From d023909b0112889941c1470cd125b1903572ba3b Mon Sep 17 00:00:00 2001 From: Patrick Rudolph Date: Fri, 11 Jun 2021 21:24:10 +0200 Subject: [PATCH] treewide: Disable R_AMD64_32S relocation support This fixes a hard to debug hang that could occur in any stage, but in the end it follows simple rules and is easy to fix. In long mode the 32bit displacement addressing used on 'mov' and 'lea' instructions is sign-extended. Those instructions can be found using readelf on the stage and searching for relocation type R_X86_64_32S. The sign extension is no issue when either running in protected mode or the code module and thus the address is below 2GiB. If the address is greater than 2GiB, as usually the case for code in TSEG, the higher address bits [64:32] are all set to 1 and the effective address is pointing to memory not paged. Accessing this memory will cause a page fault, which isn't handled either. To prevent such problems - disable R_AMD64_32S relocations in rmodtool - add comment explaining why it's not allowed - use the pseudo op movabs, which doesn't use 32bit displacement addressing - Print a useful error message if such a reloc is present in the code Fixes a crash in TSEG and when in long mode seen on Intel Sandybridge. Change-Id: Ia5f5a9cde7c325f67b12e3a8e9a76283cc3870a3 Signed-off-by: Patrick Rudolph Reviewed-on: https://review.coreboot.org/c/coreboot/+/55448 Tested-by: build bot (Jenkins) Reviewed-by: Arthur Heymans --- src/arch/x86/c_start.S | 13 +++++++++---- src/arch/x86/exit_car.S | 19 ++++++++++++++++--- src/arch/x86/gdt_init.S | 12 ------------ src/cpu/x86/lapic/secondary.S | 6 ++++-- src/cpu/x86/sipi_vector.S | 2 +- src/cpu/x86/smm/smm_stub.S | 2 +- util/cbfstool/rmodule.c | 15 ++++++++++++--- 7 files changed, 43 insertions(+), 26 deletions(-) diff --git a/src/arch/x86/c_start.S b/src/arch/x86/c_start.S index f55ab6e06e..b7ffddc385 100644 --- a/src/arch/x86/c_start.S +++ b/src/arch/x86/c_start.S @@ -32,8 +32,11 @@ thread_stacks: .globl _start _start: cli +#ifdef __x86_64__ + movabs $gdtaddr, %rax + lgdt (%rax) +#else lgdt %cs:gdtaddr -#ifndef __x86_64__ ljmp $RAM_CODE_SEG, $1f #endif 1: movl $RAM_DATA_SEG, %eax @@ -52,11 +55,14 @@ _start: cld #ifdef __x86_64__ - mov %rdi, _cbmem_top_ptr + mov %rdi, %rax + movabs %rax, _cbmem_top_ptr + movabs $_stack, %rdi #else /* The return argument is at 0(%esp), the calling argument at 4(%esp) */ movl 4(%esp), %eax movl %eax, _cbmem_top_ptr + leal _stack, %edi #endif /** poison the stack. Code should not count on the @@ -64,7 +70,6 @@ _start: * recently uncovered a bug in the broadcast SIPI * code. */ - leal _stack, %edi movl $_estack, %ecx subl %edi, %ecx shrl $2, %ecx /* it is 32 bit aligned, right? */ @@ -226,7 +231,7 @@ SetCodeSelector: push %rsp pushfq push %rcx # cx is code segment selector from caller - mov $setCodeSelectorLongJump, %rax + movabs $setCodeSelectorLongJump, %rax push %rax # the iret will continue at next instruction, with the new cs value diff --git a/src/arch/x86/exit_car.S b/src/arch/x86/exit_car.S index fae7899e17..d1b1a537fe 100644 --- a/src/arch/x86/exit_car.S +++ b/src/arch/x86/exit_car.S @@ -49,7 +49,8 @@ _start: #endif #ifdef __x86_64__ - mov %rdi, _cbmem_top_ptr + mov %rdi, %rax + movabs %rax, _cbmem_top_ptr #else /* The return argument is at 0(%esp), the calling argument at 4(%esp) */ movl 4(%esp), %eax @@ -60,7 +61,12 @@ _start: cpuid btl $CPUID_FEATURE_CLFLUSH_BIT, %edx jnc skip_clflush +#ifdef __x86_64__ + movabs _cbmem_top_ptr, %rax + clflush (%rax) +#else clflush _cbmem_top_ptr +#endif skip_clflush: /* chipset_teardown_car() is expected to disable cache-as-ram. */ @@ -71,17 +77,24 @@ skip_clflush: mov %cr0, %rax and $(~(CR0_CD | CR0_NW)), %eax mov %rax, %cr0 + + /* Ensure