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ARM: memcpy: use frame pointer as unwind anchor
The memcpy template is a bit unusual in the way it manages the stack
pointer: depending on the execution path through the function, the SP
assumes different values as different subsets of the register file are
preserved and restored again. This is problematic when it comes to EHABI
unwind info, as it is not instruction accurate, and does not allow
tracking the SP value as it changes.
Commit 279f487e0b ("ARM: 8225/1: Add unwinding support for memory
copy functions") addressed this by carving up the function in different
chunks as far as the unwinder is concerned, and keeping a set of unwind
directives for each of them, each corresponding with the state of the
stack pointer during execution of the chunk in question. This not only
duplicates unwind info unnecessarily, but it also complicates unwinding
the stack upon overflow.
Instead, let's do what the compiler does when the SP is updated halfway
through a function, which is to use a frame pointer and emit the
appropriate unwind directives to communicate this to the unwinder.
Note that Thumb-2 uses R7 for this, while ARM uses R11 aka FP. So let's
avoid touching R7 in the body of the template, so that Thumb-2 can use
it as the frame pointer. R11 was not modified in the first place.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M
This commit is contained in:
Ard Biesheuvel
parent
9974f85776
commit
ba999a0402
@ -91,18 +91,15 @@
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strb\cond \reg, [\ptr], #1
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.endm
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.macro enter reg1 reg2
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.macro enter regs:vararg
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mov r3, #0
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stmdb sp!, {r0, r2, r3, \reg1, \reg2}
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UNWIND( .save {r0, r2, r3, \regs} )
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stmdb sp!, {r0, r2, r3, \regs}
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.endm
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.macro usave reg1 reg2
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UNWIND( .save {r0, r2, r3, \reg1, \reg2} )
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.endm
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.macro exit reg1 reg2
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.macro exit regs:vararg
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add sp, sp, #8
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ldmfd sp!, {r0, \reg1, \reg2}
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ldmfd sp!, {r0, \regs}
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.endm
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.text
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@ -69,13 +69,10 @@
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* than one 32bit instruction in Thumb-2)
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*/
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UNWIND( .fnstart )
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enter r4, lr
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UNWIND( .fnend )
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UNWIND( .fnstart )
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usave r4, lr @ in first stmdb block
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enter r4, UNWIND(fpreg,) lr
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UNWIND( .setfp fpreg, sp )
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UNWIND( mov fpreg, sp )
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subs r2, r2, #4
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blt 8f
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@ -86,12 +83,7 @@
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bne 10f
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1: subs r2, r2, #(28)
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stmfd sp!, {r5 - r8}
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UNWIND( .fnend )
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UNWIND( .fnstart )
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usave r4, lr
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UNWIND( .save {r5 - r8} ) @ in second stmfd block
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stmfd sp!, {r5, r6, r8, r9}
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blt 5f
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CALGN( ands ip, r0, #31 )
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@ -110,9 +102,9 @@
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PLD( pld [r1, #92] )
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3: PLD( pld [r1, #124] )
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4: ldr8w r1, r3, r4, r5, r6, r7, r8, ip, lr, abort=20f
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4: ldr8w r1, r3, r4, r5, r6, r8, r9, ip, lr, abort=20f
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subs r2, r2, #32
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str8w r0, r3, r4, r5, r6, r7, r8, ip, lr, abort=20f
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str8w r0, r3, r4, r5, r6, r8, r9, ip, lr, abort=20f
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bge 3b
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PLD( cmn r2, #96 )
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PLD( bge 4b )
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@ -132,8 +124,8 @@
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ldr1w r1, r4, abort=20f
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ldr1w r1, r5, abort=20f
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ldr1w r1, r6, abort=20f
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ldr1w r1, r7, abort=20f
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ldr1w r1, r8, abort=20f
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ldr1w r1, r9, abort=20f
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ldr1w r1, lr, abort=20f
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#if LDR1W_SHIFT < STR1W_SHIFT
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@ -150,17 +142,14 @@
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str1w r0, r4, abort=20f
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str1w r0, r5, abort=20f
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str1w r0, r6, abort=20f
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str1w r0, r7, abort=20f
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str1w r0, r8, abort=20f
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str1w r0, r9, abort=20f
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str1w r0, lr, abort=20f
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CALGN( bcs 2b )
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7: ldmfd sp!, {r5 - r8}
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UNWIND( .fnend ) @ end of second stmfd block
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7: ldmfd sp!, {r5, r6, r8, r9}
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UNWIND( .fnstart )
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usave r4, lr @ still in first stmdb block
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8: movs r2, r2, lsl #31
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ldr1b r1, r3, ne, abort=21f
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ldr1b r1, r4, cs, abort=21f
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@ -169,7 +158,7 @@
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str1b r0, r4, cs, abort=21f
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str1b r0, ip, cs, abort=21f
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exit r4, pc
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exit r4, UNWIND(fpreg,) pc
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9: rsb ip, ip, #4
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cmp ip, #2
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@ -189,13 +178,10 @@
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ldr1w r1, lr, abort=21f
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beq 17f
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bgt 18f
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UNWIND( .fnend )
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.macro forward_copy_shift pull push
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UNWIND( .fnstart )
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usave r4, lr @ still in first stmdb block
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subs r2, r2, #28
