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Thu, 27 Jul 2023 09:06:02 +0200 From: Helge Deller To: qemu-devel@nongnu.org Cc: Richard Henderson , Laurent Vivier , Paolo Bonzini , Helge Deller Subject: [PATCH v4 2/3] linux-user: Optimize memory layout for static and dynamic executables Date: Thu, 27 Jul 2023 09:06:00 +0200 Message-ID: <20230727070601.31383-3-deller@gmx.de> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230727070601.31383-1-deller@gmx.de> References: <20230727070601.31383-1-deller@gmx.de> MIME-Version: 1.0 X-Provags-ID: V03:K1:JFHab12JDvxz9EAnM3azlGmgUCzavKlaFT0A9HWdYVaWOPGQw2J 3vqVv9bmZkZq5Id/iIvjr8Gq8Ujeq5BDTQxGIMo+aCvgHSdAeDPO8oarVEptLwgXlZ1ohkB 8yAJvRZOXiuidCkow6WC9s1g9U7yo/c9iAP8LXMqkj0QbScJYEW56SppEwuJUR488fnpih7 VOd9zTRZjadYePXpNWBkw== UI-OutboundReport: notjunk:1;M01:P0:/0DezqE242c=;83Z2WDH6FpSeLtzz+8NOijP/ikC PvwveM1OpI9aXm1K4E4i1UmSBBxyz78HgTTGcab3+aW3TJV9iqOz8SNpmriEmhR47PZWpt7yY /dKtnupgVhxE06e+RWO8pM/les9IOCvTKLNtW0EJ5oFFedJt/Cbo2hlWpj60dfiFFY6qKkxwI UO/zcTn/Dg/tSKnosOvoMekPMbyIXVPp6xr1BUS8pBo7MK2EPNUWL4Ph3zSqSd3ydh81D7yUl w3EJWl5w164/JxFthzBI2N1oN43gJL9LkqQM2+EohwGV4dFCLPJ7VzbQRpSPrHC/d2XF3QwYj 7ywgHiIob+QJHkrzc3bAwonW/s15kAraqL7GUBxtyWf8xY0RS3Dh2DOl70qXrF3drPs73/o43 1xJv9vR4u1QpAWScjOEGGtFpwyCULFiCTS6dQ3CXZc4isNWIzhXVB3FOqvsp8N2ppx0+zs0YE oPJdP5ZK2kiulN4kEjnRtnuepsPkDjIqG0xN4RRsQbKYoa+h58F7P3UoSmDY+KKKDlsrIIvc4 EFHR13IIUDDwlbh8eOoYywBrvmLPWoMBa14ozdPfr5ZegSUa6R4Tg7SsKWcdaPfeFV2ILX+gz QvVtsvvo+yUbn5U1sT3a1mRGlDDc5GxYRsInhhPhi7xiBl8UOOh1cUvsEgt7+npQLlNHWPEYC VNqhP/RNq74nN9n3u/Z9qZwD1WX4ew6lrbYJVKwAWVuO7SXNwtmtTVY8EwDboEoT/w6tTJG1Y 4HG5my70ppFaV2Sr5kuWRxFmwkPerOnb2B0UkaRvApyxsqDDLEpMHBjHwkDaMeJOhaXpKEMJh bQfpE7fZSbkTPJX0hVodpBqrzgNjIca+VMZ3d+V7cFOkraMjGYtkiHGU/VTLuh7fKJ1PDywdM Sj6UVkl8WMo53sHRVobRC/b4543C7IejI0+syttA86DlGkCvze8/3Un7jdQ7wwF0K/BdOTx7c uiqSn64ng5CkJRZ/Yaud6SWCN6U= Received-SPF: pass client-ip=212.227.17.21; envelope-from=deller@gmx.de; helo=mout.gmx.net X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Organize the emulated memory layout in a way which leaves as much memory as possible for heap for the application. This patch tries to optize the memory layout by loading pie executables into lower memory and shared libs into higher memory (at TASK_UNMAPPED_BASE). This leaves a bigger memory area usable for heap space which will be located directly after the executable. Up to now, pie executable and shared libs were loaded directly behind each other in the area at TASK_UNMAPPED_BASE, which leaves very little space for heap. I tested this change on arm64, armhf and hppa (all in chroot on x86-64), and with a static armhf binary (which is broken without this patch). This patch temporarily breaks the Thread Sanitizer (TSan) application which expects specific boundary definitions for memory mappings on different platforms [1], see commit aab613fb9597 ("linux-user: Update TASK_UNMAPPED_BASE for aarch64") for aarch64. The follow-up patch fixes it again. [1] https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/tsan/rtl/tsan_platform.h Signed-off-by: Helge Deller --- linux-user/elfload.c | 55 +++++++++++++------------------------------- linux-user/mmap.c | 8 ++++--- 2 files changed, 21 insertions(+), 42 deletions(-) -- 2.41.0 diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 861ec07abc..47a118e430 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -3023,6 +3023,7 @@ static void load_elf_image(const char *image_name, int image_fd, abi_ulong load_addr, load_bias, loaddr, hiaddr, error; int i, retval, prot_exec; Error *err = NULL; + bool is_main_executable; /* First of all, some simple consistency checks */ if (!elf_check_ident(ehdr)) { @@ -3106,28 +3107,8 @@ static void load_elf_image(const char *image_name, int image_fd, } } - if (pinterp_name != NULL) { - /* - * This is the main executable. - * - * Reserve