cache is clean. */ + invd + + /* Set up new stack. */ + movabs post_car_stack_top, %rax + mov %rax, %rsp #else mov %cr0, %eax and $(~(CR0_CD | CR0_NW)), %eax mov %eax, %cr0 -#endif + /* Ensure cache is clean. */ invd /* Set up new stack. */ mov post_car_stack_top, %esp - +#endif /* * Honor variable MTRR information pushed on the stack with the * following layout: diff --git a/src/arch/x86/gdt_init.S b/src/arch/x86/gdt_init.S index f33a1517d8..30b39653c9 100644 --- a/src/arch/x86/gdt_init.S +++ b/src/arch/x86/gdt_init.S @@ -23,18 +23,6 @@ gdtptr: .section .init._gdt64_, "ax", @progbits .globl gdt_init64 gdt_init64: - /* Workaround a bug in the assembler. - * The following code doesn't work: - * lgdt gdtptr64 - * - * The assembler tries to save memory by using 32bit displacement addressing mode. - * Displacements are using signed integers. - * This is fine in protected mode, as the negative address points to the correct - * address > 2GiB, but in long mode this doesn't work at all. - * Tests showed that QEMU can gracefully handle it, but real CPUs can't. - * - * Use the movabs pseudo instruction to force using a 64bit absolute address. - */ movabs $gdtptr64, %rax lgdt (%rax) ret diff --git a/src/cpu/x86/lapic/secondary.S b/src/cpu/x86/lapic/secondary.S index 073e6b485b..d36bc9a645 100644 --- a/src/cpu/x86/lapic/secondary.S +++ b/src/cpu/x86/lapic/secondary.S @@ -61,9 +61,11 @@ __ap_protected_start: #if ENV_X86_64 /* entry64.inc preserves ebx. */ #include - mov secondary_stack, %rsp + movabs secondary_stack, %rax + mov %rax, %rsp andl $0xfffffff0, %esp - mov secondary_cpu_index, %rdi + movabs secondary_cpu_index, %rax + mov %rax, %rdi #else /* Set the stack pointer, and flag that we are done */ xorl %eax, %eax diff --git a/src/cpu/x86/sipi_vector.S b/src/cpu/x86/sipi_vector.S index f9b29576bd..d8156b88a8 100644 --- a/src/cpu/x86/sipi_vector.S +++ b/src/cpu/x86/sipi_vector.S @@ -220,7 +220,7 @@ load_msr: mov %rsi, %rdi /* cpu_num */ - movl c_handler, %eax + movabs c_handler, %eax call *%rax #else /* c_handler(cpu_num), preserve proper stack alignment */ diff --git a/src/cpu/x86/smm/smm_stub.S b/src/cpu/x86/smm/smm_stub.S index 0c690da986..07be047a36 100644 --- a/src/cpu/x86/smm/smm_stub.S +++ b/src/cpu/x86/smm/smm_stub.S @@ -210,7 +210,7 @@ apicid_end: mov %rsp, %rdi /* *arg */ - movl c_handler, %eax + movabs c_handler, %eax call *%rax /* diff --git a/util/cbfstool/rmodule.c b/util/cbfstool/rmodule.c index 4ac2951f72..ce005108ed 100644 --- a/util/cbfstool/rmodule.c +++ b/util/cbfstool/rmodule.c @@ -38,10 +38,16 @@ static int valid_reloc_amd64(Elf64_Rela *rel) type = ELF64_R_TYPE(rel->r_info); - /* Only these 6 relocations are expected to be found. */ + /* + * Relocation R_AMD64_32S is not allowed. It can only be safely used in protected mode, + * and when the address pointed to is below 2 GiB in long mode. + * Using it in assembly operations will break compilation with error: + * E: Invalid reloc type: 11 + */ + + /* Only these 5 relocations are expected to be found. */ return (type == R_AMD64_64 || type == R_AMD64_PC64 || - type == R_AMD64_32S || type == R_AMD64_32 || type == R_AMD64_PC32 || /* @@ -60,7 +66,6 @@ static int should_emit_amd64(Elf64_Rela *rel) /* Only emit absolute relocations */ return (type == R_AMD64_64 || - type == R_AMD64_32S || type == R_AMD64_32); } @@ -182,6 +187,10 @@ static int for_each_reloc(struct rmod_context *ctx, struct reloc_filter *f, if (!ctx->ops->valid_type(r)) { ERROR("Invalid reloc type: %u\n", (unsigned int)ELF64_R_TYPE(r->r_info)); + if ((ctx->ops->arch == EM_X86_64) && + (ELF64_R_TYPE(r->r_info) == R_AMD64_32S)) + ERROR("Illegal use of 32bit sign extended addressing at offset 0x%x\n", + (unsigned int)r->r_offset); return -1; }