[PATCH] ShellPkg/dmem: Only dump sizeof (EFI_SYSTEM_TABLE) bytes for gST

[Ruiyu Ni <ruiyu.ni@intel.com>]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1236

When "dmem" runs without additional arguments, it dumps the memory
content of EFI_SYSTEM_TABLE. But today's implementation dumps 512
bytes. It's not correct because sizeof (EFI_SYSTEM_TABLE) is less
than 512, the 512-read causes page fault exception in a heap-guard
enabled environment.

The patch changes the implementation to only dump
sizeof (EFI_SYSTEM_TABLE) bytes for gST.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
---
 ShellPkg/Library/UefiShellDebug1CommandsLib/Dmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ShellPkg/Library/UefiShellDebug1CommandsLib/Dmem.c b/ShellPkg/Library/UefiShellDebug1CommandsLib/Dmem.c
index f38593a9e9..a4c18c9b68 100644
--- a/ShellPkg/Library/UefiShellDebug1CommandsLib/Dmem.c
+++ b/ShellPkg/Library/UefiShellDebug1CommandsLib/Dmem.c
@@ -149,7 +149,7 @@ ShellCommandRunDmem (
       Temp1 = ShellCommandLineGetRawValue(Package, 1);
       if (Temp1 == NULL) {
         Address = gST;
-        Size = 512;
+        Size    = sizeof (*gST);
       } else {
         if (!ShellIsHexOrDecimalNumber(Temp1, TRUE, FALSE) || EFI_ERROR(ShellConvertStringToUint64(Temp1, (UINT64*)&Address, TRUE, FALSE))) {
           ShellPrintHiiEx(-1, -1, NULL, STRING_TOKEN (STR_GEN_PARAM_INV), gShellDebug1HiiHandle, L"dmem", Temp1);
-- 
2.16.1.windows.1