Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/55448 )
Change subject: treewide: Disable R_AMD64_32S relocation support ......................................................................
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 patrick.rudolph@9elements.com Reviewed-on: https://review.coreboot.org/c/coreboot/+/55448 Tested-by: build bot (Jenkins) no-reply@coreboot.org Reviewed-by: Arthur Heymans arthur@aheymans.xyz --- M src/arch/x86/c_start.S M src/arch/x86/exit_car.S M src/arch/x86/gdt_init.S M src/cpu/x86/lapic/secondary.S M src/cpu/x86/sipi_vector.S M src/cpu/x86/smm/smm_stub.S M util/cbfstool/rmodule.c 7 files changed, 43 insertions(+), 26 deletions(-)
Approvals: build bot (Jenkins): Verified Arthur Heymans: Looks good to me, approved
diff --git a/src/arch/x86/c_start.S b/src/arch/x86/c_start.S index f55ab6e..b7ffddc 100644 --- a/src/arch/x86/c_start.S +++ b/src/arch/x86/c_start.S @@ -32,8 +32,11 @@ .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 @@ 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 @@ * 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 @@ 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 fae7899..d1b1a53 100644 --- a/src/arch/x86/exit_car.S +++ b/src/arch/x86/exit_car.S @@ -49,7 +49,8 @@ #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 @@ 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 @@ 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 f33a151..30b3965 100644 --- a/src/arch/x86/gdt_init.S +++ b/src/arch/x86/gdt_init.S @@ -23,18 +23,6 @@ .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 073e6b4..d36bc9a 100644 --- a/src/cpu/x86/lapic/secondary.S +++ b/src/cpu/x86/lapic/secondary.S @@ -61,9 +61,11 @@ #if ENV_X86_64 /* entry64.inc preserves ebx. */ #include <cpu/x86/64bit/entry64.inc> - 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 f9b2957..d8156b8 100644 --- a/src/cpu/x86/sipi_vector.S +++ b/src/cpu/x86/sipi_vector.S @@ -220,7 +220,7 @@
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 0c690da..07be047 100644 --- a/src/cpu/x86/smm/smm_stub.S +++ b/src/cpu/x86/smm/smm_stub.S @@ -210,7 +210,7 @@
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 4ac2951..ce00510 100644 --- a/util/cbfstool/rmodule.c +++ b/util/cbfstool/rmodule.c @@ -38,10 +38,16 @@
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 @@
/* Only emit absolute relocations */ return (type == R_AMD64_64 || - type == R_AMD64_32S || type == R_AMD64_32); }
@@ -182,6 +187,10 @@ 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; }