diff options
author | Marcel Ziswiler <marcel.ziswiler@toradex.com> | 2020-05-19 23:01:26 +0200 |
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committer | Marcel Ziswiler <marcel.ziswiler@toradex.com> | 2020-05-19 23:37:01 +0200 |
commit | 2ae782ca839e0ee07de37122ddea362adff2e975 (patch) | |
tree | df6b1a190760f51465122ca4c13492d5ac5984c6 /arch/mips/include/asm/compiler.h | |
parent | 0a8ab17689e628c84a666195bfc6ab85d11cf057 (diff) | |
parent | 0661b3d6cfd774e28a2e2ba90a3d87479e5c399b (diff) |
Merge tag 'v4.9.220' into 4.9-2.3.x-imx
This is the 4.9.220 stable release
Conflicts:
arch/arm/Kconfig.debug
arch/arm/boot/dts/imx7s.dtsi
arch/arm/mach-imx/common.h
arch/arm/mach-imx/cpuidle-imx6q.c
arch/arm/mach-imx/cpuidle-imx6sx.c
arch/arm/mach-imx/suspend-imx6.S
block/blk-core.c
drivers/crypto/caam/caamalg.c
drivers/crypto/mxs-dcp.c
drivers/dma/imx-sdma.c
drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
drivers/input/keyboard/imx_keypad.c
drivers/input/keyboard/snvs_pwrkey.c
drivers/mmc/host/sdhci.c
drivers/net/can/flexcan.c
drivers/net/ethernet/freescale/fec_main.c
drivers/net/phy/phy_device.c
drivers/net/wireless/ath/ath10k/pci.c
drivers/tty/serial/imx.c
drivers/usb/dwc3/gadget.c
drivers/usb/host/xhci.c
include/linux/blkdev.h
include/linux/cpu.h
include/linux/platform_data/dma-imx-sdma.h
kernel/cpu.c
net/wireless/util.c
sound/soc/fsl/Kconfig
sound/soc/fsl/fsl_esai.c
sound/soc/fsl/fsl_sai.c
sound/soc/fsl/imx-sgtl5000.c
Diffstat (limited to 'arch/mips/include/asm/compiler.h')
-rw-r--r-- | arch/mips/include/asm/compiler.h | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/arch/mips/include/asm/compiler.h b/arch/mips/include/asm/compiler.h index e081a265f422..cc2eb1b06050 100644 --- a/arch/mips/include/asm/compiler.h +++ b/arch/mips/include/asm/compiler.h @@ -8,6 +8,41 @@ #ifndef _ASM_COMPILER_H #define _ASM_COMPILER_H +/* + * With GCC 4.5 onwards we can use __builtin_unreachable to indicate to the + * compiler that a particular code path will never be hit. This allows it to be + * optimised out of the generated binary. + * + * Unfortunately at least GCC 4.6.3 through 7.3.0 inclusive suffer from a bug + * that can lead to instructions from beyond an unreachable statement being + * incorrectly reordered into earlier delay slots if the unreachable statement + * is the only content of a case in a switch statement. This can lead to + * seemingly random behaviour, such as invalid memory accesses from incorrectly + * reordered loads or stores. See this potential GCC fix for details: + * + * https://gcc.gnu.org/ml/gcc-patches/2015-09/msg00360.html + * + * It is unclear whether GCC 8 onwards suffer from the same issue - nothing + * relevant is mentioned in GCC 8 release notes and nothing obviously relevant + * stands out in GCC commit logs, but these newer GCC versions generate very + * different code for the testcase which doesn't exhibit the bug. + * + * GCC also handles stack allocation suboptimally when calling noreturn + * functions or calling __builtin_unreachable(): + * + * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365 + * + * We work around both of these issues by placing a volatile asm statement, + * which GCC is prevented from reordering past, prior to __builtin_unreachable + * calls. + * + * The .insn statement is required to ensure that any branches to the + * statement, which sadly must be kept due to the asm statement, are known to + * be branches to code and satisfy linker requirements for microMIPS kernels. + */ +#undef barrier_before_unreachable +#define barrier_before_unreachable() asm volatile(".insn") + #if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) #define GCC_IMM_ASM() "n" #define GCC_REG_ACCUM "$0" |