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| author | Chris Metcalf <cmetcalf@ezchip.com> | 2015-07-21 12:04:52 -0400 |
|---|---|---|
| committer | Chris Metcalf <cmetcalf@ezchip.com> | 2015-07-21 12:11:55 -0400 |
| commit | 0ac4f1dab3e5778c79994a89111b4eb1d247ab12 (patch) | |
| tree | bcc24bc8dd8a2c2b879e38a1c97234d9fcf420ba | |
| parent | f30d94a74a30b832354d4b87c23a4909ed24b929 (diff) | |
| download | glibc-0ac4f1dab3e5778c79994a89111b4eb1d247ab12.tar.gz glibc-0ac4f1dab3e5778c79994a89111b4eb1d247ab12.tar.xz glibc-0ac4f1dab3e5778c79994a89111b4eb1d247ab12.zip | |
tile: Fix BZ #18508 (makecontext yield infinite backtrace)
It turns out tile suffered from the same problem as S390. However, disabling CFI information for the __startcontext on tile was not sufficient to fix the problem; I think the backtracer will just blindly try to follow the link register (lr) in that case. Instead, the change adds a cfi_undefined directive for "lr" and then arranges to call __startcontext directly when the new context starts, rather than just synthesizing a return to it. In addition to being a bit easier now to understand the control flow, this also allows the cfi_undefined directive to be placed in a way that causes it to be in force at the address that the "lr" from the called function points to.
| -rw-r--r-- | ChangeLog | 7 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/tile/makecontext.c | 8 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/tile/setcontext.S | 2 |
3 files changed, 13 insertions, 4 deletions
diff --git a/ChangeLog b/ChangeLog index 490c0acf96..d855f769e1 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ +2015-07-21 Chris Metcalf <cmetcalf@ezchip.com> + + * sysdeps/unix/sysv/linux/tile/makecontext.c (__makecontext): Call + __startcontext to initialize the new context. + * sysdeps/unix/sysv/linux/tile/setcontext.S (__startcontext): Set + up CFI directive to forbid further backtracing. + 2015-07-21 Marko Myllynen <myllynen@redhat.com> * charmaps/ANSI_X3.110-1983: Remove obsolete repertoire map diff --git a/sysdeps/unix/sysv/linux/tile/makecontext.c b/sysdeps/unix/sysv/linux/tile/makecontext.c index b14b8d5cc9..c77d005672 100644 --- a/sysdeps/unix/sysv/linux/tile/makecontext.c +++ b/sysdeps/unix/sysv/linux/tile/makecontext.c @@ -52,14 +52,14 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) } va_end (ap); - /* Pass (*func) to __startcontext in pc. */ - ucp->uc_mcontext.pc = (long) func; + /* Start in the trampoline. */ + ucp->uc_mcontext.pc = (long) __startcontext; /* Set stack pointer. */ ucp->uc_mcontext.sp = (long) sp; - /* Set the return address to trampoline. */ - ucp->uc_mcontext.lr = (long) __startcontext; + /* Pass FUNC to __startcontext in r31. */ + ucp->uc_mcontext.gregs[31] = (long) func; /* Pass ucp->uc_link to __startcontext in r30. */ ucp->uc_mcontext.gregs[30] = (long) ucp->uc_link; diff --git a/sysdeps/unix/sysv/linux/tile/setcontext.S b/sysdeps/unix/sysv/linux/tile/setcontext.S index ee9edbefe1..02d6a1578c 100644 --- a/sysdeps/unix/sysv/linux/tile/setcontext.S +++ b/sysdeps/unix/sysv/linux/tile/setcontext.S @@ -190,7 +190,9 @@ END (__setcontext) weak_alias (__setcontext, setcontext) ENTRY (__startcontext) + cfi_undefined (lr) FEEDBACK_ENTER(__startcontext) + jalr r31 BEQZ r30, 1f { move r0, r30 |