https://github.com/torvalds/linux
Revision 54a015104136974262afa4b8ddd943ea70dec8a2 authored by Roland McGrath on 10 April 2008, 22:37:38 UTC, committed by Linus Torvalds on 11 April 2008, 00:28:26 UTC
The prevent_tail_call() macro works around the problem of the compiler clobbering argument words on the stack, which for asmlinkage functions is the caller's (user's) struct pt_regs. The tail/sibling-call optimization is not the only way that the compiler can decide to use stack argument words as scratch space, which we have to prevent. Other optimizations can do it too. Until we have new compiler support to make "asmlinkage" binding on the compiler's own use of the stack argument frame, we have work around all the manifestations of this issue that crop up. More cases seem to be prevented by also keeping the incoming argument variables live at the end of the function. This makes their original stack slots attractive places to leave those variables, so the compiler tends not clobber them for something else. It's still no guarantee, but it handles some observed cases that prevent_tail_call() did not. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 783e391
Tip revision: 54a015104136974262afa4b8ddd943ea70dec8a2 authored by Roland McGrath on 10 April 2008, 22:37:38 UTC
asmlinkage_protect replaces prevent_tail_call
asmlinkage_protect replaces prevent_tail_call
Tip revision: 54a0151
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| Makefile | -rw-r--r-- | 52.8 KB |
| README | -rw-r--r-- | 16.5 KB |
| REPORTING-BUGS | -rw-r--r-- | 3.1 KB |
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