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ARM: 9390/2: lib: Annotate loop delay instructions for CFI

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When we annotate the loop delay code with SYM_TYPED_FUNC_START()
a function prototype signature will be emitted into the object
file above each site called from C, and the delay loop code is
using "fallthroughs" from the different assembly callbacks. This
will not work as the execution flow will run into the prototype
signatures.

Rewrite the code to use explicit branches to the other code
segments and annotate the code using SYM_TYPED_FUNC_START().

Tested on the ARM Versatile which uses the calibrated loop delay.

Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Linus Walleij 2024-04-23 08:50:38 +01:00 committed by Russell King (Oracle)
parent 393999fa96
commit 7339fb11ae
1 changed files with 10 additions and 6 deletions
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16
arch/arm/lib/delay-loop.S
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@ -5,6 +5,7 @@
* Copyright (C) 1995, 1996 Russell King
*/
#include <linux/linkage.h>
#include <linux/cfi_types.h>
#include <asm/assembler.h>
#include <asm/delay.h>
@ -24,21 +25,26 @@
* HZ <= 1000
*/
ENTRY(__loop_udelay)
SYM_TYPED_FUNC_START(__loop_udelay)
ldr r2, .LC1
mul r0, r2, r0 @ r0 = delay_us * UDELAY_MULT
ENTRY(__loop_const_udelay) @ 0 <= r0 <= 0xfffffaf0
b __loop_const_udelay
SYM_FUNC_END(__loop_udelay)
SYM_TYPED_FUNC_START(__loop_const_udelay) @ 0 <= r0 <= 0xfffffaf0
ldr r2, .LC0
ldr r2, [r2]
umull r1, r0, r2, r0 @ r0-r1 = r0 * loops_per_jiffy
adds r1, r1, #0xffffffff @ rounding up ...
adcs r0, r0, r0 @ and right shift by 31
reteq lr
b __loop_delay
SYM_FUNC_END(__loop_const_udelay)
.align 3
@ Delay routine
ENTRY(__loop_delay)
SYM_TYPED_FUNC_START(__loop_delay)
subs r0, r0, #1
#if 0
retls lr
@ -58,6 +64,4 @@ ENTRY(__loop_delay)
#endif
bhi __loop_delay
ret lr
ENDPROC(__loop_udelay)
ENDPROC(__loop_const_udelay)
ENDPROC(__loop_delay)
SYM_FUNC_END(__loop_delay)