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bangldayChinYikMing
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ubuntu
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Return -1 for syscall close on fd less than 3
Some user programs attempt to close stdout or stderr, but rv32emu relies on these file descriptors for logging and debugging. Allowing their closure could lead to unexpected behavior, making it difficult to trace emulator activity. This commit modifies the syscall close implementation to return -1 when attempting to close file descriptors less than 3. By ensuring these essential output channels remain open, rv32emu retains its ability to print logs and error messages. User programs receive a clear failure signal instead of silently closing critical streams. Close #435 Co-authored-by: ChinYikMing <[email protected]>
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5 files changed

+126
-95
lines changed

5 files changed

+126
-95
lines changed

‎src/emulate.c‎

Lines changed: 11 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1078,11 +1078,17 @@ void rv_step(void *arg)
10781078
assert(block->satp == rv->csr_satp);
10791079
#endif
10801080

1081-
/* After emulating the previous block, it is determined whether the
1082-
* branch is taken or not. The IR array of the current block is then
1083-
* assigned to either the branch_taken or branch_untaken pointer of
1084-
* the previous block.
1085-
*/
1081+
#if !RV32_HAS(SYSTEM)
1082+
/* on exit */
1083+
if (unlikely(block->ir_head->pc == PRIV(rv)->exit_addr))
1084+
PRIV(rv)->on_exit = true;
1085+
#endif
1086+
1087+
/* After emulating the previous block, it is determined whether the
1088+
* branch is taken or not. The IR array of the current block is then
1089+
* assigned to either the branch_taken or branch_untaken pointer of
1090+
* the previous block.
1091+
*/
10861092

10871093
#if RV32_HAS(BLOCK_CHAINING)
10881094
if (prev

‎src/riscv.c‎

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -261,7 +261,7 @@ static void map_file(char **ram_loc, const char *name)
261261
exit(EXIT_FAILURE);
262262
}
263263

264-
#define ALIGN_FDT(x) (((x) + (FDT_TAGSIZE) - 1) & ~((FDT_TAGSIZE) - 1))
264+
#define ALIGN_FDT(x) (((x) + (FDT_TAGSIZE) -1) & ~((FDT_TAGSIZE) -1))
265265
static char *realloc_property(char *fdt,
266266
int nodeoffset,
267267
const char *name,
@@ -434,6 +434,15 @@ riscv_t *rv_create(riscv_user_t rv_attr)
434434
if ((end = elf_get_symbol(elf, "_end")))
435435
attr->break_addr = end->st_value;
436436

437+
#if !RV32_HAS(SYSTEM)
438+
/* set not exiting */
439+
attr->on_exit = false;
440+
441+
const struct Elf32_Sym *exit;
442+
if ((exit = elf_get_symbol(elf, "exit")))
443+
attr->exit_addr = exit->st_value;
444+
#endif
445+
437446
assert(elf_load(elf, attr->mem));
438447

439448
/* set the entry pc */

‎src/riscv.h‎

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -548,6 +548,14 @@ typedef struct {
548548
/* the data segment break address */
549549
riscv_word_t break_addr;
550550

551+
#if !RV32_HAS(SYSTEM)
552+
/* the exit entry address */
553+
riscv_word_t exit_addr;
554+
555+
/* flag to determine if the emulator exits the target program */
556+
bool on_exit;
557+
#endif
558+
551559
/* SBI timer */
552560
uint64_t timer;
553561
} vm_attr_t;

‎src/rv32_template.c‎

Lines changed: 70 additions & 73 deletions
Original file line numberDiff line numberDiff line change
@@ -120,7 +120,10 @@
120120
*/
121121

122122
/* Internal */
123-
RVOP(nop, { rv->X[rv_reg_zero] = 0; }, GEN({/* no operation */}))
123+
RVOP(
124+
nop,
125+
{ rv->X[rv_reg_zero] = 0; },
126+
GEN({/* no operation */}))
124127

125128
/* LUI is used to build 32-bit constants and uses the U-type format. LUI
126129
* places the U-immediate value in the top 20 bits of the destination
@@ -364,78 +367,72 @@ RVOP(
364367
(type) x cond (type) y
365368
/* clang-format on */
366369

