arm64: entry: simplify trampoline data page
Get rid of some clunky open coded arithmetic on section addresses, by emitting the trampoline data variables into a separate, dedicated r/o data section, and putting it at the next page boundary. This way, we can access the literals via single LDR instruction. While at it, get rid of other, implicit literals, and use ADRP/ADD or MOVZ/MOVK sequences, as appropriate. Note that the latter are only supported for CONFIG_RELOCATABLE=n (which is usually the case if CONFIG_RANDOMIZE_BASE=n), so update the CPP conditionals to reflect this. Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20220622161010.3845775-1-ardb@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ard Biesheuvel
Will Deacon
parent
47546a1912
commit
1c9a8e8768
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@ -62,10 +62,12 @@ enum fixed_addresses {
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#endif /* CONFIG_ACPI_APEI_GHES */
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#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
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#ifdef CONFIG_RELOCATABLE
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FIX_ENTRY_TRAMP_TEXT4, /* one extra slot for the data page */
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#endif
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FIX_ENTRY_TRAMP_TEXT3,
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FIX_ENTRY_TRAMP_TEXT2,
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FIX_ENTRY_TRAMP_TEXT1,
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FIX_ENTRY_TRAMP_DATA,
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#define TRAMP_VALIAS (__fix_to_virt(FIX_ENTRY_TRAMP_TEXT1))
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#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
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__end_of_permanent_fixed_addresses,
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@ -636,18 +636,28 @@ alternative_else_nop_endif
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*/
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.endm
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.macro tramp_data_page dst
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adr_l \dst, .entry.tramp.text
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sub \dst, \dst, PAGE_SIZE
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.endm
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.macro tramp_data_read_var dst, var
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#ifdef CONFIG_RANDOMIZE_BASE
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tramp_data_page \dst
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add \dst, \dst, #:lo12:__entry_tramp_data_\var
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ldr \dst, [\dst]
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.macro tramp_data_read_var dst, var
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#ifdef CONFIG_RELOCATABLE
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ldr \dst, .L__tramp_data_\var
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.ifndef .L__tramp_data_\var
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.pushsection ".entry.tramp.rodata", "a", %progbits
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.align 3
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.L__tramp_data_\var:
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.quad \var
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.popsection
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.endif
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#else
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ldr \dst, =\var
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/*
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* As !RELOCATABLE implies !RANDOMIZE_BASE the address is always a
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* compile time constant (and hence not secret and not worth hiding).
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*
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* As statically allocated kernel code and data always live in the top
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* 47 bits of the address space we can sign-extend bit 47 and avoid an
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* instruction to load the upper 16 bits (which must be 0xFFFF).
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*/
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movz \dst, :abs_g2_s:\var
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movk \dst, :abs_g1_nc:\var
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movk \dst, :abs_g0_nc:\var
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#endif
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.endm
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@ -695,7 +705,7 @@ alternative_else_nop_endif
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msr vbar_el1, x30
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isb
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.else
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ldr x30, =vectors
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adr_l x30, vectors
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.endif // \kpti == 1
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.if \bhb == BHB_MITIGATION_FW
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@ -764,24 +774,7 @@ SYM_CODE_END(tramp_exit_native)
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SYM_CODE_START(tramp_exit_compat)
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tramp_exit 32
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SYM_CODE_END(tramp_exit_compat)
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.ltorg
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.popsection // .entry.tramp.text
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#ifdef CONFIG_RANDOMIZE_BASE
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.pushsection ".rodata", "a"
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.align PAGE_SHIFT
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SYM_DATA_START(__entry_tramp_data_start)
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__entry_tramp_data_vectors:
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.quad vectors
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#ifdef CONFIG_ARM_SDE_INTERFACE
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__entry_tramp_data___sdei_asm_handler:
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.quad __sdei_asm_handler
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#endif /* CONFIG_ARM_SDE_INTERFACE */
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__entry_tramp_data_this_cpu_vector:
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.quad this_cpu_vector
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SYM_DATA_END(__entry_tramp_data_start)
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.popsection // .rodata
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#endif /* CONFIG_RANDOMIZE_BASE */
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#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
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/*
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@ -932,7 +925,6 @@ NOKPROBE(call_on_irq_stack)
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* This clobbers x4, __sdei_handler() will restore this from firmware's
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* copy.
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*/
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.ltorg
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.pushsection ".entry.tramp.text", "ax"
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SYM_CODE_START(__sdei_asm_entry_trampoline)
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mrs x4, ttbr1_el1
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@ -967,7 +959,6 @@ SYM_CODE_START(__sdei_asm_exit_trampoline)
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1: sdei_handler_exit exit_mode=x2
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SYM_CODE_END(__sdei_asm_exit_trampoline)
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NOKPROBE(__sdei_asm_exit_trampoline)
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.ltorg
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.popsection // .entry.tramp.text
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#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
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@ -115,7 +115,8 @@ jiffies = jiffies_64;
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__entry_tramp_text_start = .; \
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*(.entry.tramp.text) \
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. = ALIGN(PAGE_SIZE); \
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__entry_tramp_text_end = .;
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__entry_tramp_text_end = .; \
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*(.entry.tramp.rodata)
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#else
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#define TRAMP_TEXT
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#endif
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@ -672,13 +672,9 @@ static int __init map_entry_trampoline(void)
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__set_fixmap(FIX_ENTRY_TRAMP_TEXT1 - i,
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pa_start + i * PAGE_SIZE, prot);
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if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
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extern char __entry_tramp_data_start[];
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__set_fixmap(FIX_ENTRY_TRAMP_DATA,
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__pa_symbol(__entry_tramp_data_start),
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PAGE_KERNEL_RO);
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}
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if (IS_ENABLED(CONFIG_RELOCATABLE))
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__set_fixmap(FIX_ENTRY_TRAMP_TEXT1 - i,
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pa_start + i * PAGE_SIZE, PAGE_KERNEL_RO);
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return 0;
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}
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