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Linux/Documentation/arch/sparc/adi.rst

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Diff markup

Differences between /Documentation/arch/sparc/adi.rst (Version linux-6.12-rc7) and /Documentation/arch/m68k/adi.rst (Version linux-5.9.16)


  1 ================================                  
  2 Application Data Integrity (ADI)                  
  3 ================================                  
  4                                                   
  5 SPARC M7 processor adds the Application Data I    
  6 ADI allows a task to set version tags on any s    
  7 space. Once ADI is enabled and version tags ar    
  8 address space of a task, the processor will co    
  9 to memory in these ranges to the version set b    
 10 previously. Access to memory is granted only i    
 11 matches the tag set by the application. In cas    
 12 raises an exception.                              
 13                                                   
 14 Following steps must be taken by a task to ena    
 15                                                   
 16 1. Set the user mode PSTATE.mcde bit. This act    
 17    the task's entire address space to enable/d    
 18                                                   
 19 2. Set TTE.mcd bit on any TLB entries that cor    
 20    addresses ADI is being enabled on. MMU chec    
 21    on the pages that have TTE.mcd bit set.        
 22                                                   
 23 3. Set the version tag for virtual addresses u    
 24    and one of the MCD specific ASIs. Each stxa    
 25    given tag for one ADI block size number of     
 26    be repeated for entire page to set tags for    
 27                                                   
 28 ADI block size for the platform is provided by    
 29 in machine description tables. Hypervisor also    
 30 top bits in the virtual address that specify t    
 31 version tag has been set for a memory location    
 32 physical memory and the same tag must be prese    
 33 bits of the virtual address being presented to    
 34 SPARC M7 processor, MMU uses bits 63-60 for ve    
 35 size is same as cacheline size which is 64 byt    
 36 version to, say 10, on a range of memory, must    
 37 virtual addresses that contain 0xa in bits 63-    
 38                                                   
 39 ADI is enabled on a set of pages using mprotec    
 40 When ADI is enabled on a set of pages by a tas    
 41 kernel sets the PSTATE.mcde bit for the task.     
 42 addresses are set with an stxa instruction on     
 43 ASI_MCD_PRIMARY or ASI_MCD_ST_BLKINIT_PRIMARY.    
 44 provided by the hypervisor to the kernel.  Ker    
 45 ADI block size to userspace using auxiliary ve    
 46 info. Following auxiliary vectors are provided    
 47                                                   
 48         ============    ======================    
 49         AT_ADI_BLKSZ    ADI block size. This i    
 50                         alignment, in bytes, o    
 51         AT_ADI_NBITS    Number of ADI version     
 52         ============    ======================    
 53                                                   
 54                                                   
 55 IMPORTANT NOTES                                   
 56 ===============                                   
 57                                                   
 58 - Version tag values of 0x0 and 0xf are reserv    
 59   tag in virtual address and never generate a     
 60                                                   
 61 - Version tags are set on virtual addresses fr    
 62   tags are stored in physical memory. Tags are    
 63   after it has been allocated to a task and a     
 64   it.                                             
 65                                                   
 66 - When a task frees a memory page it had set v    
 67   goes back to free page pool. When this page     
 68   kernel clears the page using block initializ    
 69   version tags as well for the page. If a page    
 70   freed and allocated back to the same task, o    
 71   task on that page will no longer be present.    
 72                                                   
 73 - ADI tag mismatches are not detected for non-    
 74                                                   
 75 - Kernel does not set any tags for user pages     
 76   task's responsibility to set any version tag    
 77   version tags are preserved if a page is swap    
 78   swapped back in. It also preserves that vers    
 79   migrated.                                       
 80                                                   
 81 - ADI works for any size pages. A userspace ta    
 82   page size when using ADI. It can simply sele    
 83   range, enable ADI on the range using mprotec    
 84   for the entire range. mprotect() ensures ran    
 85   and is a multiple of page size.                 
 86                                                   
 87 - ADI tags can only be set on writable memory.    
 88   not be set on read-only mappings.               
 89                                                   
 90                                                   
 91                                                   
 92 ADI related traps                                 
 93 =================                                 
 94                                                   
 95 With ADI enabled, following new traps may occu    
 96                                                   
 97 Disrupting memory corruption                      
 98 ----------------------------                      
 99                                                   
100         When a store accesses a memory locatio    
101         the task is running with ADI enabled (    
102         tag in the address used (bits 63:60) d    
103         the corresponding cacheline, a memory     
104         default, it is a disrupting trap and i    
105         first. Hypervisor creates a sun4v erro    
106         resumable error (TT=0x7e) trap to the     
107         a SIGSEGV to the task that resulted in    
108         info::                                    
109                                                   
110                 siginfo.si_signo = SIGSEGV;       
111                 siginfo.errno = 0;                
112                 siginfo.si_code = SEGV_ADIDERR    
113                 siginfo.si_addr = addr; /* PC     
114                 siginfo.si_trapno = 0;            
115                                                   
116                                                   
117 Precise memory corruption                         
118 -------------------------                         
119                                                   
120         When a store accesses a memory locatio    
121         the task is running with ADI enabled (    
122         tag in the address used (bits 63:60) d    
123         the corresponding cacheline, a memory     
124         MCD precise exception is enabled (MCDP    
125         exception is sent to the kernel with T    
126         a SIGSEGV to the task that resulted in    
127         info::                                    
128                                                   
129                 siginfo.si_signo = SIGSEGV;       
130                 siginfo.errno = 0;                
131                 siginfo.si_code = SEGV_ADIPERR    
132                 siginfo.si_addr = addr; /* add    
133                 siginfo.si_trapno = 0;            
134                                                   
135         NOTE:                                     
136                 ADI tag mismatch on a load alw    
137                                                   
138                                                   
139 MCD disabled                                      
140 ------------                                      
141                                                   
