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fb799447ae
Mark reported that the ORC unwinder incorrectly marks an unwind as
reliable when the unwind terminates prematurely in the dark corners of
return_to_handler() due to lack of information about the next frame.
The problem is UNWIND_HINT_EMPTY is used in two different situations:
1) The end of the kernel stack unwind before hitting user entry, boot
code, or fork entry
2) A blind spot in ORC coverage where the unwinder has to bail due to
lack of information about the next frame
The ORC unwinder has no way to tell the difference between the two.
When it encounters an undefined stack state with 'end=1', it blindly
marks the stack reliable, which can break the livepatch consistency
model.
Fix it by splitting UNWIND_HINT_EMPTY into UNWIND_HINT_UNDEFINED and
UNWIND_HINT_END_OF_STACK.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/fd6212c8b450d3564b855e1cb48404d6277b4d9f.1677683419.git.jpoimboe@kernel.org
120 lines
3.3 KiB
ArmAsm
120 lines
3.3 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/* Xen-specific pieces of head.S, intended to be included in the right
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place in head.S */
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#ifdef CONFIG_XEN
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#include <linux/elfnote.h>
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#include <linux/init.h>
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#include <asm/boot.h>
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#include <asm/asm.h>
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#include <asm/msr.h>
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#include <asm/page_types.h>
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#include <asm/percpu.h>
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#include <asm/unwind_hints.h>
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#include <xen/interface/elfnote.h>
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#include <xen/interface/features.h>
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#include <xen/interface/xen.h>
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#include <xen/interface/xen-mca.h>
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#include <asm/xen/interface.h>
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.pushsection .noinstr.text, "ax"
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.balign PAGE_SIZE
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SYM_CODE_START(hypercall_page)
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.rept (PAGE_SIZE / 32)
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UNWIND_HINT_FUNC
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ANNOTATE_NOENDBR
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ANNOTATE_UNRET_SAFE
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ret
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/*
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* Xen will write the hypercall page, and sort out ENDBR.
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*/
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.skip 31, 0xcc
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.endr
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#define HYPERCALL(n) \
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.equ xen_hypercall_##n, hypercall_page + __HYPERVISOR_##n * 32; \
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.type xen_hypercall_##n, @function; .size xen_hypercall_##n, 32
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#include <asm/xen-hypercalls.h>
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#undef HYPERCALL
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SYM_CODE_END(hypercall_page)
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.popsection
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#ifdef CONFIG_XEN_PV
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__INIT
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SYM_CODE_START(startup_xen)
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UNWIND_HINT_END_OF_STACK
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ANNOTATE_NOENDBR
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cld
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mov initial_stack(%rip), %rsp
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/* Set up %gs.
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*
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* The base of %gs always points to fixed_percpu_data. If the
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* stack protector canary is enabled, it is located at %gs:40.
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* Note that, on SMP, the boot cpu uses init data section until
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* the per cpu areas are set up.
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*/
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movl $MSR_GS_BASE,%ecx
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movq $INIT_PER_CPU_VAR(fixed_percpu_data),%rax
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cdq
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wrmsr
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mov %rsi, %rdi
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call xen_start_kernel
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SYM_CODE_END(startup_xen)
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__FINIT
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#ifdef CONFIG_XEN_PV_SMP
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.pushsection .text
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SYM_CODE_START(asm_cpu_bringup_and_idle)
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UNWIND_HINT_END_OF_STACK
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ENDBR
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call cpu_bringup_and_idle
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SYM_CODE_END(asm_cpu_bringup_and_idle)
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SYM_CODE_START(xen_cpu_bringup_again)
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UNWIND_HINT_FUNC
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mov %rdi, %rsp
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UNWIND_HINT_REGS
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call cpu_bringup_and_idle
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SYM_CODE_END(xen_cpu_bringup_again)
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.popsection
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#endif
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#endif
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ELFNOTE(Xen, XEN_ELFNOTE_GUEST_OS, .asciz "linux")
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ELFNOTE(Xen, XEN_ELFNOTE_GUEST_VERSION, .asciz "2.6")
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ELFNOTE(Xen, XEN_ELFNOTE_XEN_VERSION, .asciz "xen-3.0")
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#ifdef CONFIG_X86_32
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ELFNOTE(Xen, XEN_ELFNOTE_VIRT_BASE, _ASM_PTR __PAGE_OFFSET)
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#else
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ELFNOTE(Xen, XEN_ELFNOTE_VIRT_BASE, _ASM_PTR __START_KERNEL_map)
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/* Map the p2m table to a 512GB-aligned user address. */
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ELFNOTE(Xen, XEN_ELFNOTE_INIT_P2M, .quad (PUD_SIZE * PTRS_PER_PUD))
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#endif
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#ifdef CONFIG_XEN_PV
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ELFNOTE(Xen, XEN_ELFNOTE_ENTRY, _ASM_PTR startup_xen)
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#endif
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ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, _ASM_PTR hypercall_page)
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ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,
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.ascii "!writable_page_tables|pae_pgdir_above_4gb")
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ELFNOTE(Xen, XEN_ELFNOTE_SUPPORTED_FEATURES,
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.long (1 << XENFEAT_writable_page_tables) | \
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(1 << XENFEAT_dom0) | \
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(1 << XENFEAT_linux_rsdp_unrestricted))
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ELFNOTE(Xen, XEN_ELFNOTE_PAE_MODE, .asciz "yes")
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ELFNOTE(Xen, XEN_ELFNOTE_LOADER, .asciz "generic")
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ELFNOTE(Xen, XEN_ELFNOTE_L1_MFN_VALID,
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.quad _PAGE_PRESENT; .quad _PAGE_PRESENT)
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ELFNOTE(Xen, XEN_ELFNOTE_SUSPEND_CANCEL, .long 1)
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ELFNOTE(Xen, XEN_ELFNOTE_MOD_START_PFN, .long 1)
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ELFNOTE(Xen, XEN_ELFNOTE_HV_START_LOW, _ASM_PTR __HYPERVISOR_VIRT_START)
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ELFNOTE(Xen, XEN_ELFNOTE_PADDR_OFFSET, _ASM_PTR 0)
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#endif /*CONFIG_XEN */
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