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[95.90.92.25]) by smtp.gmail.com with ESMTPSA id w11sm2682859wrr.48.2021.08.19.04.35.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Aug 2021 04:35:14 -0700 (PDT) From: Varad Gautam X-Google-Original-From: Varad Gautam To: Zixuan Wang , Nadav Amit , Marc Orr , Joerg Roedel , kvm list , Linux Virtualization , Paolo Bonzini , Andrew Jones , bp@suse.de, Thomas.Lendacky@amd.com, brijesh.singh@amd.com, Hyunwook Baek , Erdem Aktas , Tom Roeder Cc: Varad Gautam Subject: [kvm-unit-tests PATCH v2 4/6] x86: efi_main: Self-relocate ELF .dynamic addresses Date: Thu, 19 Aug 2021 13:33:58 +0200 Message-Id: <20210819113400.26516-5-varad.gautam@suse.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210819113400.26516-1-varad.gautam@suse.com> References: <20210819113400.26516-1-varad.gautam@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org EFI expects a relocatable PE, and the loader will patch in the relocations from the COFF. Since we are wrapping an ELF into a PE here, the EFI loader will not handle ELF relocations, and we need to patch the ELF .dynamic section manually on early boot. Signed-off-by: Varad Gautam --- x86/efi_main.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/x86/efi_main.c b/x86/efi_main.c index 237d4e7..be3f9ab 100644 --- a/x86/efi_main.c +++ b/x86/efi_main.c @@ -1,9 +1,13 @@ #include #include +#include unsigned long __efiapi efi_main(efi_handle_t handle, efi_system_table_t *sys_tab); efi_system_table_t *efi_system_table = NULL; +extern char ImageBase; +extern char _DYNAMIC; + static void efi_free_pool(void *ptr) { efi_bs_call(free_pool, ptr); @@ -93,11 +97,70 @@ static efi_status_t exit_efi(void *handle) return EFI_SUCCESS; } +static efi_status_t elf_reloc(unsigned long image_base, unsigned long dynamic) +{ + long relsz = 0, relent = 0; + Elf64_Rel *rel = 0; + Elf64_Dyn *dyn = (Elf64_Dyn *) dynamic; + unsigned long *addr; + int i; + + for (i = 0; dyn[i].d_tag != DT_NULL; i++) { + switch (dyn[i].d_tag) { + case DT_RELA: + rel = (Elf64_Rel *) + ((unsigned long) dyn[i].d_un.d_ptr + image_base); + break; + case DT_RELASZ: + relsz = dyn[i].d_un.d_val; + break; + case DT_RELAENT: + relent = dyn[i].d_un.d_val; + break; + default: + break; + } + } + + if (!rel && relent == 0) + return EFI_SUCCESS; + + if (!rel || relent == 0) + return EFI_LOAD_ERROR; + + while (relsz > 0) { + /* apply the relocs */ + switch (ELF64_R_TYPE (rel->r_info)) { + case R_X86_64_NONE: + break; + case R_X86_64_RELATIVE: + addr = (unsigned long *) (image_base + rel->r_offset); + *addr += image_base; + break; + default: + break; + } + rel = (Elf64_Rel *) ((char *) rel + relent); + relsz -= relent; + } + return EFI_SUCCESS; +} + unsigned long __efiapi efi_main(efi_handle_t handle, efi_system_table_t *sys_tab) { + unsigned long image_base, dyn; efi_system_table = sys_tab; exit_efi(handle); + image_base = (unsigned long) &ImageBase; + dyn = image_base + (unsigned long) &_DYNAMIC; + + /* The EFI loader does not handle ELF relocations, so fixup + * .dynamic addresses before proceeding any further. */ + elf_reloc(image_base, dyn); + + start64(); + return 0; } -- 2.30.2