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author | Kenneth Bell <[email protected]> | 2023-01-13 17:03:41 +0000 |
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committer | Ron Evans <[email protected]> | 2023-03-12 23:53:59 +0100 |
commit | faa449a9e17aff8499d35aff300335edea4b5d21 (patch) | |
tree | b22be0d77ab3428cb09dac296e9e93d4e2056924 /src/examples | |
parent | 08cf2b25c5d1b4bbe33bcda158e368d9749ba4bc (diff) | |
download | tinygo-faa449a9e17aff8499d35aff300335edea4b5d21.tar.gz tinygo-faa449a9e17aff8499d35aff300335edea4b5d21.zip |
arm: enable functions in RAM for go & cgo
Diffstat (limited to 'src/examples')
-rw-r--r-- | src/examples/ram-func/main.go | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/src/examples/ram-func/main.go b/src/examples/ram-func/main.go new file mode 100644 index 000000000..b4556c194 --- /dev/null +++ b/src/examples/ram-func/main.go @@ -0,0 +1,93 @@ +package main + +// This example demonstrates how to use go:section to place code into RAM for +// execution. The code is present in flash in the `.data` region and copied +// into the correct place in RAM early in startup sequence (at the same time +// as non-zero global variables are initialized). +// +// This example should work on any ARM Cortex MCU. +// +// For Go code use the pragma "//go:section", for cgo use the "section" and +// "noinline" attributes. The `.ramfuncs` section is explicitly placed into +// the `.data` region by the linker script. +// +// Running the example should print out the program counter from the functions +// below. The program counters should be in different memory regions. +// +// On RP2040, for example, the output is something like this: +// +// Go in RAM: 0x20000DB4 +// Go in flash: 0x10007610 +// cgo in RAM: 0x20000DB8 +// cgo in flash: 0x10002C26 +// +// This can be confirmed using `objdump -t xxx.elf | grep main | sort`: +// +// 00000000 l df *ABS* 00000000 main +// 1000760d l F .text 00000004 main.in_flash +// 10007611 l F .text 0000000c __Thumbv6MABSLongThunk_main.in_ram +// 1000761d l F .text 0000000c __Thumbv6MABSLongThunk__Cgo_static_eea7585d7291176ad3bb_main_c_in_ram +// 1000bdb5 l O .text 00000013 main$string +// 1000bdc8 l O .text 00000013 main$string.1 +// 1000bddb l O .text 00000013 main$string.2 +// 1000bdee l O .text 00000013 main$string.3 +// 20000db1 l F .data 00000004 main.in_ram +// 20000db5 l F .data 00000004 _Cgo_static_eea7585d7291176ad3bb_main_c_in_ram +// + +import ( + "device" + "fmt" + "time" + _ "unsafe" // unsafe is required for "//go:section" +) + +/* + #define ram_func __attribute__((section(".ramfuncs"),noinline)) + + static ram_func void* main_c_in_ram() { + void* p = 0; + + asm( + "MOV %0, PC" + : "=r"(p) + ); + + return p; + } + + static void* main_c_in_flash() { + void* p = 0; + + asm( + "MOV %0, PC" + : "=r"(p) + ); + + return p; + } +*/ +import "C" + +func main() { + time.Sleep(2 * time.Second) + + fmt.Printf("Go in RAM: 0x%X\n", in_ram()) + fmt.Printf("Go in flash: 0x%X\n", in_flash()) + fmt.Printf("cgo in RAM: 0x%X\n", C.main_c_in_ram()) + fmt.Printf("cgo in flash: 0x%X\n", C.main_c_in_flash()) +} + +//go:section .ramfuncs +func in_ram() uintptr { + return device.AsmFull("MOV {}, PC", nil) +} + +// go:noinline used here to prevent function being 'inlined' into main() +// so it appears in objdump output. In normal use, go:inline is not +// required for functions running from flash (flash is the default). +// +//go:noinline +func in_flash() uintptr { + return device.AsmFull("MOV {}, PC", nil) +} |