[reactos] 01/05: [FREELDR] Support setting up the EBP register on INT386() entry only if EBP != 0, otherwise use it only as output.

[Hermès Bélusca-Maïto]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=ff722ac72e98f320f27a0…

commit ff722ac72e98f320f27a0e57b4a5fb78753a2320
Author:     Hermès Bélusca-Maïto <hermes.belusca-maito(a)reactos.org>
AuthorDate: Sun Dec 22 13:53:17 2019 +0100
Commit:     Hermès Bélusca-Maïto <hermes.belusca-maito(a)reactos.org>
CommitDate: Mon Dec 23 21:06:40 2019 +0100

    [FREELDR] Support setting up the EBP register on INT386() entry only if EBP != 0,
otherwise use it only as output.
---
 boot/freeldr/freeldr/arch/amd64/int386.S      | 1 -
 boot/freeldr/freeldr/arch/i386/int386.S       | 1 +
 boot/freeldr/freeldr/arch/realmode/int386.inc | 9 ++++++++-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/boot/freeldr/freeldr/arch/amd64/int386.S
b/boot/freeldr/freeldr/arch/amd64/int386.S
index f3bd65a4da7..4e0dfa72d1b 100644
--- a/boot/freeldr/freeldr/arch/amd64/int386.S
+++ b/boot/freeldr/freeldr/arch/amd64/int386.S
@@ -45,7 +45,6 @@ Int386:
     sub rsp, 40
     //.ENDPROLOG
 
-int386_2:
     /* Copy the int vector to shared memory */
     mov dword ptr [BSS_IntVector], ecx
 
diff --git a/boot/freeldr/freeldr/arch/i386/int386.S
b/boot/freeldr/freeldr/arch/i386/int386.S
index e1c371956d5..295c47cc109 100644
--- a/boot/freeldr/freeldr/arch/i386/int386.S
+++ b/boot/freeldr/freeldr/arch/i386/int386.S
@@ -73,6 +73,7 @@ Int386_return:
     mov ecx, REGS_SIZE / 4
     rep movsd
 
+    /* Restore all registers + segment registers */
     popa
     pop gs
     pop fs
diff --git a/boot/freeldr/freeldr/arch/realmode/int386.inc
b/boot/freeldr/freeldr/arch/realmode/int386.inc
index 49a63eb9e37..ea3a822424d 100644
--- a/boot/freeldr/freeldr/arch/realmode/int386.inc
+++ b/boot/freeldr/freeldr/arch/realmode/int386.inc
@@ -37,13 +37,19 @@ Int386:
     mov ax, word ptr cs:[BSS_RegisterSet + REGS_GS]
     mov gs, ax
 
+    /* Setup ebp only if EBP != 0, otherwise use it only as output */
+    mov eax, dword ptr cs:[BSS_RegisterSet + REGS_EBP]
+    test eax, eax
+    jz Int386_set_registers
+    mov ebp, eax
+
+Int386_set_registers:
     mov eax, dword ptr cs:[BSS_RegisterSet + REGS_EAX]
     mov ebx, dword ptr cs:[BSS_RegisterSet + REGS_EBX]
     mov ecx, dword ptr cs:[BSS_RegisterSet + REGS_ECX]
     mov edx, dword ptr cs:[BSS_RegisterSet + REGS_EDX]
     mov esi, dword ptr cs:[BSS_RegisterSet + REGS_ESI]
     mov edi, dword ptr cs:[BSS_RegisterSet + REGS_EDI]
-    // Don't setup ebp, we only use it as output!
 
     /* Call the interrupt vector */
     /*int       Int386_vector*/
@@ -72,6 +78,7 @@ Int386_vector_opcode:
     pushfd
     pop dword ptr cs:[BSS_RegisterSet + REGS_EFLAGS]
 
+    /* Restore all registers + segment registers */
     popad
     pop gs
     pop fs