load dynamic pie executables at > around: > ~ 0x5500000000 for 64-bit guest binaries on 64-bit host, > - 0x00300000 for 32-bit guest binaries on 64-bit host, and > - 0x00000000 for 32-bit guest binaries on 32-bit host. Why do you change guest addresses depending on the host? > > With this patch the Thread Sanitizer (TSan) application will work again, > as in commit aab613fb9597 ("linux-user: Update TASK_UNMAPPED_BASE for > aarch64"). > > Signed-off-by: Helge Deller <deller@gmx.de> > --- > linux-user/elfload.c | 6 ++++-- > linux-user/loader.h | 12 ++++++++++++ > linux-user/mmap.c | 35 ++++++++++++++++++----------------- > 3 files changed, 34 insertions(+), 19 deletions(-) > > diff --git a/linux-user/elfload.c b/linux-user/elfload.c > index 47a118e430..8f5a79b537 100644 > --- a/linux-user/elfload.c > +++ b/linux-user/elfload.c > @@ -3021,6 +3021,7 @@ static void load_elf_image(const char *image_name, int image_fd, > struct elfhdr *ehdr = (struct elfhdr *)bprm_buf; > struct elf_phdr *phdr; > abi_ulong load_addr, load_bias, loaddr, hiaddr, error; > + unsigned long load_offset = 0; > int i, retval, prot_exec; > Error *err = NULL; > bool is_main_executable; > @@ -3121,6 +3122,7 @@ static void load_elf_image(const char *image_name, int image_fd, > * select guest_base. In this case we pass a size. > */ > probe_guest_base(image_name, 0, hiaddr - loaddr); > + load_offset = TASK_UNMAPPED_BASE_PIE; > } > } > > @@ -3138,7 +3140,7 @@ static void load_elf_image(const char *image_name, int image_fd, > * In both cases, we will overwrite pages in this range with mappings > * from the executable. > */ > - load_addr = target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, PROT_NONE, > + load_addr = target_mmap(loaddr + load_offset, (size_t)hiaddr - loaddr + 1, PROT_NONE, > MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | > (is_main_executable ? MAP_FIXED : 0), > -1, 0); > @@ -3176,7 +3178,7 @@ static void load_elf_image(const char *image_name, int image_fd, > info->start_data = -1; > info->end_data = 0; > /* possible start for brk is behind all sections of this ELF file. */ > - info->brk = TARGET_PAGE_ALIGN(hiaddr); > + info->brk = TARGET_PAGE_ALIGN(load_offset + hiaddr); > info->elf_flags = ehdr->e_flags; > > prot_exec = PROT_EXEC; > diff --git a/linux-user/loader.h b/linux-user/loader.h > index 59cbeacf24..3bbfc108eb 100644 > --- a/linux-user/loader.h > +++ b/linux-user/loader.h > @@ -18,6 +18,18 @@ > #ifndef LINUX_USER_LOADER_H > #define LINUX_USER_LOADER_H > > +/* where to map binaries? */ > +#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 > +# define TASK_UNMAPPED_BASE_PIE 0x5500000000 > +# define TASK_UNMAPPED_BASE 0x7000000000 > +#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 > +# define TASK_UNMAPPED_BASE_PIE 0x00300000 > +# define TASK_UNMAPPED_BASE (GUEST_ADDR_MAX - 0x20000000 + 1) > +#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ > +# define TASK_UNMAPPED_BASE_PIE 0x00000000 > +# define TASK_UNMAPPED_BASE 0x40000000 > +#endif > + > /* > * Read a good amount of data initially, to hopefully get all the > * program headers loaded. > diff --git a/linux-user/mmap.c b/linux-user/mmap.c > index c624feead0..3441198e21 100644 > --- a/linux-user/mmap.c > +++ b/linux-user/mmap.c > @@ -23,6 +23,7 @@ > #include "user-internals.h" > #include "user-mmap.h" > #include "target_mman.h" > +#include "loader.h" > > static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER; > static __thread int mmap_lock_count; > @@ -295,23 +296,6 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, > return