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Groups > linux.kernel > #1715522
| From | Ricardo Neri <ricardo.neri-calderon@linux.intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v8 17/28] x86/insn-eval: Incorporate segment base in linear address computation |
| Date | 2017-08-19 02:30 +0200 |
| Message-ID | <ufZOi-2z5-15@gated-at.bofh.it> (permalink) |
| References | <ufZOh-2z5-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
insn_get_addr_ref() returns the effective address as defined by the
section 3.7.5.1 Vol 1 of the Intel 64 and IA-32 Architectures Software
Developer's Manual. In order to compute the linear address, we must add
to the effective address the segment base address as set in the segment
descriptor. The segment descriptor to use depends on the register used as
operand and segment override prefixes, if any.
In most cases, the segment base address will be 0 if the USER_DS/USER32_DS
segment is used or if segmentation is not used. However, the base address
is not necessarily zero if a user programs defines its own segments. This
is possible by using a local descriptor table.
Since the effective address is a signed quantity, the unsigned segment
base address is saved in a separate variable and added to the final,
unsigned, effective address.
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
arch/x86/lib/insn-eval.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 04f696c3793e..8ae110a273de 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -673,7 +673,7 @@ int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs)
void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
{
int addr_offset, base_offset, indx_offset;
- unsigned long linear_addr;
+ unsigned long linear_addr, seg_base_addr;
long eff_addr, base, indx;
insn_byte_t sib;
@@ -687,6 +687,10 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
goto out_err;
eff_addr = regs_get_register(regs, addr_offset);
+
+ seg_base_addr = insn_get_seg_base(regs, insn, addr_offset);
+ if (seg_base_addr == -1L)
+ goto out_err;
} else {
if (insn->sib.nbytes) {
/*
@@ -712,6 +716,11 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
indx = regs_get_register(regs, indx_offset);
eff_addr = base + indx * (1 << X86_SIB_SCALE(sib));
+
+ seg_base_addr = insn_get_seg_base(regs, insn,
+ base_offset);
+ if (seg_base_addr == -1L)
+ goto out_err;
} else {
addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
@@ -730,12 +739,17 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
} else {
eff_addr = regs_get_register(regs, addr_offset);
}
+
+ seg_base_addr = insn_get_seg_base(regs, insn,
+ addr_offset);
+ if (seg_base_addr == -1L)
+ goto out_err;
}
eff_addr += insn->displacement.value;
}
- linear_addr = (unsigned long)eff_addr;
+ linear_addr = (unsigned long)eff_addr + seg_base_addr;
return (void __user *)linear_addr;
out_err:
--
2.13.0
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[PATCH v8 00/28] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:30 +0200 [PATCH v8 18/28] x86/insn-eval: Add support to resolve 32-bit address encodings Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:30 +0200 [PATCH v8 04/28] uprobes/x86: Use existing definitions for segment override prefixes Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:30 +0200 [PATCH v8 17/28] x86/insn-eval: Incorporate segment base in linear address computation Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:30 +0200 [PATCH v8 08/28] x86/mpx, x86/insn: Relocate insn util functions to a new insn-eval file Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:30 +0200 [PATCH v8 10/28] x86/insn-eval: Add a utility function to get register offsets Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:30 +0200 [PATCH v8 19/28] x86/insn-eval: Add wrapper function for 32 and 64-bit addresses Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 20/28] x86/insn-eval: Handle 32-bit address encodings in virtual-8086 mode Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 15/28] x86/insn-eval: Add function to get default params of code segment Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 05/28] x86/mpx: Use signed variables to compute effective addresses Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 16/28] x86/insn-eval: Indicate a 32-bit displacement if ModRM.mod is 0 and ModRM.rm is 101b Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 13/28] x86/insn-eval: Add utility function to get segment descriptor Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 03/28] ptrace,x86: Make user_64bit_mode() available to 32-bit builds Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 23/28] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 28/28] selftests/x86: Add tests for instruction str and sldt Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 21/28] x86/insn-eval: Add support to resolve 16-bit addressing encodings Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 12/28] x86/insn-eval: Add utility functions to get segment selector Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 01/28] x86/mm: Relocate page fault error codes to traps.h Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 27/28] selftests/x86: Add tests for User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 24/28] x86/umip: Force a page fault when unable to copy emulated result to user Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 26/28] x86/traps: Fixup general protection faults caused by UMIP Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 07/28] x86/mpx: Do not use SIB.base if its value is 101b and ModRM.mod = 0 Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 22/28] x86/cpufeature: Add User-Mode Instruction Prevention definitions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 06/28] x86/mpx: Do not use SIB.index if its value is 100b and ModRM.mod is not 11b Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 14/28] x86/insn-eval: Add utility functions to get segment descriptor base address and limit Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 25/28] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200 [PATCH v8 09/28] x86/insn-eval: Do not BUG on invalid register type Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-08-19 02:40 +0200
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