libmach: implement register fetch for 32-bit x86 kernel

Also use memmove to silence some gcc warnings.

Fixes #1036.

R=r, EtherealMachine
CC=golang-dev
https://golang.org/cl/1943049

diff --git a/src/libmach/linux.c b/src/libmach/linux.c
index 46724b87e2fb1c8dc994cce8a659520080be83d7..8ddcea8cd14c2d50957e3b72008541dd114f9aa7 100644 (file)
--- a/src/libmach/linux.c
+++ b/src/libmach/linux.c
@@ -759,9 +759,9 @@ ptracerw(int type, int xtype, int isr, int pid, uvlong addr, void *v, uint n)
                        if(errno)
                                goto ptraceerr;
                        if(n-i >= sizeof(uintptr))
-                               *(uintptr*)((char*)v+i) = u;
+                               memmove((char*)v+i, &u, sizeof(uintptr));
                        else{
-                               *(uintptr*)buf = u;
+                               memmove(buf, &u, sizeof u);
                                memmove((char*)v+i, buf, n-i);
                        }
                }else{
@@ -772,9 +772,9 @@ ptracerw(int type, int xtype, int isr, int pid, uvlong addr, void *v, uint n)
                                u = ptrace(xtype, pid, addr+i, 0);
                                if(errno)
                                        return -1;
-                               *(uintptr*)buf = u;
+                               memmove(buf, &u, sizeof u);
                                memmove(buf, (char*)v+i, n-i);
-                               u = *(uintptr*)buf;
+                               memmove(&u, buf, sizeof u);
                        }
                        if(ptrace(type, pid, addr+i, u) < 0)
                                goto ptraceerr;
@@ -810,9 +810,22 @@ ptracesegrw(Map *map, Seg *seg, uvlong addr, void *v, uint n, int isr)
 // Go 32-bit is
 //     DI SI BP NSP BX DX CX AX GS FS ES DS TRAP ECODE PC CS EFLAGS SP SS
 
-// uint go32tolinux32tab[] = {
-//     4, 3, 5, 15, 0, 2, 1, 6, 10, 9, 8, 7, -1, -1, 12, 13, 14, 15, 16
-// };
+uint go32tolinux32tab[] = {
+       4, 3, 5, 15, 0, 2, 1, 6, 10, 9, 8, 7, -1, -1, 12, 13, 14, 15, 16
+};
+static int
+go32tolinux32(uvlong addr)
+{
+       int r;
+
+       if(addr%4 || addr/4 >= nelem(go32tolinux32tab))
+               return -1;
+       r = go32tolinux32tab[addr/4];
+       if(r < 0)
+               return -1;
+       return r*4;
+}
+
 uint go32tolinux64tab[] = {
        14, 13, 4, 19, 5, 12, 11, 10, 26, 25, 24, 23, -1, -1, 16, 17, 18, 19, 20
 };
@@ -830,15 +843,24 @@ go32tolinux64(uvlong addr)
 }
 
 extern Mach mi386;
+extern Mach mamd64;
 
 static int
 go2linux(uvlong addr)
 {
-       // TODO(rsc): If this file is being compiled in 32-bit mode,
-       // need to use the go32tolinux32 table instead.
+       if(sizeof(void*) == 4) {
+               if(mach == &mi386)
+                       return go32tolinux32(addr);
+               werrstr("unsupported architecture");
+               return -1;
+       }
 
        if(mach == &mi386)
                return go32tolinux64(addr);
+       if(mach != &mamd64) {
+               werrstr("unsupported architecture");
+               return -1;
+       }
 
        switch(addr){
        case offsetof(Ureg64, ax):