true; > } > > -#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 > -#ifdef TARGET_AARCH64 > -# define TASK_UNMAPPED_BASE 0x5500000000 > -#else > -# define TASK_UNMAPPED_BASE 0x4000000000 > -#endif > -#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 > -#ifdef TARGET_HPPA > -# define TASK_UNMAPPED_BASE 0xfa000000 > -#else > -# define TASK_UNMAPPED_BASE 0xe0000000 > -#endif > -#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ > -# define TASK_UNMAPPED_BASE 0x40000000 > -#endif > -abi_ulong mmap_next_start = TASK_UNMAPPED_BASE; > - > unsigned long last_brk; > > /* > @@ -344,6 +328,23 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align) > abi_ulong addr; > int wrapped, repeat; > > + static abi_ulong mmap_next_start; > + > + /* initialize mmap_next_start if necessary */ > + if (!mmap_next_start) { > + mmap_next_start = TASK_UNMAPPED_BASE; > + > + /* do sanity checks on guest memory layout */ > + if (mmap_next_start >= GUEST_ADDR_MAX) { > + mmap_next_start = GUEST_ADDR_MAX - 0x1000000000 + 1; What if GUEST_ADDR_MAX < 0x1000000000? I think you can just return a hard error when mmap_next_start >= GUEST_ADDR_MAX. > + } > + > + if (TASK_UNMAPPED_BASE_PIE >= mmap_next_start) { > + fprintf(stderr, "Memory too small for PIE executables.\n"); Perhaps it's better to use error_report() for new code. > + exit(EXIT_FAILURE); > + } > + } > + > align = MAX(align, qemu_host_page_size); > > /* If 'start' == 0, then a default start address is used. */ > -- > 2.41.0 >
On 8/2/23 09:49, Akihiko Odaki wrote: > On 2023/08/02 8:27, Helge Deller wrote: >> Fix the elf loader to calculate a valid TASK_UNMAPPED_BASE address for all >> 32-bit architectures, based on the GUEST_ADDR_MAX constant. >> >> Additionally modify the elf loader to load dynamic pie executables at >> around: >> ~ 0x5500000000 for 64-bit guest binaries on 64-bit host, >> - 0x00300000 for 32-bit guest binaries on 64-bit host, and >> - 0x00000000 for 32-bit guest binaries on 32-bit host. > > Why do you change guest addresses depending on the host? The addresses are guest-addresses. A 32-bit guest PIE can't be loaded at e.g. 0x5500000000, while a 64-bit guest PIE needs to be loaded at 0x5500000000. >> With this patch the Thread Sanitizer (TSan) application will work again, >> as in commit aab613fb9597 ("linux-user: Update TASK_UNMAPPED_BASE for >> aarch64"). >> >> Signed-off-by: Helge Deller <deller@gmx.de> >> --- >> linux-user/elfload.c | 6 ++++-- >> linux-user/loader.h | 12 ++++++++++++ >> linux-user/mmap.c | 35 ++++++++++++++++++----------------- >> 3 files changed, 34 insertions(+), 19 deletions(-) >> >> diff --git a/linux-user/elfload.c b/linux-user/elfload.c >> index 47a118e430..8f5a79b537 100644 >> --- a/linux-user/elfload.c >> +++ b/linux-user/elfload.c >> @@ -3021,6 +3021,7 @@ static void load_elf_image(const char *image_name, int image_fd, >> struct elfhdr *ehdr = (struct elfhdr *)bprm_buf; >> struct elf_phdr *phdr; >> abi_ulong load_addr, load_bias, loaddr, hiaddr, error; >> + unsigned long load_offset = 0; >> int i, retval, prot_exec; >> Error *err = NULL; >> bool is_main_executable; >> @@ -3121,6 +3122,7 @@ static void load_elf_image(const char *image_name, int image_fd, >> * select guest_base. In this case we pass a size. >> */ >> probe_guest_base(image_name, 0, hiaddr - loaddr); >> + load_offset = TASK_UNMAPPED_BASE_PIE; >> } >> } >> >> @@ -3138,7 +3140,7 @@ static void load_elf_image(const char *image_name, int image_fd, >> * In both cases, we will overwrite pages in this range with mappings >> * from the executable. >> */ >> - load_addr = target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, PROT_NONE, >> + load_addr = target_mmap(loaddr + load_offset, (size_t)hiaddr - loaddr + 1, PROT_NONE, >> MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | >> (is_main_executable ? MAP_FIXED : 0), >> -1, 0); >> @@ -3176,7 +3178,7 @@ static void load_elf_image(const char *image_name, int image_fd, >> info->start_data = -1; >> info->end_data = 0; >> /* possible start for brk is behind all sections of this ELF file. */ >> - info->brk = TARGET_PAGE_ALIGN(hiaddr); >> + info->brk = TARGET_PAGE_ALIGN(load_offset + hiaddr); >> info->elf_flags = ehdr->e_flags; >> >> prot_exec = PROT_EXEC; >> diff --git a/linux-user/loader.h b/linux-user/loader.h >> index 59cbeacf24..3bbfc108eb 100644 >> --- a/linux-user/loader.h >> +++ b/linux-user/loader.h >> @@ -18,6 +18,18 @@ >> #ifndef LINUX_USER_LOADER_H >> #define LINUX_USER_LOADER_H >> >> +/* where to map binaries? */ >> +#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 >> +# define TASK_UNMAPPED_BASE_PIE 0x5500000000 >> +# define TASK_UNMAPPED_BASE 0x7000000000 >> +#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 >> +# define TASK_UNMAPPED_BASE_PIE 0x00300000 >> +# define TASK_UNMAPPED_BASE (GUEST_ADDR_MAX - 0x20000000 + 1) >> +#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ >> +# define TASK_UNMAPPED_BASE_PIE 0x00000000 >> +# define TASK_UNMAPPED_BASE 0x40000000 >> +#endif >> + >> /* >> * Read a good amount of data initially, to hopefully get all the >> * program headers loaded. >> diff --git a/linux-user/mmap.c b/linux-user/mmap.c >> index c624feead0..3441198e21 100644 >> --- a/linux-user/mmap.c >> +++ b/linux-user/mmap.c >> @@ -23,6 +23,7 @@ >> #include "user-internals.h" >> #include "user-mmap.h" >> #include "target_mman.h" >> +#include "loader.h" >> >> static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER; >> static __thread int mmap_lock_count; >> @@ -295,23 +296,6 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, >> return true; >> } >> >> -#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 >> -#ifdef TARGET_AARCH64 >> -# define TASK_UNMAPPED_BASE 0x5500000000 >> -#else >> -# define TASK_UNMAPPED_BASE 0x4000000000 >> -#endif >> -#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 >> -#ifdef TARGET_HPPA >> -# define TASK_UNMAPPED_BASE 0xfa000000 >> -#else >> -# define TASK_UNMAPPED_BASE 0xe0000000 >> -#endif >> -#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ >> -# define TASK_UNMAPPED_BASE 0x40000000 >> -#endif >> -abi_ulong mmap_next_start = TASK_UNMAPPED_BASE; >> - >> unsigned long last_brk; >> >> /* >> @@ -344,6 +328,23 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align) >> abi_ulong addr; >> int wrapped, repeat; >> >> + static abi_ulong mmap_next_start; >> + >> + /* initialize mmap_next_start if necessary */ >> + if (!mmap_next_start) { >> + mmap_next_start = TASK_UNMAPPED_BASE; >> + >> + /* do sanity checks on guest memory layout */ >> + if (mmap_next_start >= GUEST_ADDR_MAX) { >> + mmap_next_start = GUEST_ADDR_MAX - 0x1000000000 + 1; > > What if GUEST_ADDR_MAX < 0x1000000000? this check affects 64-bit executables only where GUEST_ADDR_MAX is bigger than that number. But I agree it's not directly visible from the code. 32-bit ones are taken care of where TASK_UNMAPPED_BASE is defined. > I think you can just return a hard error when mmap_next_start >= GUEST_ADDR_MAX. Can't happen, but I will rewrite it. >> + } >> + >> + if (TASK_UNMAPPED_BASE_PIE >= mmap_next_start) { >> + fprintf(stderr, "Memory too small for PIE executables.\n"); > > Perhaps it's better to use error_report() for new code. Ok. Helge
