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UefiCpuPkg/CpuExceptionHandlerLib: Setup single step in #PF handler

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Once the #PF handler has set the page to be 'present', there should
be a way to reset it to 'not-present'. 'TF' bit in EFLAGS can be used
for this purpose. 'TF' bit will be set in interrupted function context
so that it can be triggered once the cpu control returns back to the
instruction causing #PF and re-execute it.

This is an necessary step to implement non-stop mode for Heap Guard
and NULL Pointer Detection feature.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Jian J Wang
2018-08-09 16:17:19 +08:00
parent 8f2613628a
commit 16b918bbaf
3 changed files with 12 additions and 3 deletions
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4
UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ExceptionTssEntryAsm.nasm
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@@ -355,10 +355,8 @@ o16 mov [ecx + IA32_TSS._SS], ax
movzx ebx, word [ecx + IA32_TSS._CS]
mov [eax - 0x8], ebx ; create CS in old stack
mov ebx, dword [ecx + IA32_TSS.EFLAGS]
bts ebx, 8
bts ebx, 8 ; Set TF
mov [eax - 0x4], ebx ; create eflags in old stack
mov dword [ecx + IA32_TSS.EFLAGS], ebx ; update eflags in old TSS
mov eax, dword [ecx + IA32_TSS._ESP] ; Get old stack pointer
sub eax, 0xc ; minus 12 byte
mov dword [ecx + IA32_TSS._ESP], eax ; Set new stack pointer