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accel/tcg: Return -1 for execution from MMIO regions in get_page_addr_code()

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Now that all the callers can handle get_page_addr_code() returning -1,
remove all the code which tries to handle execution from MMIO regions
or small-MMU-region RAM areas. This will mean that we can correctly
execute from these areas, rather than ending up either aborting QEMU
or delivering an incorrect guest exception.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180710160013.26559-6-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2018-08-14 17:17:19 +01:00
parent 9739e3767a
commit 20cb6ae472
1 changed files with 10 additions and 85 deletions
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95
accel/tcg/cputlb.c
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@ -741,39 +741,6 @@ void tlb_set_page(CPUState *cpu, target_ulong vaddr,
prot, mmu_idx, size);
}
static void report_bad_exec(CPUState *cpu, target_ulong addr)
{
/* Accidentally executing outside RAM or ROM is quite common for
* several user-error situations, so report it in a way that
* makes it clear that this isn't a QEMU bug and provide suggestions
* about what a user could do to fix things.
*/
error_report("Trying to execute code outside RAM or ROM at 0x"
TARGET_FMT_lx, addr);
error_printf("This usually means one of the following happened:\n\n"
"(1) You told QEMU to execute a kernel for the wrong machine "
"type, and it crashed on startup (eg trying to run a "
"raspberry pi kernel on a versatilepb QEMU machine)\n"
"(2) You didn't give QEMU a kernel or BIOS filename at all, "
"and QEMU executed a ROM full of no-op instructions until "
"it fell off the end\n"
"(3) Your guest kernel has a bug and crashed by jumping "
"off into nowhere\n\n"
"This is almost always one of the first two, so check your "
"command line and that you are using the right type of kernel "
"for this machine.\n"
"If you think option (3) is likely then you can try debugging "
"your guest with the -d debug options; in particular "
"-d guest_errors will cause the log to include a dump of the "
"guest register state at this point.\n\n"
"Execution cannot continue; stopping here.\n\n");
/* Report also to the logs, with more detail including register dump */
qemu_log_mask(LOG_GUEST_ERROR, "qemu: fatal: Trying to execute code "
"outside RAM or ROM at 0x" TARGET_FMT_lx "\n", addr);
log_cpu_state_mask(LOG_GUEST_ERROR, cpu, CPU_DUMP_FPU | CPU_DUMP_CCOP);
}
static inline ram_addr_t qemu_ram_addr_from_host_nofail(void *ptr)
{
ram_addr_t ram_addr;
@ -963,7 +930,6 @@ tb_page_addr_t get_page_addr_code(CPUArchState *env, target_ulong addr)
MemoryRegionSection *section;
CPUState *cpu = ENV_GET_CPU(env);
CPUIOTLBEntry *iotlbentry;
hwaddr physaddr, mr_offset;
index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
mmu_idx = cpu_mmu_index(env, true);
@ -977,65 +943,24 @@ tb_page_addr_t get_page_addr_code(CPUArchState *env, target_ulong addr)
if (unlikely(env->tlb_table[mmu_idx][index].addr_code & TLB_RECHECK)) {
/*
* This is a TLB_RECHECK access, where the MMU protection
* covers a smaller range than a target page, and we must
* repeat the MMU check here. This tlb_fill() call might
* longjump out if this access should cause a guest exception.
*/
int index;
target_ulong tlb_addr;
tlb_fill(cpu, addr, 0, MMU_INST_FETCH, mmu_idx, 0);
index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
tlb_addr = env->tlb_table[mmu_idx][index].addr_code;
if (!(tlb_addr & ~(TARGET_PAGE_MASK | TLB_RECHECK))) {
/* RAM access. We can't handle this, so for now just stop */
cpu_abort(cpu, "Unable to handle guest executing from RAM within "
"a small MPU region at 0x" TARGET_FMT_lx, addr);
}
/*
* Fall through to handle IO accesses (which will almost certainly
* also result in failure)
* covers a smaller range than a target page. Return -1 to
* indicate that we cannot simply execute from RAM here;
* we will perform the necessary repeat of the MMU check
* when the "execute a single insn" code performs the
* load of the guest insn.
*/
return -1;
}
iotlbentry = &env->iotlb[mmu_idx][index];
section = iotlb_to_section(cpu, iotlbentry->addr, iotlbentry->attrs);
mr = section->mr;
if (memory_region_is_unassigned(mr)) {
qemu_mutex_lock_iothread();
if (memory_region_request_mmio_ptr(mr, addr)) {
qemu_mutex_unlock_iothread();
/* A MemoryRegion is potentially added so re-run the
* get_page_addr_code.
*/
return get_page_addr_code(env, addr);
}
qemu_mutex_unlock_iothread();
/* Give the new-style cpu_transaction_failed() hook first chance
* to handle this.
* This is not the ideal place to detect and generate CPU
* exceptions for instruction fetch failure (for instance
* we don't know the length of the access that the CPU would
* use, and it would be better to go ahead and try the access
* and use the MemTXResult it produced). However it is the
* simplest place we have currently available for the check.
/*
* Not guest RAM, so there is no ram_addr_t for it. Return -1,
* and we will execute a single insn from this device.
*/
mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr;
physaddr = mr_offset +
section->offset_within_address_space -
section->offset_within_region;
cpu_transaction_failed(cpu, physaddr, addr, 0, MMU_INST_FETCH, mmu_idx,
iotlbentry->attrs, MEMTX_DECODE_ERROR, 0);
cpu_unassigned_access(cpu, addr, false, true, 0, 4);
/* The CPU's unassigned access hook might have longjumped out
* with an exception. If it didn't (or there was no hook) then
* we can't proceed further.
*/
report_bad_exec(cpu, addr);
exit(1);
return -1;
}
p = (void *)((uintptr_t)addr + env->tlb_table[mmu_idx][index].addend);
return qemu_ram_addr_from_host_nofail(p);