101 lines
3.1 KiB
Diff
101 lines
3.1 KiB
Diff
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commit a55e109709af55e6ed67d3f9536cac5d929c982e
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Author: Carlos O'Donell <carlos@redhat.com>
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Date: Wed Sep 5 01:16:42 2018 -0400
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Fix tst-setcontext9 for optimized small stacks.
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If the compiler reduces the stack usage in function f1 before calling
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into function f2, then when we swapcontext back to f1 and continue
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execution we may overwrite registers that were spilled to the stack
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while f2 was executing. Later when we return to f2 the corrupt
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registers will be reloaded from the stack and the test will crash. This
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was most commonly observed on i686 with __x86.get_pc_thunk.dx and
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needing to save and restore $edx. Overall i686 has few registers and
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the spilling to the stack is bound to happen, therefore the solution to
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making this test robust is to split function f1 into two parts f1a and
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f1b, and allocate f1b it's own stack such that subsequent execution does
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not overwrite the stack in use by function f2.
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Tested on i686 and x86_64.
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Signed-off-by: Carlos O'Donell <carlos@redhat.com>
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(cherry picked from commit 791b350dc725545e3f9b5db0f97ebdbc60c9735f)
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diff --git a/stdlib/tst-setcontext9.c b/stdlib/tst-setcontext9.c
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index 4636ce9030fa38a7..db8355766ca7b906 100644
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--- a/stdlib/tst-setcontext9.c
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+++ b/stdlib/tst-setcontext9.c
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@@ -41,26 +41,55 @@ f2 (void)
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}
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static void
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-f1 (void)
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+f1b (void)
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{
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- puts ("start f1");
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- if (getcontext (&ctx[2]) != 0)
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- {
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- printf ("%s: getcontext: %m\n", __FUNCTION__);
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- exit (EXIT_FAILURE);
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- }
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if (done)
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{
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- puts ("set context in f1");
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+ puts ("set context in f1b");
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if (setcontext (&ctx[3]) != 0)
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{
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printf ("%s: setcontext: %m\n", __FUNCTION__);
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exit (EXIT_FAILURE);
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}
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}
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+ exit (EXIT_FAILURE);
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+}
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+
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+static void
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+f1a (void)
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+{
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+ char st2[32768];
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+ puts ("start f1a");
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+ if (getcontext (&ctx[2]) != 0)
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+ {
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+ printf ("%s: getcontext: %m\n", __FUNCTION__);
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+ exit (EXIT_FAILURE);
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+ }
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+ ctx[2].uc_stack.ss_sp = st2;
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+ ctx[2].uc_stack.ss_size = sizeof st2;
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+ ctx[2].uc_link = &ctx[0];
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+ makecontext (&ctx[2], (void (*) (void)) f1b, 0);
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f2 ();
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}
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+/* The execution path through the test looks like this:
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+ do_test (call)
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+ -> "making contexts"
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+ -> "swap contexts"
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+ f1a (via swapcontext to ctx[1], with alternate stack)
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+ -> "start f1a"
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+ f2 (call)
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+ -> "swap contexts in f2"
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+ f1b (via swapcontext to ctx[2], with alternate stack)
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+ -> "set context in f1b"
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+ do_test (via setcontext to ctx[3], main stack)
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+ -> "setcontext"
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+ f2 (via setcontext to ctx[4], with alternate stack)
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+ -> "end f2"
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+
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+ We must use an alternate stack for f1b, because if we don't then the
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+ result of executing an earlier caller may overwrite registers
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+ spilled to the stack in f2. */
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static int
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do_test (void)
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{
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@@ -79,7 +108,7 @@ do_test (void)
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ctx[1].uc_stack.ss_sp = st1;
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ctx[1].uc_stack.ss_size = sizeof st1;
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ctx[1].uc_link = &ctx[0];
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- makecontext (&ctx[1], (void (*) (void)) f1, 0);
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+ makecontext (&ctx[1], (void (*) (void)) f1a, 0);
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puts ("swap contexts");
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if (swapcontext (&ctx[3], &ctx[1]) != 0)
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{
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