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([2602:47:d483:7301:a064:e3f9:a812:973b]) by smtp.gmail.com with ESMTPSA id g14-20020a170902868e00b001bc2831e1a9sm13446584plo.90.2023.08.16.11.03.44 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Aug 2023 11:03:45 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH v4 07/18] linux-user: Load vdso image if available Date: Wed, 16 Aug 2023 11:03:27 -0700 Message-Id: <20230816180338.572576-8-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230816180338.572576-1-richard.henderson@linaro.org> References: <20230816180338.572576-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::629; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x629.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 The vdso image will be pre-processed into a C data array, with a simple list of relocations to perform, and identifying the location of signal trampolines. Signed-off-by: Richard Henderson --- linux-user/elfload.c | 87 +++++++++++++++++++++++++++++++++++++++----- 1 file changed, 78 insertions(+), 9 deletions(-) diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 19d3cac039..f94963638a 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -33,6 +33,19 @@ #undef ELF_ARCH #endif +#ifndef TARGET_ARCH_HAS_SIGTRAMP_PAGE +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0 +#endif + +typedef struct { + const uint8_t *image; + const uint32_t *relocs; + unsigned image_size; + unsigned reloc_count; + unsigned sigreturn_ofs; + unsigned rt_sigreturn_ofs; +} VdsoImageInfo; + #define ELF_OSABI ELFOSABI_SYSV /* from personality.h */ @@ -2291,7 +2304,8 @@ static abi_ulong loader_build_fdpic_loadmap(struct image_info *info, abi_ulong s static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc, struct elfhdr *exec, struct image_info *info, - struct image_info *interp_info) + struct image_info *interp_info, + struct image_info *vdso_info) { abi_ulong sp; abi_ulong u_argc, u_argv, u_envp, u_auxv; @@ -2379,10 +2393,15 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc, } size = (DLINFO_ITEMS + 1) * 2; - if (k_base_platform) + if (k_base_platform) { size += 2; - if (k_platform) + } + if (k_platform) { size += 2; + } + if (vdso_info) { + size += 2; + } #ifdef DLINFO_ARCH_ITEMS size += DLINFO_ARCH_ITEMS * 2; #endif @@ -2464,6 +2483,9 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc, if (u_platform) { NEW_AUX_ENT(AT_PLATFORM, u_platform); } + if (vdso_info) { + NEW_AUX_ENT(AT_SYSINFO_EHDR, vdso_info->load_addr); + } NEW_AUX_ENT (AT_NULL, 0); #undef NEW_AUX_ENT @@ -3341,6 +3363,49 @@ static void load_elf_interp(const char *filename, struct image_info *info, load_elf_image(filename, &src, info, &ehdr, NULL); } +#ifndef vdso_image_info +#define vdso_image_info() NULL +#endif + +static void load_elf_vdso(struct image_info *info, const VdsoImageInfo *vdso) +{ + ImageSource src; + struct elfhdr ehdr; + abi_ulong load_bias, load_addr; + + src.fd = -1; + src.cache = vdso->image; + src.cache_size = vdso->image_size; + + load_elf_image("", &src, info, &ehdr, NULL); + load_addr = info->load_addr; + load_bias = info->load_bias; + + /* + * We need to relocate the VDSO image. The one built into the kernel + * is built for a fixed address. The one built for QEMU is not, since + * that requires close control of the guest address space. + * We pre-processed the image to locate all of the addresses that need + * to be updated. + */ + for (unsigned i = 0, n = vdso->reloc_count; i < n; i++) { + abi_ulong *addr = g2h_untagged(load_addr + vdso->relocs[i]); + *addr = tswapal(tswapal(*addr) + load_bias); + } + + /* Install signal trampolines, if present. */ + if (vdso->sigreturn_ofs) { + default_sigreturn = load_addr + vdso->sigreturn_ofs; + } + if (vdso->rt_sigreturn_ofs) { + default_rt_sigreturn = load_addr + vdso->rt_sigreturn_ofs; + } + + /* Remove write from VDSO segment. */ + target_mprotect(info->start_data, info->end_data - info->start_data, + PROT_READ | PROT_EXEC); +} + static int symfind(const void *s0, const void *s1) { struct elf_sym *sym = (struct elf_sym *)s1; @@ -3546,7 +3611,7 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info) * and let elf_load_image do any swapping that may be required. */ struct elfhdr ehdr; - struct image_info interp_info; + struct image_info interp_info, vdso_info; char *elf_interpreter = NULL; char *scratch; @@ -3629,10 +3694,13 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info) } /* - * TODO: load a vdso, which would also contain the signal trampolines. - * Otherwise, allocate a private page to hold them. + * Load a vdso if available, which will amongst other things contain the + * signal trampolines. Otherwise, allocate a separate page for them. */ - if (TARGET_ARCH_HAS_SIGTRAMP_PAGE) { + const VdsoImageInfo *vdso = vdso_image_info(); + if (vdso) { + load_elf_vdso(&vdso_info, vdso); + } else if (TARGET_ARCH_HAS_SIGTRAMP_PAGE) { abi_long tramp_page = target_mmap(0, TARGET_PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); @@ -3644,8 +3712,9 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info) target_mprotect(tramp_page, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC); } - bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, &ehdr, - info, (elf_interpreter ? &interp_info : NULL)); + bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, &ehdr, info, + elf_interpreter ? &interp_info : NULL, + vdso ? &vdso_info : NULL); info->start_stack = bprm->p; /* If we have an interpreter, set that as the program's entry point.