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[src/trunk]: src/sys/arch/amd64/amd64 Restore the ability to debug a 32 bit p...



details:   https://anonhg.NetBSD.org/src/rev/c5d93074995d
branches:  trunk
changeset: 452653:c5d93074995d
user:      christos <christos%NetBSD.org@localhost>
date:      Sat Jul 20 18:25:11 2019 +0000

description:
Restore the ability to debug a 32 bit process from a 64 bit debugger:
- add a function to validate a 64 bit context in 32 bit mode to write registers
- remove 32 bit checks from read and write register functions
- check for pc to fit in 32 bits.
proposed in tech-kern, ok maxv.

diffstat:

 sys/arch/amd64/amd64/netbsd32_machdep.c |   28 +++++-
 sys/arch/amd64/amd64/process_machdep.c  |  140 +++++++++++++++----------------
 2 files changed, 92 insertions(+), 76 deletions(-)

diffs (truncated from 304 to 300 lines):

diff -r 6b3ddfa265e8 -r c5d93074995d sys/arch/amd64/amd64/netbsd32_machdep.c
--- a/sys/arch/amd64/amd64/netbsd32_machdep.c   Sat Jul 20 18:23:05 2019 +0000
+++ b/sys/arch/amd64/amd64/netbsd32_machdep.c   Sat Jul 20 18:25:11 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: netbsd32_machdep.c,v 1.124 2019/06/26 12:30:12 mgorny Exp $    */
+/*     $NetBSD: netbsd32_machdep.c,v 1.125 2019/07/20 18:25:11 christos Exp $  */
 
 /*
  * Copyright (c) 2001 Wasabi Systems, Inc.
@@ -36,7 +36,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: netbsd32_machdep.c,v 1.124 2019/06/26 12:30:12 mgorny Exp $");
+__KERNEL_RCSID(0, "$NetBSD: netbsd32_machdep.c,v 1.125 2019/07/20 18:25:11 christos Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_compat_netbsd.h"
@@ -382,7 +382,7 @@
        regs->r_esp = tf->tf_rsp & 0xffffffff;
        regs->r_ss = tf->tf_ss & 0xffff;
 
-       return (0);
+       return 0;
 }
 
 int
@@ -987,6 +987,25 @@
        return 0;
 }
 
+static int
+cpu_mcontext32from64_validate(struct lwp *l, const struct reg *regp)
+{
+       mcontext32_t mc;
+       __greg32_t *gr32 = mc.__gregs;
+       const __greg_t *gr = regp->regs;
+
+       memset(&mc, 0, sizeof(mc));
+       gr32[_REG32_EFL] = gr[_REG_RFLAGS];
+       gr32[_REG32_EIP] = gr[_REG_RIP];
+       gr32[_REG32_CS] = gr[_REG_CS];
+       gr32[_REG32_DS] = gr[_REG_DS];
+       gr32[_REG32_ES] = gr[_REG_ES];
+       gr32[_REG32_FS] = gr[_REG_FS];
+       gr32[_REG32_GS] = gr[_REG_GS];
+       gr32[_REG32_SS] = gr[_REG_SS];
+       return cpu_mcontext32_validate(l, &mc);
+}
+
 vaddr_t
 netbsd32_vm_default_addr(struct proc *p, vaddr_t base, vsize_t sz,
     int topdown)
@@ -1009,6 +1028,8 @@
 {
 
        MODULE_HOOK_SET(netbsd32_machine32_hook, "mach32", netbsd32_machine32);
+       MODULE_HOOK_SET(netbsd32_reg_validate_hook,
+           "mcontext32from64_validate", cpu_mcontext32from64_validate);
 }
 
 void
@@ -1016,4 +1037,5 @@
 {
 
        MODULE_HOOK_UNSET(netbsd32_machine32_hook);
+       MODULE_HOOK_UNSET(netbsd32_reg_validate_hook);
 }
diff -r 6b3ddfa265e8 -r c5d93074995d sys/arch/amd64/amd64/process_machdep.c
--- a/sys/arch/amd64/amd64/process_machdep.c    Sat Jul 20 18:23:05 2019 +0000
+++ b/sys/arch/amd64/amd64/process_machdep.c    Sat Jul 20 18:25:11 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: process_machdep.c,v 1.41 2019/06/27 01:59:30 christos Exp $    */
+/*     $NetBSD: process_machdep.c,v 1.42 2019/07/20 18:25:11 christos Exp $    */
 
 /*
  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
@@ -74,7 +74,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: process_machdep.c,v 1.41 2019/06/27 01:59:30 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: process_machdep.c,v 1.42 2019/07/20 18:25:11 christos Exp $");
 
 #include "opt_xen.h"
 #include <sys/param.h>
@@ -83,6 +83,7 @@
 #include <sys/kernel.h>
 #include <sys/proc.h>
 #include <sys/ptrace.h>
+#include <sys/compat_stub.h>
 