On 2023/08/02 17:42, Helge Deller wrote: > On 8/2/23 09:49, Akihiko Odaki wrote: >> On 2023/08/02 8:27, Helge Deller wrote: >>> Fix the elf loader to calculate a valid TASK_UNMAPPED_BASE address >>> for all >>> 32-bit architectures, based on the GUEST_ADDR_MAX constant. >>> >>> Additionally modify the elf loader to load dynamic pie executables at >>> around: >>> ~ 0x5500000000 for 64-bit guest binaries on 64-bit host, >>> - 0x00300000 for 32-bit guest binaries on 64-bit host, and >>> - 0x00000000 for 32-bit guest binaries on 32-bit host. >> >> Why do you change guest addresses depending on the host? > > The addresses are guest-addresses. > A 32-bit guest PIE can't be loaded at e.g. 0x5500000000, > while a 64-bit guest PIE needs to be loaded at 0x5500000000. I mean, why do you use address 0x00000000 for 32-bit guest binaries on 32-bit host while you use address 0x00300000 on 64-bit host? > >>> With this patch the Thread Sanitizer (TSan) application will work again, >>> as in commit aab613fb9597 ("linux-user: Update TASK_UNMAPPED_BASE for >>> aarch64"). >>> >>> Signed-off-by: Helge Deller <deller@gmx.de> >>> --- >>> linux-user/elfload.c | 6 ++++-- >>> linux-user/loader.h | 12 ++++++++++++ >>> linux-user/mmap.c | 35 ++++++++++++++++++----------------- >>> 3 files changed, 34 insertions(+), 19 deletions(-) >>> >>> diff --git a/linux-user/elfload.c b/linux-user/elfload.c >>> index 47a118e430..8f5a79b537 100644 >>> --- a/linux-user/elfload.c >>> +++ b/linux-user/elfload.c >>> @@ -3021,6 +3021,7 @@ static void load_elf_image(const char >>> *image_name, int image_fd, >>> struct elfhdr *ehdr = (struct elfhdr *)bprm_buf; >>> struct elf_phdr *phdr; >>> abi_ulong load_addr, load_bias, loaddr, hiaddr, error; >>> + unsigned long load_offset = 0; >>> int i, retval, prot_exec; >>> Error *err = NULL; >>> bool is_main_executable; >>> @@ -3121,6 +3122,7 @@ static void load_elf_image(const char >>> *image_name, int image_fd, >>> * select guest_base. In this case we pass a size. >>> */ >>> probe_guest_base(image_name, 0, hiaddr - loaddr); >>> + load_offset = TASK_UNMAPPED_BASE_PIE; >>> } >>> } >>> >>> @@ -3138,7 +3140,7 @@ static void load_elf_image(const char >>> *image_name, int image_fd, >>> * In both cases, we will overwrite pages in this range with >>> mappings >>> * from the executable. >>> */ >>> - load_addr = target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, >>> PROT_NONE, >>> + load_addr = target_mmap(loaddr + load_offset, (size_t)hiaddr - >>> loaddr + 1, PROT_NONE, >>> MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | >>> (is_main_executable ? MAP_FIXED : 0), >>> -1, 0); >>> @@ -3176,7 +3178,7 @@ static void load_elf_image(const char >>> *image_name, int image_fd, >>> info->start_data = -1; >>> info->end_data = 0; >>> /* possible start for brk is behind all sections of this ELF >>> file. */ >>> - info->brk = TARGET_PAGE_ALIGN(hiaddr); >>> + info->brk = TARGET_PAGE_ALIGN(load_offset + hiaddr); >>> info->elf_flags = ehdr->e_flags; >>> >>> prot_exec = PROT_EXEC; >>> diff --git a/linux-user/loader.h b/linux-user/loader.h >>> index 59cbeacf24..3bbfc108eb 100644 >>> --- a/linux-user/loader.h >>> +++ b/linux-user/loader.h >>> @@ -18,6 +18,18 @@ >>> #ifndef LINUX_USER_LOADER_H >>> #define LINUX_USER_LOADER_H >>> >>> +/* where to map binaries? */ >>> +#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 >>> +# define TASK_UNMAPPED_BASE_PIE 0x5500000000 >>> +# define TASK_UNMAPPED_BASE 0x7000000000 >>> +#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 >>> +# define