diff options
Diffstat (limited to 'arch/tile/lib/memcpy_user_64.c')
| -rw-r--r-- | arch/tile/lib/memcpy_user_64.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/tile/lib/memcpy_user_64.c b/arch/tile/lib/memcpy_user_64.c index 4763b3aff1c..88c7016492c 100644 --- a/arch/tile/lib/memcpy_user_64.c +++ b/arch/tile/lib/memcpy_user_64.c @@ -14,7 +14,13 @@ * Do memcpy(), but trap and return "n" when a load or store faults. * * Note: this idiom only works when memcpy() compiles to a leaf function. - * If "sp" is updated during memcpy, the "jrp lr" will be incorrect. + * Here leaf function not only means it does not have calls, but also + * requires no stack operations (sp, stack frame pointer) and no + * use of callee-saved registers, else "jrp lr" will be incorrect since + * unwinding stack frame is bypassed. Since memcpy() is not complex so + * these conditions are satisfied here, but we need to be careful when + * modifying this file. This is not a clean solution but is the best + * one so far. * * Also note that we are capturing "n" from the containing scope here. */ @@ -25,6 +31,7 @@ ".pushsection .coldtext.memcpy,\"ax\";" \ "2: { move r0, %2; jrp lr };" \ ".section __ex_table,\"a\";" \ + ".align 8;" \ ".quad 1b, 2b;" \ ".popsection" \ : "=m" (*(p)) : "r" (v), "r" (n)); \ @@ -37,6 +44,7 @@ ".pushsection .coldtext.memcpy,\"ax\";" \ "2: { move r0, %2; jrp lr };" \ ".section __ex_table,\"a\";" \ + ".align 8;" \ ".quad 1b, 2b;" \ ".popsection" \ : "=r" (__v) : "m" (*(p)), "r" (n)); \ |