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lguest: decode mmio accesses for PCI in example launcher.
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We don't do anything with them yet (emulate_mmio_write and
emulate_mmio_read are stubs), but we decode the instructions and
search for the device they're hitting.

Signed-off-by: Rusty Russell <[email protected]>
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@rustyrussell
rustyrussell committed Feb 11, 2015
1 parent 0a6bcc1 commit 6a54f9a
Showing 1 changed file with 167 additions and 0 deletions.
167 changes: 167 additions & 0 deletions tools/lguest/lguest.c
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Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,9 @@ static int lguest_fd;
/* a per-cpu variable indicating whose vcpu is currently running */
static unsigned int __thread cpu_id;

/* 5 bit device number in the PCI_CONFIG_ADDR => 32 only */
#define MAX_PCI_DEVICES 32

/* This is our list of devices. */
struct device_list {
/* Counter to assign interrupt numbers. */
Expand All @@ -114,6 +117,9 @@ struct device_list {
struct device *dev;
/* And a pointer to the last device for easy append. */
struct device *lastdev;

/* PCI devices. */
struct device *pci[MAX_PCI_DEVICES];
};

/* The list of Guest devices, based on command line arguments. */
Expand All @@ -140,6 +146,10 @@ struct device {
/* Is it operational */
bool running;

/* PCI MMIO resources (all in BAR0) */
size_t mmio_size;
u32 mmio_addr;

/* Device-specific data. */
void *priv;
};
Expand Down Expand Up @@ -1197,6 +1207,77 @@ static void setreg_off(size_t offset, u32 val)
err(1, "Setting register %u", offset);
}

/* Get register by instruction encoding */
static u32 getreg_num(unsigned regnum, u32 mask)
{
/* 8 bit ops use regnums 4-7 for high parts of word */
if (mask == 0xFF && (regnum & 0x4))
return getreg_num(regnum & 0x3, 0xFFFF) >> 8;

switch (regnum) {
case 0: return getreg(eax) & mask;
case 1: return getreg(ecx) & mask;
case 2: return getreg(edx) & mask;
case 3: return getreg(ebx) & mask;
case 4: return getreg(esp) & mask;
case 5: return getreg(ebp) & mask;
case 6: return getreg(esi) & mask;
case 7: return getreg(edi) & mask;
}
abort();
}

/* Set register by instruction encoding */
static void setreg_num(unsigned regnum, u32 val, u32 mask)
{
/* Don't try to set bits out of range */
assert(~(val & ~mask));

/* 8 bit ops use regnums 4-7 for high parts of word */
if (mask == 0xFF && (regnum & 0x4)) {
/* Construct the 16 bits we want. */
val = (val << 8) | getreg_num(regnum & 0x3, 0xFF);
setreg_num(regnum & 0x3, val, 0xFFFF);
return;
}

switch (regnum) {
case 0: setreg(eax, val | (getreg(eax) & ~mask)); return;
case 1: setreg(ecx, val | (getreg(ecx) & ~mask)); return;
case 2: setreg(edx, val | (getreg(edx) & ~mask)); return;
case 3: setreg(ebx, val | (getreg(ebx) & ~mask)); return;
case 4: setreg(esp, val | (getreg(esp) & ~mask)); return;
case 5: setreg(ebp, val | (getreg(ebp) & ~mask)); return;
case 6: setreg(esi, val | (getreg(esi) & ~mask)); return;
case 7: setreg(edi, val | (getreg(edi) & ~mask)); return;
}
abort();
}