TASK_UNMAPPED_BASE_PIE 0x00300000 >>> +# define TASK_UNMAPPED_BASE (GUEST_ADDR_MAX - 0x20000000 + 1) >>> +#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ >>> +# define TASK_UNMAPPED_BASE_PIE 0x00000000 >>> +# define TASK_UNMAPPED_BASE 0x40000000 >>> +#endif >>> + >>> /* >>> * Read a good amount of data initially, to hopefully get all the >>> * program headers loaded. >>> diff --git a/linux-user/mmap.c b/linux-user/mmap.c >>> index c624feead0..3441198e21 100644 >>> --- a/linux-user/mmap.c >>> +++ b/linux-user/mmap.c >>> @@ -23,6 +23,7 @@ >>> #include "user-internals.h" >>> #include "user-mmap.h" >>> #include "target_mman.h" >>> +#include "loader.h" >>> >>> static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER; >>> static __thread int mmap_lock_count; >>> @@ -295,23 +296,6 @@ static bool mmap_frag(abi_ulong real_start, >>> abi_ulong start, abi_ulong last, >>> return true; >>> } >>> >>> -#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 >>> -#ifdef TARGET_AARCH64 >>> -# define TASK_UNMAPPED_BASE 0x5500000000 >>> -#else >>> -# define TASK_UNMAPPED_BASE 0x4000000000 >>> -#endif >>> -#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 >>> -#ifdef TARGET_HPPA >>> -# define TASK_UNMAPPED_BASE 0xfa000000 >>> -#else >>> -# define TASK_UNMAPPED_BASE 0xe0000000 >>> -#endif >>> -#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ >>> -# define TASK_UNMAPPED_BASE 0x40000000 >>> -#endif >>> -abi_ulong mmap_next_start = TASK_UNMAPPED_BASE; >>> - >>> unsigned long last_brk; >>> >>> /* >>> @@ -344,6 +328,23 @@ abi_ulong mmap_find_vma(abi_ulong start, >>> abi_ulong size, abi_ulong align) >>> abi_ulong addr; >>> int wrapped, repeat; >>> >>> + static abi_ulong mmap_next_start; >>> + >>> + /* initialize mmap_next_start if necessary */ >>> + if (!mmap_next_start) { >>> + mmap_next_start = TASK_UNMAPPED_BASE; >>> + >>> + /* do sanity checks on guest memory layout */ >>> + if (mmap_next_start >= GUEST_ADDR_MAX) { >>> + mmap_next_start = GUEST_ADDR_MAX - 0x1000000000 + 1; >> >> What if GUEST_ADDR_MAX < 0x1000000000? > > this check affects 64-bit executables only where GUEST_ADDR_MAX is bigger > than that number. But I agree it's not directly visible from the code. > 32-bit ones are taken care of where TASK_UNMAPPED_BASE is defined. > >> I think you can just return a hard error when mmap_next_start >= >> GUEST_ADDR_MAX. > > Can't happen, but I will rewrite it. > >>> + } >>> + >>> + if (TASK_UNMAPPED_BASE_PIE >= mmap_next_start) { >>> + fprintf(stderr, "Memory too small for PIE executables.\n"); >> >> Perhaps it's better to use error_report() for new code. > > Ok. > > Helge
On 8/2/23 10:44, Akihiko Odaki wrote: > On 2023/08/02 17:42, Helge Deller wrote: >> On 8/2/23 09:49, Akihiko Odaki wrote: >>> On 2023/08/02 8:27, Helge Deller wrote: >>>> Fix the elf loader to calculate a valid TASK_UNMAPPED_BASE address for all >>>> 32-bit architectures, based on the GUEST_ADDR_MAX constant. >>>> >>>> Additionally modify the elf loader to load dynamic pie executables at >>>> around: >>>> ~ 0x5500000000 for 64-bit guest binaries on 64-bit host, >>>> - 0x00300000 for 32-bit guest binaries on 64-bit host, and >>>> - 0x00000000 for 32-bit guest binaries on 32-bit host. >>> >>> Why do you change guest addresses depending on the host? >> >> The addresses are guest-addresses. >> A 32-bit guest PIE can't be loaded at e.g. 0x5500000000, >> while a 64-bit guest PIE needs to be loaded at 0x5500000000. > > I mean, why do you use address 0x00000000 for 32-bit guest binaries on 32-bit host while you use address 0x00300000 on 64-bit host? To keep the memory pressure for the 32-bit qemu binary minimal. On 64-bit host we have the full 32-bit address space for the guest. Helge