142         When a task has not enabled ADI and at    
143         on a memory address, processor sends a    
144         trap is handled by hypervisor first an    
145         trap through to the kernel as Data Acc    
146         fault type set to 0xa (invalid ASI). W    
147         sends the task SIGSEGV signal with fol    
148                                                   
149                 siginfo.si_signo = SIGSEGV;       
150                 siginfo.errno = 0;                
151                 siginfo.si_code = SEGV_ACCADI;    
152                 siginfo.si_addr = addr; /* add    
153                 siginfo.si_trapno = 0;            
154                                                   
155                                                   
156 Sample program to use ADI                         
157 -------------------------                         
158                                                   
159 Following sample program is meant to illustrat    
160 functionality::                                   
161                                                   
162   #include <unistd.h>                             
163   #include <stdio.h>                              
164   #include <stdlib.h>                             
165   #include <elf.h>                                
166   #include <sys/ipc.h>                            
167   #include <sys/shm.h>                            
168   #include <sys/mman.h>                           
169   #include <asm/asi.h>                            
170                                                   
171   #ifndef AT_ADI_BLKSZ                            
172   #define AT_ADI_BLKSZ  48                        
173   #endif                                          
174   #ifndef AT_ADI_NBITS                            
175   #define AT_ADI_NBITS  49                        
176   #endif                                          
177                                                   
178   #ifndef PROT_ADI                                
179   #define PROT_ADI      0x10                      
180   #endif                                          
181                                                   
182   #define BUFFER_SIZE     32*1024*1024UL          
183                                                   
184   main(int argc, char* argv[], char* envp[])      
185   {                                               
186           unsigned long i, mcde, adi_blksz, ad    
187           char *shmaddr, *tmp_addr, *end, *ver    
188           int shmid, version;                     
189         Elf64_auxv_t *auxv;                       
190                                                   
191         adi_blksz = 0;                            
192                                                   
193         while(*envp++ != NULL);                   
194         for (auxv = (Elf64_auxv_t *)envp; auxv    
195                 switch (auxv->a_type) {           
196                 case AT_ADI_BLKSZ:                
197                         adi_blksz = auxv->a_un    
198                         break;                    
199                 case AT_ADI_NBITS:                
200                         adi_nbits = auxv->a_un    
201                         break;                    
202                 }                                 
203         }                                         
204         if (adi_blksz == 0) {                     
205                 fprintf(stderr, "Oops! ADI is     
206                 exit(1);                          
207         }                                         
208                                                   
209         printf("ADI capabilities:\n");            
210         printf("\tBlock size = %ld\n", adi_blk    
211         printf("\tNumber of bits = %ld\n", adi    
212                                                   
213           if ((shmid = shmget(2, BUFFER_SIZE,     
214                                   IPC_CREAT |     
215                   perror("shmget failed");        
216                   exit(1);                        
217           }                                       
218                                                   
219           shmaddr = shmat(shmid, NULL, 0);        
220           if (shmaddr == (char *)-1) {            
221                   perror("shm attach failed");    
222                   shmctl(shmid, IPC_RMID, NULL    
223                   exit(1);                        
224           }                                       
225                                                   
226         if (mprotect(shmaddr, BUFFER_SIZE, PRO    
227                 perror("mprotect failed");        
228                 goto err_out;                     
229         }                                         
230                                                   
231           /* Set the ADI version tag on the sh    
232            */                                     
233           version = 10;                           
234           tmp_addr = shmaddr;                     
235           end = shmaddr + BUFFER_SIZE;            
236           while (tmp_addr < end) {                
237                   asm volatile(                   
238                           "stxa %1, [%0]0x90\n    
239                           :                       
240                           : "r" (tmp_addr), "r    
241                   tmp_addr += adi_blksz;          
242           }                                       
243         asm volatile("membar #Sync\n\t");         
244                                                   
245           /* Create a versioned address from t    
246          * version tag in the upper adi_nbits     
247            */                                     
248           tmp_addr = (void *) ((unsigned long)    
249           tmp_addr = (void *) ((unsigned long)    
250           veraddr = (void *) (((unsigned long)    
251                           | (unsigned long)tmp    
252                                                   
253           printf("Starting the writes:\n");       
254           for (i = 0; i < BUFFER_SIZE; i++) {     
255                   veraddr[i] = (char)(i);         
256                   if (!(i % (1024 * 1024)))       
257                           printf(".");            
258           }                                       
259           printf("\n");                           
260                                                   
261           printf("Verifying data...");            
262         fflush(stdout);                           
263           for (i = 0; i < BUFFER_SIZE; i++)       
264                   if (veraddr[i] != (char)i)      
265                           printf("\nIndex %lu     
266           printf("Done.\n");                      
267                                                   
268           /* Disable ADI and clean up             
269            */                                     
270         if (mprotect(shmaddr, BUFFER_SIZE, PRO    
271                 perror("mprotect failed");        
272                 goto err_out;                     
273         }                                         
274                                                   
275           if (shmdt((const void *)shmaddr) !=     
276                   perror("Detach failure");       
277           shmctl(shmid, IPC_RMID, NULL);          
278                                                   
279           exit(0);                                
280                                                   
281   err_out:                                        
282           if (shmdt((const void *)shmaddr) !=     
283                   perror("Detach failure");       
284           shmctl(shmid, IPC_RMID, NULL);          
285           exit(1);                                
286   }                                               
                                                      

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