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instrs: Check SREG validity using modreg table

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This commit is contained in:
Alexis Engelke
2020-11-29 11:53:06 +01:00
parent 13e7e27640
commit aa1a39bd9d
3 changed files with 14 additions and 7 deletions
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6
decode.c
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@@ -89,11 +89,7 @@ decode_modrm(const uint8_t* buffer, int len, DecodeMode mode, FdInstr* instr,
reg_idx += prefixes & PREFIX_REXR ? 8 : 0;
#endif
if (is_seg && reg_idx >= 6)
return FD_ERR_UD;
else if (UNLIKELY(instr->type == FDI_MOV_G2S) && reg_idx == 1)
return FD_ERR_UD;
else if (is_cr && (~0x011d >> reg_idx) & 1)
if (is_cr && (~0x011d >> reg_idx) & 1)
return FD_ERR_UD;
else if (is_dr && reg_idx >= 8)
return FD_ERR_UD;

13
instrs.txt
View File

@@ -139,9 +139,18 @@
89 MR GP GP - - MOV
8a RM GP GP - - MOV SIZE_8
8b RM GP GP - - MOV
8c MR GP16 SREG - - MOV_S2G
8c/0 MR GP16 SREG - - MOV_S2G
8c/1 MR GP16 SREG - - MOV_S2G
8c/2 MR GP16 SREG - - MOV_S2G
8c/3 MR GP16 SREG - - MOV_S2G
8c/4 MR GP16 SREG - - MOV_S2G
8c/5 MR GP16 SREG - - MOV_S2G
8d/m RM GP MEMZ - - LEA
8e RM SREG GP16 - - MOV_G2S
8e/0 RM SREG GP16 - - MOV_G2S
8e/2 RM SREG GP16 - - MOV_G2S
8e/3 RM SREG GP16 - - MOV_G2S
8e/4 RM SREG GP16 - - MOV_G2S
8e/5 RM SREG GP16 - - MOV_G2S
8f/0 M GP - - - POP DEF64
# Against frequent belief, only, XCHG (r/e)AX, (r)AX with 90 is NOP.
# As a lacking REX.B cannot be specified here, this is hardcoded.

2
tests/test_decode.c
View File

@@ -104,6 +104,8 @@ main(int argc, char** argv)
TEST64("\x44\x0f\x21\x00", "UD"); // dr8
TEST("\x8c\xc0", "[MOV_S2G reg2:r0 reg2:r0]");
TEST64("\x44\x8c\xc0", "[MOV_S2G reg2:r0 reg2:r0]");
TEST64("\x44\x8c\xf0", "UD"); // no segment register 6
TEST64("\x44\x8c\xf8", "UD"); // no segment register 7
TEST("\x8e\xc0", "[MOV_G2S reg2:r0 reg2:r0]");
TEST("\x8e\xc8", "UD"); // No mov cs, eax
TEST("\xd8\xc1", "[FADD reg0:r0 reg0:r1]");