extra space for brk. - * We hold on to this space while placing the interpreter - * and the stack, lest they be placed immediately after - * the data segment and block allocation from the brk. - * - * 16MB is chosen as "large enough" without being so large as - * to allow the result to not fit with a 32-bit guest on a - * 32-bit host. However some 64 bit guests (e.g. s390x) - * attempt to place their heap further ahead and currently - * nothing stops them smashing into QEMUs address space. - */ -#if TARGET_LONG_BITS == 64 - info->reserve_brk = 32 * MiB; -#else - info->reserve_brk = 16 * MiB; -#endif - hiaddr += info->reserve_brk; - + is_main_executable = (pinterp_name != NULL); + if (is_main_executable) { if (ehdr->e_type == ET_EXEC) { /* * Make sure that the low address does not conflict with @@ -3136,7 +3117,7 @@ static void load_elf_image(const char *image_name, int image_fd, probe_guest_base(image_name, loaddr, hiaddr); } else { /* - * The binary is dynamic, but we still need to + * The binary is dynamic (pie-executabe), but we still need to * select guest_base. In this case we pass a size. */ probe_guest_base(image_name, 0, hiaddr - loaddr); @@ -3159,7 +3140,7 @@ static void load_elf_image(const char *image_name, int image_fd, */ load_addr = target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, PROT_NONE, MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | - (ehdr->e_type == ET_EXEC ? MAP_FIXED : 0), + (is_main_executable ? MAP_FIXED : 0), -1, 0); if (load_addr == -1) { goto exit_mmap; @@ -3194,7 +3175,8 @@ static void load_elf_image(const char *image_name, int image_fd, info->end_code = 0; info->start_data = -1; info->end_data = 0; - info->brk = 0; + /* possible start for brk is behind all sections of this ELF file. */ + info->brk = TARGET_PAGE_ALIGN(hiaddr); info->elf_flags = ehdr->e_flags; prot_exec = PROT_EXEC; @@ -3288,9 +3270,6 @@ static void load_elf_image(const char *image_name, int image_fd, info->end_data = vaddr_ef; } } - if (vaddr_em > info->brk) { - info->brk = vaddr_em; - } #ifdef TARGET_MIPS } else if (eppnt->p_type == PT_MIPS_ABIFLAGS) { Mips_elf_abiflags_v0 abiflags; @@ -3618,6 +3597,15 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info) if (elf_interpreter) { load_elf_interp(elf_interpreter, &interp_info, bprm->buf); + /* + * Use brk address of interpreter if it was loaded above the + * executable and leaves less than 16 MB for heap. + * This happens e.g. with static binaries on armhf. + */ + if (interp_info.brk > info->brk && + interp_info.load_bias - info->brk < 16 * MiB) { + info->brk = interp_info.brk; + } /* If the program interpreter is one of these two, then assume an iBCS2 image. Otherwise assume a native linux image. */ @@ -3672,17 +3660,6 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info) bprm->core_dump = &elf_core_dump; #endif - /* - * If we reserved extra space for brk, release it now. - * The implementation of do_brk in syscalls.c expects to be able - * to mmap pages in this space. - */ - if (info->reserve_brk) { - abi_ulong start_brk = HOST_PAGE_ALIGN(info->brk); - abi_ulong end_brk = HOST_PAGE_ALIGN(info->brk + info->reserve_brk); - target_munmap(start_brk, end_brk - start_brk); - } - return 0; } diff --git a/linux-user/mmap.c b/linux-user/mmap.c index a5dfb56545..848d2fd4bb 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -299,14 +299,16 @@ static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last, #ifdef TARGET_AARCH64 # define TASK_UNMAPPED_BASE 0x5500000000 #else -# define TASK_UNMAPPED_BASE (1ul << 38) +# define TASK_UNMAPPED_BASE 0x4000000000 #endif -#else +#elif HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 32 #ifdef TARGET_HPPA # define TASK_UNMAPPED_BASE 0xfa000000 #else -# define TASK_UNMAPPED_BASE 0x40000000 +# 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;