On 2023/08/02 18:34, Helge Deller wrote: > On 8/2/23 10:44, Akihiko Odaki wrote: >> On 2023/08/02 17:42, Helge Deller wrote: >>> On 8/2/23 09:49, Akihiko Odaki wrote: >>>> On 2023/08/02 8:27, Helge Deller wrote: >>>>> Fix the elf loader to calculate a valid TASK_UNMAPPED_BASE address >>>>> for all >>>>> 32-bit architectures, based on the GUEST_ADDR_MAX constant. >>>>> >>>>> Additionally modify the elf loader to load dynamic pie executables at >>>>> around: >>>>> ~ 0x5500000000 for 64-bit guest binaries on 64-bit host, >>>>> - 0x00300000 for 32-bit guest binaries on 64-bit host, and >>>>> - 0x00000000 for 32-bit guest binaries on 32-bit host. >>>> >>>> Why do you change guest addresses depending on the host? >>> >>> The addresses are guest-addresses. >>> A 32-bit guest PIE can't be loaded at e.g. 0x5500000000, >>> while a 64-bit guest PIE needs to be loaded at 0x5500000000. >> >> I mean, why do you use address 0x00000000 for 32-bit guest binaries on >> 32-bit host while you use address 0x00300000 on 64-bit host? > > To keep the memory pressure for the 32-bit qemu binary minimal. > On 64-bit host we have the full 32-bit address space for the guest. > > Helge > That makes sense. I'm worried that using 0x00000000 may break NULL checks on the guest though. Regards, Akihiko Odaki
On 8/2/23 11:58, Akihiko Odaki wrote: > On 2023/08/02 18:34, Helge Deller wrote: >> On 8/2/23 10:44, Akihiko Odaki wrote: >>> On 2023/08/02 17:42, Helge Deller wrote: >>>> On 8/2/23 09:49, Akihiko Odaki wrote: >>>>> On 2023/08/02 8:27, Helge Deller wrote: >>>>>> Fix the elf loader to calculate a valid TASK_UNMAPPED_BASE address for all >>>>>> 32-bit architectures, based on the GUEST_ADDR_MAX constant. >>>>>> >>>>>> Additionally modify the elf loader to load dynamic pie executables at >>>>>> around: >>>>>> ~ 0x5500000000 for 64-bit guest binaries on 64-bit host, >>>>>> - 0x00300000 for 32-bit guest binaries on 64-bit host, and >>>>>> - 0x00000000 for 32-bit guest binaries on 32-bit host. >>>>> >>>>> Why do you change guest addresses depending on the host? >>>> >>>> The addresses are guest-addresses. >>>> A 32-bit guest PIE can't be loaded at e.g. 0x5500000000, >>>> while a 64-bit guest PIE needs to be loaded at 0x5500000000. >>> >>> I mean, why do you use address 0x00000000 for 32-bit guest binaries on 32-bit host while you use address 0x00300000 on 64-bit host? >> >> To keep the memory pressure for the 32-bit qemu binary minimal. >> On 64-bit host we have the full 32-bit address space for the guest. >> >> Helge >> > > That makes sense. I'm worried that using 0x00000000 may break NULL checks on the guest though. probably not, because 0 means to search any free space. It's not fixed, it will be searched from there. Helge
On 8/1/23 16:27, Helge Deller wrote: > +/* where to map binaries? */ > +#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 > +# define TASK_UNMAPPED_BASE_PIE 0x5500000000 > +# define TASK_UNMAPPED_BASE 0x7000000000 > +#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 > +# define TASK_UNMAPPED_BASE_PIE 0x00300000 > +# define TASK_UNMAPPED_BASE (GUEST_ADDR_MAX - 0x20000000 + 1) > +#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ > +# define TASK_UNMAPPED_BASE_PIE 0x00000000 > +# define TASK_UNMAPPED_BASE 0x40000000 > +#endif It would probably be easier to follow if you use the kernel's name: ELF_ET_DYN_BASE. Should be in linux-user/$GUEST/target_mmap.h with TASK_UNMAPPED_BASE, per my comment vs patch 7. > + /* do sanity checks on guest memory layout */ > + if (mmap_next_start >= GUEST_ADDR_MAX) { > + mmap_next_start = GUEST_ADDR_MAX - 0x1000000000 + 1; > + } What in the world is that random number? It certainly won't compile on 32-bit host, and certainly isn't relevant to a 32-bit guest. > + if (TASK_UNMAPPED_BASE_PIE >= mmap_next_start) { > + fprintf(stderr, "Memory too small for PIE executables.