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examples/ucontext-cp.c: cope with variable SIGSTKSZ
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BZ: 1980845
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commit 8aac320ae8445c5434ab3be1761414a5247e5d42
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Author: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Tue Apr 13 16:03:19 2021 +0100
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examples/ucontext-cp.c: cope with variable SIGSTKSZ
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The size of C arrays at file scope must be constant. The following
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compiler error occurs with recent upstream glibc (2.33.9000):
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CC ucontext-cp
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ucontext-cp.c:31:23: error: variably modified ‘stack_buf’ at file scope
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31 | unsigned char stack_buf[SIGSTKSZ];
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| ^~~~~~~~~
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make[1]: *** [Makefile:26: ucontext-cp] Error 1
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The following glibc commit changed SIGSTKSZ from a constant value to a
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variable:
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commit 6c57d320484988e87e446e2e60ce42816bf51d53
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Author: H.J. Lu <hjl.tools@gmail.com>
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Date: Mon Feb 1 11:00:38 2021 -0800
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sysconf: Add _SC_MINSIGSTKSZ/_SC_SIGSTKSZ [BZ #20305]
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...
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+# define SIGSTKSZ sysconf (_SC_SIGSTKSZ)
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Allocate the stack buffer explicitly to avoid declaring an array at file
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scope.
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Cc: H.J. Lu <hjl.tools@gmail.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Jens Axboe <axboe@kernel.dk>
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diff --git a/examples/ucontext-cp.c b/examples/ucontext-cp.c
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index 0b2a6b5..ea0c934 100644
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--- a/examples/ucontext-cp.c
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+++ b/examples/ucontext-cp.c
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@@ -28,7 +28,7 @@
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typedef struct {
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struct io_uring *ring;
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- unsigned char stack_buf[SIGSTKSZ];
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+ unsigned char *stack_buf;
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ucontext_t ctx_main, ctx_fnew;
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} async_context;
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@@ -115,8 +115,13 @@ static int setup_context(async_context *pctx, struct io_uring *ring)
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perror("getcontext");
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return -1;
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}
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- pctx->ctx_fnew.uc_stack.ss_sp = &pctx->stack_buf;
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- pctx->ctx_fnew.uc_stack.ss_size = sizeof(pctx->stack_buf);
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+ pctx->stack_buf = malloc(SIGSTKSZ);
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+ if (!pctx->stack_buf) {
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+ perror("malloc");
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+ return -1;
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+ }
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+ pctx->ctx_fnew.uc_stack.ss_sp = pctx->stack_buf;
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+ pctx->ctx_fnew.uc_stack.ss_size = SIGSTKSZ;
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pctx->ctx_fnew.uc_link = &pctx->ctx_main;
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return 0;
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@@ -174,6 +179,7 @@ static void copy_file_wrapper(arguments_bundle *pbundle)
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free(iov.iov_base);
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close(pbundle->infd);
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close(pbundle->outfd);
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+ free(pbundle->pctx->stack_buf);
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free(pbundle->pctx);
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free(pbundle);
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