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| author | Arun Chandran <achandran@mvista.com> | 2014-08-18 11:06:58 +0200 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2014-09-08 15:39:18 +0200 |
| commit | 5e051531447259e5df95c44bccb69979537c19e4 (patch) | |
| tree | 16ab7c440cbace7ed2d321949f2b48dadc86a987 /arch/arm64/mm | |
| parent | arm64/efi: efistub: don't abort if base of DRAM is occupied (diff) | |
| download | linux-5e051531447259e5df95c44bccb69979537c19e4.tar.xz linux-5e051531447259e5df95c44bccb69979537c19e4.zip | |
arm64: convert part of soft_restart() to assembly
The current soft_restart() and setup_restart implementations incorrectly
assume that compiler will not spill/fill values to/from stack. However
this assumption seems to be wrong, revealed by the disassembly of the
currently existing code (v3.16) built with Linaro GCC 4.9-2014.05.
ffffffc000085224 <soft_restart>:
ffffffc000085224: a9be7bfd stp x29, x30, [sp,#-32]!
ffffffc000085228: 910003fd mov x29, sp
ffffffc00008522c: f9000fa0 str x0, [x29,#24]
ffffffc000085230: 94003d21 bl ffffffc0000946b4 <setup_mm_for_reboot>
ffffffc000085234: 94003b33 bl ffffffc000093f00 <flush_cache_all>
ffffffc000085238: 94003dfa bl ffffffc000094a20 <cpu_cache_off>
ffffffc00008523c: 94003b31 bl ffffffc000093f00 <flush_cache_all>
ffffffc000085240: b0003321 adrp x1, ffffffc0006ea000 <reset_devices>
ffffffc000085244: f9400fa0 ldr x0, [x29,#24] ----> spilled addr
ffffffc000085248: f942fc22 ldr x2, [x1,#1528] ----> global memstart_addr
ffffffc00008524c: f0000061 adrp x1, ffffffc000094000 <__inval_cache_range+0x40>
ffffffc000085250: 91290021 add x1, x1, #0xa40
ffffffc000085254: 8b010041 add x1, x2, x1
ffffffc000085258: d2c00802 mov x2, #0x4000000000 // #274877906944
ffffffc00008525c: 8b020021 add x1, x1, x2
ffffffc000085260: d63f0020 blr x1
...
Here the compiler generates memory accesses after the cache is disabled,
loading stale values for the spilled value and global variable. As we cannot
control when the compiler will access memory we must rewrite the
functions in assembly to stash values we need in registers prior to
disabling the cache, avoiding the use of memory.
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Arun Chandran <achandran@mvista.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/mm')
| -rw-r--r-- | arch/arm64/mm/proc.S | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index 7736779c9809..4e778b13291b 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -76,6 +76,21 @@ ENTRY(cpu_reset) ret x0 ENDPROC(cpu_reset) +ENTRY(cpu_soft_restart) + /* Save address of cpu_reset() and reset address */ + mov x19, x0 + mov x20, x1 + + /* Turn D-cache off */ + bl cpu_cache_off + + /* Push out all dirty data, and ensure cache is empty */ + bl flush_cache_all + + mov x0, x20 + ret x19 +ENDPROC(cpu_soft_restart) + /* * cpu_do_idle() * |