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blt 14f
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@ -205,12 +191,8 @@
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CALGN( subcc r2, r2, ip )
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CALGN( bcc 15f )
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11: stmfd sp!, {r5 - r9}
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UNWIND( .fnend )
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11: stmfd sp!, {r5, r6, r8 - r10}
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UNWIND( .fnstart )
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usave r4, lr
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UNWIND( .save {r5 - r9} ) @ in new second stmfd block
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PLD( pld [r1, #0] )
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PLD( subs r2, r2, #96 )
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PLD( pld [r1, #28] )
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@ -219,35 +201,32 @@
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PLD( pld [r1, #92] )
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12: PLD( pld [r1, #124] )
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13: ldr4w r1, r4, r5, r6, r7, abort=19f
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13: ldr4w r1, r4, r5, r6, r8, abort=19f
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mov r3, lr, lspull #\pull
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subs r2, r2, #32
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ldr4w r1, r8, r9, ip, lr, abort=19f
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ldr4w r1, r9, r10, ip, lr, abort=19f
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orr r3, r3, r4, lspush #\push
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mov r4, r4, lspull #\pull
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orr r4, r4, r5, lspush #\push
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mov r5, r5, lspull #\pull
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orr r5, r5, r6, lspush #\push
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mov r6, r6, lspull #\pull
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orr r6, r6, r7, lspush #\push
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mov r7, r7, lspull #\pull
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orr r7, r7, r8, lspush #\push
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orr r6, r6, r8, lspush #\push
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mov r8, r8, lspull #\pull
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orr r8, r8, r9, lspush #\push
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mov r9, r9, lspull #\pull
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orr r9, r9, ip, lspush #\push
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orr r9, r9, r10, lspush #\push
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mov r10, r10, lspull #\pull
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orr r10, r10, ip, lspush #\push
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mov ip, ip, lspull #\pull
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orr ip, ip, lr, lspush #\push
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str8w r0, r3, r4, r5, r6, r7, r8, r9, ip, abort=19f
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str8w r0, r3, r4, r5, r6, r8, r9, r10, ip, abort=19f
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bge 12b
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PLD( cmn r2, #96 )
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PLD( bge 13b )
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ldmfd sp!, {r5 - r9}
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UNWIND( .fnend ) @ end of the second stmfd block
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ldmfd sp!, {r5, r6, r8 - r10}
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UNWIND( .fnstart )
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usave r4, lr @ still in first stmdb block
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14: ands ip, r2, #28
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beq 16f
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@ -262,7 +241,6 @@
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16: sub r1, r1, #(\push / 8)
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b 8b
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UNWIND( .fnend )
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.endm
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@ -273,6 +251,7 @@
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18: forward_copy_shift pull=24 push=8
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UNWIND( .fnend )
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/*
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* Abort preamble and completion macros.
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@ -282,13 +261,13 @@
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*/
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.macro copy_abort_preamble
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19: ldmfd sp!, {r5 - r9}
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19: ldmfd sp!, {r5, r6, r8 - r10}
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b 21f
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20: ldmfd sp!, {r5 - r8}
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20: ldmfd sp!, {r5, r6, r8, r9}
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21:
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.endm
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.macro copy_abort_end
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ldmfd sp!, {r4, pc}
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ldmfd sp!, {r4, UNWIND(fpreg,) pc}
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.endm
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@ -90,18 +90,15 @@
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strusr \reg, \ptr, 1, \cond, abort=\abort
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.endm
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.macro enter reg1 reg2
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.macro enter regs:vararg
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mov r3, #0
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stmdb sp!, {r0, r2, r3, \reg1, \reg2}
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UNWIND( .save {r0, r2, r3, \regs} )
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stmdb sp!, {r0, r2, r3, \regs}
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.endm
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.macro usave reg1 reg2
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UNWIND( .save {r0, r2, r3, \reg1, \reg2} )
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.endm
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.macro exit reg1 reg2
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.macro exit regs:vararg
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add sp, sp, #8
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ldmfd sp!, {r0, \reg1, \reg2}
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ldmfd sp!, {r0, \regs}
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.endm
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.text
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@ -42,16 +42,13 @@
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strb\cond \reg, [\ptr], #1
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.endm
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.macro enter reg1 reg2
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stmdb sp!, {r0, \reg1, \reg2}
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.macro enter regs:vararg
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UNWIND( .save {r0, \regs} )
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stmdb sp!, {r0, \regs}
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.endm
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.macro usave reg1 reg2
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UNWIND( .save {r0, \reg1, \reg2} )
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.endm
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.macro exit reg1 reg2
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ldmfd sp!, {r0, \reg1, \reg2}
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.macro exit regs:vararg
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ldmfd sp!, {r0, \regs}
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.endm
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.text
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