/* Get bytes of displacement appended to instruction, from r/m encoding */
static u32 insn_displacement_len(u8 mod_reg_rm)
{
/* Switch on the mod bits */
switch (mod_reg_rm >> 6) {
case 0:
/* If mod == 0, and r/m == 101, 16-bit displacement follows */
if ((mod_reg_rm & 0x7) == 0x5)
return 2;
/* Normally, mod == 0 means no literal displacement */
return 0;
case 1:
/* One byte displacement */
return 1;
case 2:
/* Four byte displacement */
return 4;
case 3:
/* Register mode */
return 0;
}
abort();
}

static void emulate_insn(const u8 insn[])
{
unsigned long args[] = { LHREQ_TRAP, 13 };
Expand Down Expand Up @@ -1310,6 +1391,88 @@ static void emulate_insn(const u8 insn[])
err(1, "Reinjecting trap 13 for fault at %#x", getreg(eip));
}

static struct device *find_mmio_region(unsigned long paddr, u32 *off)
{
unsigned int i;

for (i = 1; i < MAX_PCI_DEVICES; i++) {
struct device *d = devices.pci[i];

if (!d)
continue;
if (paddr < d->mmio_addr)
continue;
if (paddr >= d->mmio_addr + d->mmio_size)
continue;
*off = paddr - d->mmio_addr;
return d;
}
return NULL;
}

static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask)
{
}

static u32 emulate_mmio_read(struct device *d, u32 off, u32 mask)
{
return 0xFFFFFFFF;
}

static void emulate_mmio(unsigned long paddr, const u8 *insn)
{
u32 val, off, mask = 0xFFFFFFFF, insnlen = 0;
struct device *d = find_mmio_region(paddr, &off);
unsigned long args[] = { LHREQ_TRAP, 14 };

if (!d) {
warnx("MMIO touching %#08lx (not a device)", paddr);
goto reinject;
}

/* Prefix makes it a 16 bit op */
if (insn[0] == 0x66) {
mask = 0xFFFF;
insnlen++;
}

/* iowrite */
if (insn[insnlen] == 0x89) {
/* Next byte is r/m byte: bits 3-5 are register. */
val = getreg_num((insn[insnlen+1] >> 3) & 0x7, mask);
emulate_mmio_write(d, off, val, mask);
insnlen += 2 + insn_displacement_len(insn[insnlen+1]);
} else if (insn[insnlen] == 0x8b) { /* ioread */
/* Next byte is r/m byte: bits 3-5 are register. */
val = emulate_mmio_read(d, off, mask);
setreg_num((insn[insnlen+1] >> 3) & 0x7, val, mask);
insnlen += 2 + insn_displacement_len(insn[insnlen+1]);
} else if (insn[0] == 0x88) { /* 8-bit iowrite */
mask = 0xff;
/* Next byte is r/m byte: bits 3-5 are register. */
val = getreg_num((insn[1] >> 3) & 0x7, mask);
emulate_mmio_write(d, off, val, mask);
insnlen = 2 + insn_displacement_len(insn[1]);
} else if (insn[0] == 0x8a) { /* 8-bit ioread */
mask = 0xff;
val = emulate_mmio_read(d, off, mask);
setreg_num((insn[1] >> 3) & 0x7, val, mask);
insnlen = 2 + insn_displacement_len(insn[1]);
} else {
warnx("Unknown MMIO instruction touching %#08lx:"
" %02x %02x %02x %02x at %u",
paddr, insn[0], insn[1], insn[2], insn[3], getreg(eip));
reinject:
/* Inject trap into Guest. */
if (write(lguest_fd, args, sizeof(args)) < 0)
err(1, "Reinjecting trap 14 for fault at %#x",
getreg(eip));
return;
}

/* Finally, we've "done" the instruction, so move past it. */
setreg(eip, getreg(eip) + insnlen);
}

/*L:190
* Device Setup
Expand Down Expand Up @@ -2004,6 +2167,10 @@ static void __attribute__((noreturn)) run_guest(void)
verbose("Emulating instruction at %#x\n",
getreg(eip));
emulate_insn(notify.insn);
} else if (notify.trap == 14) {
verbose("Emulating MMIO at %#x\n",
getreg(eip));
emulate_mmio(notify.addr, notify.insn);
} else
errx(1, "Unknown trap %i addr %#08x\n",
notify.trap, notify.addr);
Expand Down

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