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UPSTREAM: arm64: entry: Allow tramp_alias to access symbols after the 4K boundary

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commit 6c5bf79b69f911560fbf82214c0971af6e58e682 upstream.

Systems using kpti enter and exit the kernel through a trampoline mapping
that is always mapped, even when the kernel is not. tramp_valias is a macro
to find the address of a symbol in the trampoline mapping.

Adding extra sets of vectors will expand the size of the entry.tramp.text
section to beyond 4K. tramp_valias will be unable to generate addresses
for symbols beyond 4K as it uses the 12 bit immediate of the add
instruction.

As there are now two registers available when tramp_alias is called,
use the extra register to avoid the 4K limit of the 12 bit immediate.

Bug: 215557547
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ic7a70f79baeacb3c8d12c396009968e563a2e69a
This commit is contained in:
James Morse
2021-11-24 11:40:18 +00:00
committed by Greg Kroah-Hartman
parent 6e48449c91
commit 0defb52ce6
1 changed files with 8 additions and 5 deletions
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13
arch/arm64/kernel/entry.S
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@@ -128,9 +128,12 @@
.org .Lventry_start\@ + 128 // Did we overflow the ventry slot? .org .Lventry_start\@ + 128 // Did we overflow the ventry slot?
.endm .endm
.macro tramp_alias, dst, sym .macro tramp_alias, dst, sym, tmp
mov_q \dst, TRAMP_VALIAS mov_q \dst, TRAMP_VALIAS
add \dst, \dst, #(\sym - .entry.tramp.text) adr_l \tmp, \sym
add \dst, \dst, \tmp
adr_l \tmp, .entry.tramp.text
sub \dst, \dst, \tmp
.endm .endm
/* /*
@@ -466,10 +469,10 @@ alternative_else_nop_endif
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
bne 4f bne 4f
msr far_el1, x29 msr far_el1, x29
tramp_alias x30, tramp_exit_native tramp_alias x30, tramp_exit_native, x29
br x30 br x30
4: 4:
tramp_alias x30, tramp_exit_compat tramp_alias x30, tramp_exit_compat, x29
br x30 br x30
#endif #endif
.else .else
@@ -1228,7 +1231,7 @@ alternative_if_not ARM64_UNMAP_KERNEL_AT_EL0
alternative_else_nop_endif alternative_else_nop_endif
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
tramp_alias dst=x5, sym=__sdei_asm_exit_trampoline tramp_alias dst=x5, sym=__sdei_asm_exit_trampoline, tmp=x3
br x5 br x5
#endif #endif
SYM_CODE_END(__sdei_asm_handler) SYM_CODE_END(__sdei_asm_handler)