From: Varad Gautam <varad.gautam@suse.com>
To: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Cc: pbonzini@redhat.com, drjones@redhat.com, jroedel@suse.de,
bp@suse.de, thomas.lendacky@amd.com, brijesh.singh@amd.com,
varad.gautam@suse.com
Subject: [kvm-unit-tests PATCH 4/6] x86: efi_main: Self-relocate ELF .dynamic addresses
Date: Fri, 2 Jul 2021 13:48:18 +0200 [thread overview]
Message-ID: <20210702114820.16712-5-varad.gautam@suse.com> (raw)
In-Reply-To: <20210702114820.16712-1-varad.gautam@suse.com>
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 <varad.gautam@suse.com>
---
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 <alloc_phys.h>
#include <linux/uefi.h>
+#include <elf.h>
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
next prev parent reply other threads:[~2021-07-02 11:48 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-02 11:48 [kvm-unit-tests PATCH 0/6] Initial x86_64 UEFI support Varad Gautam
2021-07-02 11:48 ` [kvm-unit-tests PATCH 1/6] x86: Build tests as PE objects for the EFI loader Varad Gautam
2021-07-02 11:48 ` [kvm-unit-tests PATCH 2/6] x86: Call efi_main from _efi_pe_entry Varad Gautam
2021-07-02 11:48 ` [kvm-unit-tests PATCH 3/6] x86: efi_main: Get EFI memory map and exit boot services Varad Gautam
2021-07-02 11:48 ` Varad Gautam [this message]
2021-07-02 11:48 ` [kvm-unit-tests PATCH 5/6] cstart64.S: x86_64 bootstrapping after exiting EFI Varad Gautam
2021-07-02 11:48 ` [kvm-unit-tests PATCH 6/6] x86: Disable some breaking tests for EFI and modify vmexit test Varad Gautam
2021-07-12 16:29 ` [kvm-unit-tests PATCH 0/6] Initial x86_64 UEFI support Andrew Jones
2021-08-13 18:44 ` Marc Orr
2021-08-16 7:26 ` Andrew Jones
2021-08-17 3:41 ` Marc Orr
2021-08-17 10:49 ` Joerg Roedel
2021-08-18 1:52 ` Marc Orr
2021-08-18 8:38 ` Varad Gautam
2021-08-19 1:32 ` Marc Orr
2021-08-19 1:42 ` Nadav Amit
2021-08-19 1:54 ` Zixuan Wang
2021-08-19 11:36 ` Varad Gautam
2021-08-20 17:29 ` Marc Orr
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