\n"); > + exit(EXIT_FAILURE); > + } Really bad timing for this diagnostic. What if a PIE executable isn't even being used? Both TASK_UNMAPPED_BASE and ELF_ET_DYN_BASE could be computed in main (or a subroutine), when reserved_va is assigned. r~
On 8/2/23 20:36, Richard Henderson wrote: > On 8/1/23 16:27, Helge Deller wrote: >> +/* where to map binaries? */ >> +#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 >> +# define TASK_UNMAPPED_BASE_PIE 0x5500000000 >> +# define TASK_UNMAPPED_BASE 0x7000000000 >> +#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 >> +# define TASK_UNMAPPED_BASE_PIE 0x00300000 >> +# define TASK_UNMAPPED_BASE (GUEST_ADDR_MAX - 0x20000000 + 1) >> +#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ >> +# define TASK_UNMAPPED_BASE_PIE 0x00000000 >> +# define TASK_UNMAPPED_BASE 0x40000000 >> +#endif > > It would probably be easier to follow if you use the kernel's name: > ELF_ET_DYN_BASE. Agreed. > Should be in linux-user/$GUEST/target_mmap.h with > TASK_UNMAPPED_BASE, per my comment vs patch 7. Maybe, but see my comments/answers there... >> + /* do sanity checks on guest memory layout */ >> + if (mmap_next_start >= GUEST_ADDR_MAX) { >> + mmap_next_start = GUEST_ADDR_MAX - 0x1000000000 + 1; >> + } > > What in the world is that random number? It's random. Idea is to keep enough space for shared libs below GUEST_ADDR_MAX. > It certainly won't compile > on 32-bit host, and certainly isn't relevant to a 32-bit guest. That code will never be compiled/executed on 32-bit guests & hosts. The defines for TASK_UNMAPPED_BASE take already care of that. But I agree it's not directly visible (and probably not nice that way). >> + if (TASK_UNMAPPED_BASE_PIE >= mmap_next_start) { >> + fprintf(stderr, "Memory too small for PIE executables.\n"); >> + exit(EXIT_FAILURE); >> + } > > Really bad timing for this diagnostic. What if a PIE executable isn't even being used? > > Both TASK_UNMAPPED_BASE and ELF_ET_DYN_BASE could be computed in main (or a subroutine), when reserved_va is assigned. Helge
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 47a118e430..8f5a79b537 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -3021,6 +3021,7 @@ static void load_elf_image(const char *image_name, int image_fd, struct elfhdr *ehdr = (struct elfhdr *)bprm_buf; struct elf_phdr *phdr; abi_ulong load_addr, load_bias, loaddr, hiaddr, error; + unsigned long load_offset = 0; int i, retval, prot_exec; Error *err = NULL; bool is_main_executable; @@ -3121,6 +3122,7 @@ static void load_elf_image(const char *image_name, int image_fd, * select guest_base. In this case we pass a size. */ probe_guest_base(image_name, 0, hiaddr - loaddr); + load_offset = TASK_UNMAPPED_BASE_PIE; } } @@ -3138,7 +3140,7 @@ static void load_elf_image(const char *image_name, int image_fd, * In both cases, we will overwrite pages in this range with mappings * from the executable. */ - load_addr = target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, PROT_NONE, + load_addr = target_mmap(loaddr + load_offset, (size_t)hiaddr - loaddr + 1, PROT_NONE, MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | (is_main_executable ? MAP_FIXED : 0), -1, 