From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: barebox@lists.infradead.org
Cc: Peter Mamonov <pmamonov@gmail.com>,
Peter Korsgaard <peter@korsgaard.com>,
Sascha Hauer <sha@pengutronix.de>
Subject: [PATCH v3 01/16] common: introduce HAS_ARCH_SJLJ
Date: Wed, 10 Mar 2021 09:47:45 +0100 [thread overview]
Message-ID: <20210310084800.3584-2-a.fatoum@pengutronix.de> (raw)
In-Reply-To: <20210310084800.3584-1-a.fatoum@pengutronix.de>
From: Ahmad Fatoum <ahmad@a3f.at>
setjmp stores the registers comprising the execution context into a
jmp_buf and longjmp switches to that context and continues execution just
after the setjmp that allocated that jmp_buf.
setjmp/longjmp can have multiple uses:
- Handle return from firmware that clobbers registers. This is why we
already have a setjmp/longjmp ARM
- Do exception handling[1]
- Port over scripting language VMs that use sjlj for context switching
- Implement stackless coroutines in C.
These coroutines would be stackless, because jumping to a setjmp down the
call stack means that the code there will clobber the stack below it.
On resuming the coroutine, it will run with a stack changed in the
interim leading to undefined behavior.
There are ways around that without resorting to custom Assembly:
- Allocate a buffer on the scheduler's stack, so coroutine can
grow into them
-> Problem: exploits Undefined behavior
- Yield first time on scheduler stack, then patch jmp_buf to point at
another stack
-> Problem: Code switching stacks should not itself use the stack
- Construct a new jmp_buf with user-supplied return address and stack top:
int initjmp(jmp_buf jmp, void __noreturn (*func)(void), void *stack_top);
The latter could also be reused as a portable way of setting up a stack
in early init code.
We are going to implement green threads in later commits, so add a
symbol that can be selected to indicate architecture support for setjmp,
longjmp and the new initjmp.
[1]: https://www.spinics.net/lists/u-boot-v2/msg41322.html
Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
---
common/Kconfig | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/common/Kconfig b/common/Kconfig
index edadcc9f4979..c0ff57bcdba4 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -28,6 +28,11 @@ config HAS_DMA
Drivers that depend on a DMA implementation can depend on this
config, so that you don't get a compilation error.
+config HAS_ARCH_SJLJ
+ bool
+ help
+ Architecture has support implemented for setjmp()/longjmp()/initjmp()
+
config GENERIC_GPIO
bool
--
2.29.2
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next prev parent reply other threads:[~2021-03-10 8:49 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 8:47 [PATCH v3 00/16] common: introduce bthreads, co-operative Ahmad Fatoum
2021-03-10 8:47 ` Ahmad Fatoum [this message]
2021-03-10 8:47 ` [PATCH v3 02/16] ARM: asm: setjmp: annotate setjmp/longjmp for GCC Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 03/16] ARM: asm: setjmp: implement coroutine dependency initjmp() Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 04/16] sandbox: asm: implement setjmp/longjmp/initjmp Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 05/16] riscv: Add asm/asm.h Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 06/16] riscv: Add asm/linkage.h Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 07/16] riscv: Implement setjmp/longjmp/initjmp for RV32I Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 08/16] mips: Add linkage.h Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 09/16] mips: Implement setjmp/longjmp/initjmp for 32BIT Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 10/16] powerpc: Implement initjmp/setjmp/longjmp Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 11/16] x86: implement setjmp/longjmp/initjmp Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 12/16] common: poller: replace explicit calls to poller_call() with resched() Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 13/16] console: unconditionally run resched() in ctrlc() Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 14/16] common: introduce bthreads, co-operative barebox threads Ahmad Fatoum
2021-03-10 8:47 ` [PATCH v3 15/16] commands: add new bthread test command Ahmad Fatoum
2021-03-10 8:48 ` [PATCH v3 16/16] RFC: led: migrate from poller to bthread Ahmad Fatoum
2021-03-15 8:34 ` [PATCH v3 00/16] common: introduce bthreads, co-operative Sascha Hauer
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