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From foo@baz Tue Mar 8 08:47:19 PM CET 2022 |
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From: James Morse <james.morse@arm.com> |
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Date: Wed, 24 Nov 2021 11:40:18 +0000 |
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Subject: arm64: entry: Allow tramp_alias to access symbols after the 4K boundary |
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|
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From: James Morse <james.morse@arm.com> |
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|
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commit 6c5bf79b69f911560fbf82214c0971af6e58e682 upstream. |
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|
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Systems using kpti enter and exit the kernel through a trampoline mapping |
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that is always mapped, even when the kernel is not. tramp_valias is a macro |
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to find the address of a symbol in the trampoline mapping. |
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|
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Adding extra sets of vectors will expand the size of the entry.tramp.text |
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section to beyond 4K. tramp_valias will be unable to generate addresses |
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for symbols beyond 4K as it uses the 12 bit immediate of the add |
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instruction. |
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|
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As there are now two registers available when tramp_alias is called, |
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use the extra register to avoid the 4K limit of the 12 bit immediate. |
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|
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Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> |
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Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> |
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Signed-off-by: James Morse <james.morse@arm.com> |
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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--- |
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arch/arm64/kernel/entry.S | 13 ++++++++----- |
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1 file changed, 8 insertions(+), 5 deletions(-) |
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|
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--- a/arch/arm64/kernel/entry.S |
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+++ b/arch/arm64/kernel/entry.S |
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@@ -103,9 +103,12 @@ |
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.org .Lventry_start\@ + 128 // Did we overflow the ventry slot? |
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.endm |
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|
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- .macro tramp_alias, dst, sym |
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+ .macro tramp_alias, dst, sym, tmp |
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mov_q \dst, TRAMP_VALIAS |
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- add \dst, \dst, #(\sym - .entry.tramp.text) |
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+ adr_l \tmp, \sym |
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+ add \dst, \dst, \tmp |
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+ adr_l \tmp, .entry.tramp.text |
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+ sub \dst, \dst, \tmp |
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.endm |
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|
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/* |
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@@ -429,10 +432,10 @@ alternative_else_nop_endif |
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#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 |
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bne 4f |
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msr far_el1, x29 |
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- tramp_alias x30, tramp_exit_native |
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+ tramp_alias x30, tramp_exit_native, x29 |
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br x30 |
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4: |
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- tramp_alias x30, tramp_exit_compat |
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+ tramp_alias x30, tramp_exit_compat, x29 |
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br x30 |
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#endif |
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.else |
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@@ -998,7 +1001,7 @@ alternative_if_not ARM64_UNMAP_KERNEL_AT |
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alternative_else_nop_endif |
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|
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#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 |
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- tramp_alias dst=x5, sym=__sdei_asm_exit_trampoline |
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+ tramp_alias dst=x5, sym=__sdei_asm_exit_trampoline, tmp=x3 |
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br x5 |
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#endif |
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SYM_CODE_END(__sdei_asm_handler) |
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