0); @@ -3176,7 +3178,7 @@ static void load_elf_image(const char *image_name, int image_fd, info->start_data = -1; info->end_data = 0; /* possible start for brk is behind all sections of this ELF file. */ - info->brk = TARGET_PAGE_ALIGN(hiaddr); + info->brk = TARGET_PAGE_ALIGN(load_offset + hiaddr); info->elf_flags = ehdr->e_flags; prot_exec = PROT_EXEC; diff --git a/linux-user/loader.h b/linux-user/loader.h index 59cbeacf24..3bbfc108eb 100644 --- a/linux-user/loader.h +++ b/linux-user/loader.h @@ -18,6 +18,18 @@ #ifndef LINUX_USER_LOADER_H #define LINUX_USER_LOADER_H +/* where to map binaries? */ +#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 +# define TASK_UNMAPPED_BASE_PIE 0x5500000000 +# define TASK_UNMAPPED_BASE 0x7000000000 +#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 +# define TASK_UNMAPPED_BASE_PIE 0x00300000 +# define TASK_UNMAPPED_BASE (GUEST_ADDR_MAX - 0x20000000 + 1) +#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ +# define TASK_UNMAPPED_BASE_PIE 0x00000000 +# define TASK_UNMAPPED_BASE 0x40000000 +#endif + /* * Read a good amount of data initially, to hopefully get all the * program headers loaded. diff --git a/linux-user/mmap.c b/linux-user/mmap.c index c624feead0..3441198e21 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -23,6 +23,7 @@ #include "user-internals.h" #include "user-mmap.h" #include "target_mman.h" +#include "loader.h" static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER; static __thread int mmap_lock_count; @@ -295,23 +296,6 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, return true; } -#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64 -#ifdef TARGET_AARCH64 -# define TASK_UNMAPPED_BASE 0x5500000000 -#else -# define TASK_UNMAPPED_BASE 0x4000000000 -#endif -#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 -#ifdef TARGET_HPPA -# define TASK_UNMAPPED_BASE 0xfa000000 -#else -# define TASK_UNMAPPED_BASE 0xe0000000 -#endif -#else /* HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32 */ -# define TASK_UNMAPPED_BASE 0x40000000 -#endif -abi_ulong mmap_next_start = TASK_UNMAPPED_BASE; - unsigned long last_brk; /* @@ -344,6 +328,23 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align) abi_ulong addr; int wrapped, repeat; + static abi_ulong mmap_next_start; + + /* initialize mmap_next_start if necessary */ + if (!mmap_next_start) { + mmap_next_start = TASK_UNMAPPED_BASE; + + /* do sanity checks on guest memory layout */ + if (mmap_next_start >= GUEST_ADDR_MAX) { + mmap_next_start = GUEST_ADDR_MAX - 0x1000000000 + 1; + } + + if (TASK_UNMAPPED_BASE_PIE >= mmap_next_start) { + fprintf(stderr, "Memory too small for PIE executables.\n"); + exit(EXIT_FAILURE); + } + } + align = MAX(align, qemu_host_page_size); /* If 'start' == 0, then a default start address is used. */
Fix the elf loader to calculate a valid TASK_UNMAPPED_BASE address for all 32-bit architectures, based on the GUEST_ADDR_MAX constant. Additionally modify the elf loader to load dynamic pie executables at around: ~ 0x5500000000 for 64-bit guest binaries on 64-bit host, - 0x00300000 for 32-bit guest binaries on 64-bit host, and - 0x00000000 for 32-bit guest binaries on 32-bit host. With this patch the Thread Sanitizer (TSan) application will work again, as in commit aab613fb9597 ("linux-user: Update TASK_UNMAPPED_BASE for aarch64"). Signed-off-by: Helge Deller <deller@gmx.de> --- linux-user/elfload.c | 6 ++++-- linux-user/loader.h | 12 ++++++++++++ linux-user/mmap.c | 35 ++++++++++++++++++----------------- 3 files changed, 34 insertions(+), 19 deletions(-) -- 2.41.0