diff options
author | Joerg Roedel <jroedel@suse.de> | 2020-09-07 15:15:10 +0200 |
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committer | Borislav Petkov <bp@suse.de> | 2020-09-07 19:45:24 +0200 |
commit | 172639d79977ca7b5ce6f84f6606262f4081718f (patch) | |
tree | b54aa0ee26b44a3ab481810342049c92c112b1ce /arch/x86/lib/insn-eval.c | |
parent | 172b75e56b08846e6fb07a88e5685ce4e24f4620 (diff) | |
download | linux-172639d79977ca7b5ce6f84f6606262f4081718f.tar.bz2 |
x86/umip: Factor out instruction decoding
Factor out the code used to decode an instruction with the correct
address and operand sizes to a helper function.
No functional changes.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-10-joro@8bytes.org
Diffstat (limited to 'arch/x86/lib/insn-eval.c')
-rw-r--r-- | arch/x86/lib/insn-eval.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 947b7f1a0042..2323c85132cf 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -1405,3 +1405,48 @@ int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE]) return MAX_INSN_SIZE - not_copied; } + +/** + * insn_decode() - Decode an instruction + * @insn: Structure to store decoded instruction + * @regs: Structure with register values as seen when entering kernel mode + * @buf: Buffer containing the instruction bytes + * @buf_size: Number of instruction bytes available in buf + * + * Decodes the instruction provided in buf and stores the decoding results in + * insn. Also determines the correct address and operand sizes. + * + * Returns: + * + * True if instruction was decoded, False otherwise. + */ +bool insn_decode(struct insn *insn, struct pt_regs *regs, + unsigned char buf[MAX_INSN_SIZE], int buf_size) +{ + int seg_defs; + + insn_init(insn, buf, buf_size, user_64bit_mode(regs)); + + /* + * Override the default operand and address sizes with what is specified + * in the code segment descriptor. The instruction decoder only sets + * the address size it to either 4 or 8 address bytes and does nothing + * for the operand bytes. This OK for most of the cases, but we could + * have special cases where, for instance, a 16-bit code segment + * descriptor is used. + * If there is an address override prefix, the instruction decoder + * correctly updates these values, even for 16-bit defaults. + */ + seg_defs = insn_get_code_seg_params(regs); + if (seg_defs == -EINVAL) + return false; + + insn->addr_bytes = INSN_CODE_SEG_ADDR_SZ(seg_defs); + insn->opnd_bytes = INSN_CODE_SEG_OPND_SZ(seg_defs); + + insn_get_length(insn); + if (buf_size < insn->length) + return false; + + return true; +} |