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subsys/logging: Add compiler barriers to msg stack allocation #46967

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Jul 13, 2022
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subsys/logging: Add compiler barriers to msg stack allocation #46967

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12 changes: 12 additions & 0 deletions include/zephyr/logging/log_msg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,17 @@ enum z_log_msg_mode {
Z_LOG_MSG2_ALIGNMENT), \
sizeof(uint32_t))

/*
* With Zephyr SDK 0.14.2, aarch64-zephyr-elf-gcc (10.3.0) fails to ensure $sp
* is below the active memory during message construction. As a result,
* interrupts happening in the middle of that process can end up smashing active
* data and causing a logging fault. Work around this by inserting a compiler
* barrier after the allocation and before any use to make sure GCC moves the
* stack pointer soon enough
*/

#define Z_LOG_ARM64_VLA_PROTECT() compiler_barrier()
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Since its only for arm64 what about:
#define Z_LOG_ARM64_VLA_PROTECT() IF_ENABLED(CONFIG_ARM64, (copiler_barrier()))

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I thought #46986 was on arm32? Even if not, I still wonder if this is a problem in general GCC code or is specific to arm64?

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According to #46967 (comment) it's not related and still reproduces after adding the barrier. If we suspect that it's affecting more platforms than im ok with keeping it for all platforms but then maybe remove ARM64 from the name and only mention in the comment that it has been seen on arm64 and other platforms may be affected as well.


#define Z_LOG_MSG2_STACK_CREATE(_cstr_cnt, _domain_id, _source, _level, _data, _dlen, ...) \
do { \
int _plen; \
Expand All @@ -211,6 +222,7 @@ do { \
} \
struct log_msg *_msg; \
Z_LOG_MSG2_ON_STACK_ALLOC(_msg, Z_LOG_MSG2_LEN(_plen, 0)); \
Z_LOG_ARM64_VLA_PROTECT(); \
if (_plen) { \
CBPRINTF_STATIC_PACKAGE(_msg->data, _plen, \
_plen, Z_LOG_MSG2_ALIGN_OFFSET, flags, \
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