 #include <uvm/uvm_extern.h>
 
@@ -103,42 +104,48 @@
 }
 
 int
-process_read_regs(struct lwp *l, struct reg *regs)
+process_read_regs(struct lwp *l, struct reg *regp)
 {
        struct trapframe *tf = process_frame(l);
-       struct proc *p = l->l_proc;
-
-       if (p->p_flag & PK_32) {
-               return EINVAL;
-       }
+       long *regs = regp->regs;
+       const bool pk32 = (l->l_proc->p_flag & PK_32) != 0;
 
-       regs->regs[_REG_RDI] = tf->tf_rdi;
-       regs->regs[_REG_RSI] = tf->tf_rsi;
-       regs->regs[_REG_RDX] = tf->tf_rdx;
-       regs->regs[_REG_R10] = tf->tf_r10;
-       regs->regs[_REG_R8]  = tf->tf_r8;
-       regs->regs[_REG_R9]  = tf->tf_r9;
+       regs[_REG_RDI] = tf->tf_rdi;
+       regs[_REG_RSI] = tf->tf_rsi;
+       regs[_REG_RDX] = tf->tf_rdx;
+       regs[_REG_R10] = tf->tf_r10;
+       regs[_REG_R8]  = tf->tf_r8;
+       regs[_REG_R9]  = tf->tf_r9;
        /* argX not touched */
-       regs->regs[_REG_RCX] = tf->tf_rcx;
-       regs->regs[_REG_R11] = tf->tf_r11;
-       regs->regs[_REG_R12] = tf->tf_r12;
-       regs->regs[_REG_R13] = tf->tf_r13;
-       regs->regs[_REG_R14] = tf->tf_r14;
-       regs->regs[_REG_R15] = tf->tf_r15;
-       regs->regs[_REG_RBP] = tf->tf_rbp;
-       regs->regs[_REG_RBX] = tf->tf_rbx;
-       regs->regs[_REG_RAX] = tf->tf_rax;
-       regs->regs[_REG_GS]  = 0;
-       regs->regs[_REG_FS]  = 0;
-       regs->regs[_REG_ES]  = GSEL(GUDATA_SEL, SEL_UPL);
-       regs->regs[_REG_DS]  = GSEL(GUDATA_SEL, SEL_UPL);
-       regs->regs[_REG_TRAPNO] = tf->tf_trapno;
-       regs->regs[_REG_ERR] = tf->tf_err;
-       regs->regs[_REG_RIP] = tf->tf_rip;
-       regs->regs[_REG_CS]  = LSEL(LUCODE_SEL, SEL_UPL);
-       regs->regs[_REG_RFLAGS] = tf->tf_rflags;
-       regs->regs[_REG_RSP] = tf->tf_rsp;
-       regs->regs[_REG_SS]  = LSEL(LUDATA_SEL, SEL_UPL);
+       regs[_REG_RCX] = tf->tf_rcx;
+       regs[_REG_R11] = tf->tf_r11;
+       regs[_REG_R12] = tf->tf_r12;
+       regs[_REG_R13] = tf->tf_r13;
+       regs[_REG_R14] = tf->tf_r14;
+       regs[_REG_R15] = tf->tf_r15;
+       regs[_REG_RBP] = tf->tf_rbp;
+       regs[_REG_RBX] = tf->tf_rbx;
+       regs[_REG_RAX] = tf->tf_rax;
+       if (pk32) {
+               regs[_REG_GS] = tf->tf_gs & 0xffff;
+               regs[_REG_FS] = tf->tf_fs & 0xffff;
+               regs[_REG_ES] = tf->tf_es & 0xffff;
+               regs[_REG_DS] = tf->tf_ds & 0xffff;
+               regs[_REG_CS] = tf->tf_cs & 0xffff;
+               regs[_REG_SS] = tf->tf_ss & 0xffff;
+       } else {
+               regs[_REG_GS] = 0;
+               regs[_REG_FS] = 0;
+               regs[_REG_ES] = GSEL(GUDATA_SEL, SEL_UPL);
+               regs[_REG_DS] = GSEL(GUDATA_SEL, SEL_UPL);
+               regs[_REG_CS] = LSEL(LUCODE_SEL, SEL_UPL);
+               regs[_REG_SS] = LSEL(LUDATA_SEL, SEL_UPL);
+       }
+       regs[_REG_TRAPNO] = tf->tf_trapno;
+       regs[_REG_ERR] = tf->tf_err;
+       regs[_REG_RIP] = tf->tf_rip;
+       regs[_REG_RFLAGS] = tf->tf_rflags;
+       regs[_REG_RSP] = tf->tf_rsp;
 
        return 0;
 }
@@ -146,11 +153,6 @@
 int
 process_read_fpregs(struct lwp *l, struct fpreg *regs, size_t *sz)
 {
-       struct proc *p = l->l_proc;
-
-       if (p->p_flag & PK_32) {
-               return EINVAL;
-       }
 
        process_read_fpregs_xmm(l, &regs->fxstate);
 
