From cf4912ae570ceae019b344785e4eeaf8cf273df3 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Fri, 11 May 2018 00:45:55 +0100 Subject: [PATCH] gdb/x86: Fix write out of mxcsr register for xsave targets In commit: commit 8ee22052f690c007556b97eed59f49350ece5ca9 Author: Andrew Burgess Date: Thu May 3 17:46:14 2018 +0100 gdb/x86: Handle kernels using compact xsave format in two places FXSAVE_ADDR was used instead of FXSAVE_MXCSR_ADDR to get the address of the mxcsr register within the xsave buffer. This will mean we are potentially accessing the wrong location within the xsave buffer. There are no tests included with this patch. The first mistake would only trigger an issue if/when the user tries to manually set the mxcsr register to a value that matches the random (value off stack) value that is in the xsave buffer, in this case the change by the user will go unnoticed by GDB, and the default value of mxcsr will be preserved. The second mistake only happens on the code path where all x87 registers are being written out of the register cache. I'm not sure how to trigger that code path. gdb/ChangeLog: * i387-tdep.c (i387_collect_xsave): Use FXSAVE_MXCSR_ADDR not FXSAVE_ADDR for the mxcsr register. --- gdb/ChangeLog | 5 +++++ gdb/i387-tdep.c | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index a3a133c036..67610d7144 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2018-05-11 Andrew Burgess + + * i387-tdep.c (i387_collect_xsave): Use FXSAVE_MXCSR_ADDR not + FXSAVE_ADDR for the mxcsr register. + 2018-05-11 Max Filippov * configure.tgt (xtensa*-*-linux*): Drop gdb_target definition. diff --git a/gdb/i387-tdep.c b/gdb/i387-tdep.c index aca70c186f..3effc35b17 100644 --- a/gdb/i387-tdep.c +++ b/gdb/i387-tdep.c @@ -1490,7 +1490,7 @@ i387_collect_xsave (const struct regcache *regcache, int regnum, require clearing. */ if ((clear_bv & (X86_XSTATE_AVX | X86_XSTATE_SSE)) == (X86_XSTATE_AVX | X86_XSTATE_SSE)) - store_unsigned_integer (FXSAVE_ADDR (tdep, regs, i), 2, byte_order, + store_unsigned_integer (FXSAVE_MXCSR_ADDR (regs), 2, byte_order, I387_MXCSR_INIT_VAL); if ((clear_bv & X86_XSTATE_X87)) @@ -1643,7 +1643,7 @@ i387_collect_xsave (const struct regcache *regcache, int regnum, { i = I387_MXCSR_REGNUM (tdep); regcache_raw_collect (regcache, i, raw); - p = FXSAVE_ADDR (tdep, regs, i); + p = FXSAVE_MXCSR_ADDR (regs); if (memcmp (raw, p, 4)) { /* Now, we need to mark one of either SSE of AVX as enabled. -- 2.34.1