LAHF is not support in all 64-bit processors

[derekbruening]

From qin.zhao@gmail.com on July 29, 2009 14:26:14

According to Intel Manual, LAHF instruction is valid in 64-bit mode only if
CPUID.80000001H:ECX.LAHF-SAHF[bit 0] = 1.
So LAHF is not invalid in some processor, e.g. Intel(R) Xeon(R) CPU X5460.
On such processor, the dr_save_arith_flags generates bad instruction.
We got to find another way to save arith flags efficiently.

Original issue: http://code.google.com/p/dynamorio/issues/detail?id=181

[derekbruening]

From qin.zhao@gmail.com on July 29, 2009 11:31:12

It is the same for SAHF

[derekbruening]

From qin.zhao@gmail.com on July 29, 2009 11:52:14

Intel(R) Xeon(R) CPU X5460 seems support LAHF and SAHF, but there are some processors
do not support LAHF/SAHF.

[derekbruening]

From derek.br...@gmail.com on July 29, 2009 12:01:49

This was PR 249775. DR already checks for this and aborts with a fatal error on a
processor that does not support lahf/sahf. Since AFAIK only very early Intel 64-bit
chips (and maybe early AMD64) did not support lahf and sahf we saw adding full
support as very low priority.

Labels: -Priority-Medium Priority-Low

[derekbruening]

From derek.br...@gmail.com on July 29, 2009 12:03:14

Did you actually hit a problem without hitting the fatal error? Then please fix the
checking code in proc_init().

[derekbruening]

From qin.zhao@gmail.com on September 29, 2009 10:30:48

Status: WontFix