@@ -160,11 +162,6 @@
 int
 process_read_dbregs(struct lwp *l, struct dbreg *regs, size_t *sz)
 {
-       struct proc *p = l->l_proc;
-
-       if (p->p_flag & PK_32) {
-               return EINVAL;
-       }
 
        x86_dbregs_read(l, regs);
 
@@ -175,19 +172,20 @@
 process_write_regs(struct lwp *l, const struct reg *regp)
 {
        struct trapframe *tf = process_frame(l);
-       struct proc *p = l->l_proc;
        int error;
        const long *regs = regp->regs;
-
-       if (p->p_flag & PK_32) {
-               return EINVAL;
-       }
+       const bool pk32 = (l->l_proc->p_flag & PK_32) != 0;
 
        /*
         * Check for security violations. Note that struct regs is compatible
         * with the __gregs array in mcontext_t.
         */
-       error = cpu_mcontext_validate(l, (const mcontext_t *)regs);
+       if (pk32) {
+               MODULE_HOOK_CALL(netbsd32_reg_validate_hook, (l, regp), EINVAL,
+                   error);
+       } else {
+               error = cpu_mcontext_validate(l, (const mcontext_t *)regs);
+       }
        if (error != 0)
                return error;
 
@@ -207,16 +205,25 @@
        tf->tf_rbp  = regs[_REG_RBP];
        tf->tf_rbx  = regs[_REG_RBX];
        tf->tf_rax  = regs[_REG_RAX];
-       tf->tf_gs   = 0;
-       tf->tf_fs   = 0;
-       tf->tf_es   = GSEL(GUDATA_SEL, SEL_UPL);
-       tf->tf_ds   = GSEL(GUDATA_SEL, SEL_UPL);
+       if (pk32) {
+               tf->tf_gs = regs[_REG_GS] & 0xffff;
+               tf->tf_fs = regs[_REG_FS] & 0xffff;
+               tf->tf_es = regs[_REG_ES] & 0xffff;
+               tf->tf_ds = regs[_REG_DS] & 0xffff;
+               tf->tf_cs = regs[_REG_CS] & 0xffff;
+               tf->tf_ss = regs[_REG_SS] & 0xffff;
+       } else {
+               tf->tf_gs = 0;
+               tf->tf_fs = 0;
+               tf->tf_es = GSEL(GUDATA_SEL, SEL_UPL);
+               tf->tf_ds = GSEL(GUDATA_SEL, SEL_UPL);
+               tf->tf_cs = LSEL(LUCODE_SEL, SEL_UPL);
+               tf->tf_ss = LSEL(LUDATA_SEL, SEL_UPL);
+       }
        /* trapno, err not touched */
        tf->tf_rip  = regs[_REG_RIP];
-       tf->tf_cs   = LSEL(LUCODE_SEL, SEL_UPL);
        tf->tf_rflags = regs[_REG_RFLAGS];
        tf->tf_rsp  = regs[_REG_RSP];
-       tf->tf_ss   = LSEL(LUDATA_SEL, SEL_UPL);
 
 #ifdef XENPV
        /* see comment in cpu_setmcontext */
@@ -230,11 +237,6 @@
 int
 process_write_fpregs(struct lwp *l, const struct fpreg *regs, size_t sz)
 {
-       struct proc *p = l->l_proc;
-
-       if (p->p_flag & PK_32) {
-               return EINVAL;
-       }
 
        process_write_fpregs_xmm(l, &regs->fxstate);
        return 0;
@@ -243,13 +245,8 @@
 int
 process_write_dbregs(struct lwp *l, const struct dbreg *regs, size_t sz)
 {
-       struct proc *p = l->l_proc;
        int error;
 
-       if (p->p_flag & PK_32) {
-               return EINVAL;
-       }
-
        /*
         * Check for security violations.
         */
@@ -279,15 +276,12 @@
 process_set_pc(struct lwp *l, void *addr)
 {
        struct trapframe *tf = process_frame(l);
-       struct proc *p = l->l_proc;
+       const bool pk32 = (l->l_proc->p_flag & PK_32) != 0;
+       const uint64_t rip = (uint64_t)addr;
 
-       if (p->p_flag & PK_32) {
+       if (rip >= (pk32 ? VM_MAXUSER_ADDRESS32 : VM_MAXUSER_ADDRESS))
                return EINVAL;
-       }
-
-       if ((uint64_t)addr >= VM_MAXUSER_ADDRESS)
-               return EINVAL;
-       tf->tf_rip = (uint64_t)addr;



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