From c8336fc4ba3fa086b2bb636dbeb764fc0f4f51e8 Mon Sep 17 00:00:00 2001 From: Keith Packard Date: Sat, 4 Mar 2023 00:08:24 -0800 Subject: [PATCH] Fix TLS and stack alignment when using picolibc Both the TLS block and stack must be correctly aligned when using picolibc. The architecture stack alignment is represented by the portBYTE_ALIGNMENT_MASK and the TLS block alignment is provided by the Picolibc _tls_align() inline function for Picolibc version 1.8 and above. For older versions of Picolibc, we'll assume that the TLS block requires the same alignment as the stack. For downward growing stacks, this requires aligning the start of the TLS block to the maximum of the stack alignment and the TLS alignment. With this, both the TLS block and stack will now be correctly aligned. For upward growing stacks, the two areas must be aligned independently; the TLS block is aligned from the start of the stack, then the tls space is allocated, and then the stack is aligned above that. It's probably useful to know here that the linker ensures that variables within the TLS block are assigned offsets that match their alignment requirements. If the TLS block itself is correctly aligned, then everything within will also be. I have only tested the downward growing stack branch of this patch. Signed-off-by: Keith Packard --- include/picolibc-freertos.h | 41 ++++++++++++++++++++++++++++--------- 1 file changed, 31 insertions(+), 10 deletions(-) diff --git a/include/picolibc-freertos.h b/include/picolibc-freertos.h index 472d71e9932..467f7a97091 100644 --- a/include/picolibc-freertos.h +++ b/include/picolibc-freertos.h @@ -43,22 +43,43 @@ #define configTLS_BLOCK_TYPE void * +#define picolibcTLS_SIZE ( ( portPOINTER_SIZE_TYPE ) _tls_size() ) +#define picolibcSTACK_ALIGNMENT_MASK ( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) + +#if __PICOLIBC_MAJOR__ > 1 || __PICOLIBC_MINOR__ >= 8 + +/* Picolibc 1.8 and newer have explicit alignment values provided + * by the _tls_align() inline */ + #define picolibcTLS_ALIGNMENT_MASK ( ( portPOINTER_SIZE_TYPE ) ( _tls_align() - 1 ) ) +#else + +/* For older Picolibc versions, use the general port alignment value */ + #define picolibcTLS_ALIGNMENT_MASK ( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) +#endif + /* Allocate thread local storage block off the end of the * stack. The _tls_size() function returns the size (in * bytes) of the total TLS area used by the application */ #if ( portSTACK_GROWTH < 0 ) - #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack ) \ - do { \ - pxTopOfStack = ( StackType_t * ) ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack ) - _tls_size() ); \ - xTLSBlock = pxTopOfStack; \ - _init_tls( xTLSBlock ); \ + + #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack ) \ + do { \ + pxTopOfStack = ( StackType_t * ) ( ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack ) \ + - picolibcTLS_SIZE ) & ~ \ + configMAX( picolibcSTACK_ALIGNMENT_MASK, \ + picolibcTLS_ALIGNMENT_MASK ) ); \ + xTLSBlock = pxTopOfStack; \ + _init_tls( xTLSBlock ); \ } while( 0 ) #else /* portSTACK_GROWTH */ - #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack ) \ - do { \ - xTLSBlock = pxTopOfStack; \ - pxTopOfStack = ( StackType_t * ) ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack ) + _tls_size() ); \ - _init_tls( xTLSBlock ); \ + #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack ) \ + do { \ + xTLSBlock = ( void * ) ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack + \ + picolibcTLS_ALIGNMENT_MASK ) & ~picolibcTLS_ALIGNMENT_MASK ); \ + pxTopOfStack = ( StackType_t * ) ( ( ( ( ( portPOINTER_SIZE_TYPE ) xTLSBlock ) + \ + picolibcTLS_SIZE ) + picolibcSTACK_ALIGNMENT_MASK ) & \ + ~picolibcSTACK_ALIGNMENT_MASK ); \ + _init_tls( xTLSBlock ); \ } while( 0 ) #endif /* portSTACK_GROWTH */