367-
#define BRANCH_FUNC(type, cond) \
368-
IIF(RV32_HAS(EXT_C))(, const uint32_t pc = PC;); \
369-
if (BRANCH_COND(type, rv->X[ir->rs1], rv->X[ir->rs2], cond)) { \
370-
IIF(RV32_HAS(SYSTEM)) \
371-
( \
372-
{ \
373-
if (!rv->is_trapped) { \
374-
is_branch_taken = false; \
375-
} \
376-
}, \
377-
is_branch_taken = false;); \
378-
struct rv_insn *untaken = ir->branch_untaken; \
379-
if (!untaken) \
380-
goto nextop; \
381-
IIF(RV32_HAS(JIT)) \
382-
( \
383-
{ \
384-
block_t *next = cache_get(rv->block_cache, PC + 4, true); \
385-
if (next IIF(RV32_HAS(SYSTEM))( \
386-
&&next->satp == rv->csr_satp, )) { \
387-
if (!set_add(&pc_set, PC + 4)) \
388-
has_loops = true; \
389-
if (cache_hot(rv->block_cache, PC + 4)) \
390-
goto nextop; \
391-
} \
392-
}, ); \
393-
PC += 4; \
394-
IIF(RV32_HAS(SYSTEM)) \
395-
( \
396-
{ \
397-
if (!rv->is_trapped) { \
398-
last_pc = PC; \
399-
MUST_TAIL return untaken->impl(rv, untaken, cycle, PC); \
400-
} \
401-
}, ); \
402-
goto end_op; \
403-
} \
404-
IIF(RV32_HAS(SYSTEM)) \
405-
( \
406-
{ \
407-
if (!rv->is_trapped) { \
408-
is_branch_taken = true; \
409-
} \
410-
}, \
411-
is_branch_taken = true;); \
412-
PC += ir->imm; \
413-
/* check instruction misaligned */ \
414-
IIF(RV32_HAS(EXT_C)) \
415-
(, RV_EXC_MISALIGN_HANDLER(pc, INSN, false, 0);); \
416-
struct rv_insn *taken = ir->branch_taken; \
417-
if (taken) { \
418-
IIF(RV32_HAS(JIT)) \
419-
( \
420-
{ \
421-
block_t *next = cache_get(rv->block_cache, PC, true); \
422-
if (next IIF(RV32_HAS(SYSTEM))( \
423-
&&next->satp == rv->csr_satp, )) { \
424-
if (!set_add(&pc_set, PC)) \
425-
has_loops = true; \
426-
if (cache_hot(rv->block_cache, PC)) \
427-
goto end_op; \
428-
} \
429-
}, ); \
430-
IIF(RV32_HAS(SYSTEM)) \
431-
( \
432-
{ \
433-
if (!rv->is_trapped) { \
434-
last_pc = PC; \
435-
MUST_TAIL return taken->impl(rv, taken, cycle, PC); \
436-
} \
437-
}, ); \
438-
} \
370+
#define BRANCH_FUNC(type, cond) \
371+
IIF(RV32_HAS(EXT_C))(, const uint32_t pc = PC;); \
372+
if (BRANCH_COND(type, rv->X[ir->rs1], rv->X[ir->rs2], cond)) { \
373+
IIF(RV32_HAS(SYSTEM)) \
374+
( \
375+
{ \
376+
if (!rv->is_trapped) { \
377+
is_branch_taken = false; \
378+
} \
379+
}, \
380+
is_branch_taken = false;); \
381+
struct rv_insn *untaken = ir->branch_untaken; \
382+
if (!untaken) \
383+
goto nextop; \
384+
IIF(RV32_HAS(JIT)) \
385+
({ \
386+
block_t *next = cache_get(rv->block_cache, PC + 4, true); \
387+
if (next IIF(RV32_HAS(SYSTEM))(&&next->satp == rv->csr_satp, )) { \
388+
if (!set_add(&pc_set, PC + 4)) \
389+
has_loops = true; \
390+
if (cache_hot(rv->block_cache, PC + 4)) \
391+
goto nextop; \
392+
} \
393+
}, ); \
394+
PC += 4; \
395+
IIF(RV32_HAS(SYSTEM)) \
396+
({ \
397+
if (!rv->is_trapped) { \
398+
last_pc = PC; \
399+
MUST_TAIL return untaken->impl(rv, untaken, cycle, PC); \
400+
} \
401+
}, ); \
402+
goto end_op; \
403+
} \
404+
IIF(RV32_HAS(SYSTEM)) \
405+
( \
406+
{ \
407+
if (!rv->is_trapped) { \
408+
is_branch_taken = true; \
409+
} \
410+
}, \
411+
is_branch_taken = true;); \
412+
PC += ir->imm; \
413+
/* check instruction misaligned */ \
414+
IIF(RV32_HAS(EXT_C)) \
415+
(, RV_EXC_MISALIGN_HANDLER(pc, INSN, false, 0);); \
416+
struct rv_insn *taken = ir->branch_taken; \
417+
if (taken) { \
418+
IIF(RV32_HAS(JIT)) \
419+
({ \
420+
block_t *next = cache_get(rv->block_cache, PC, true); \
421+
if (next IIF(RV32_HAS(SYSTEM))(&&next->satp == rv->csr_satp, )) { \
422+
if (!set_add(&pc_set, PC)) \
423+
has_loops = true; \
424+
if (cache_hot(rv->block_cache, PC)) \
425+
goto end_op; \
426+
} \
427+
}, ); \
428+
IIF(RV32_HAS(SYSTEM)) \
429+
({ \
430+
if (!rv->is_trapped) { \
431+
last_pc = PC; \
432+
MUST_TAIL return taken->impl(rv, taken, cycle, PC); \
433+
} \
434+
}, ); \
435+
} \
439436
goto end_op;
440437

441438
/* In RV32I and RV64I, if the branch is taken, set pc = pc + offset, where

‎src/syscall.c‎

Lines changed: 27 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -230,24 +230,35 @@ static void syscall_close(riscv_t *rv)
230230
/* _close(fd); */
231231
uint32_t fd = rv_get_reg(rv, rv_reg_a0);
232232

233-
if (fd >= 3) { /* lookup the file descriptor */
234-
map_iter_t it;
235-
map_find(attr->fd_map, &it, &fd);
236-
if (!map_at_end(attr->fd_map, &it)) {
237-
if (fclose(map_iter_value(&it, FILE *))) {
238-
/* error */
239-
rv_set_reg(rv, rv_reg_a0, -1);
240-
return;
241-
}
242-
map_erase(attr->fd_map, &it);
243-
244-
/* success */
245-
rv_set_reg(rv, rv_reg_a0, 0);
246-
}
233+
#if !RV32_HAS(SYSTEM)
234+
/*
235+
* The crt0 closes standard file descriptor(0, 1, 2) when
236+
* the process exits. Thus, the operations by the crt0
237+
* should not considered as error.
238+
*/
239+
if (fd < 3 && !PRIV(rv)->on_exit) {
240+
rv_set_reg(rv, rv_reg_a0, -1);
241+
rv_log_error(
242+
"Attempted to close a file descriptor < 3 (fd=%u). Operation "
243+
"not supported.",
244+
fd);
245+
return;
247246
}
247+
#endif
248248

249-
/* success */
250-
rv_set_reg(rv, rv_reg_a0, 0);
249+
map_iter_t it;
250+
map_find(attr->fd_map, &it, &fd);
251+
if (!map_at_end(attr->fd_map, &it)) {
252+
if (fclose(map_iter_value(&it, FILE *))) {
253+
/* error */
254+
rv_set_reg(rv, rv_reg_a0, -1);
255+
return;
256+
}
257+
map_erase(attr->fd_map, &it);
258+
259+
/* success */
260+
rv_set_reg(rv, rv_reg_a0, 0);
261+
}
251262
}
252263

253264
/* lseek() repositions the file offset of the open file description associated

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