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sh: Teach the DWARF unwinder about modules

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Pass a module's .eh_frame section to the DWARF unwinder at module load
time so that the section's FDEs and CIEs can be registered with the
DWARF unwinder. This allows us to unwind the stack through module code
when generating backtraces.

Signed-off-by: Matt Fleming <matt@console-pimps.org>
This commit is contained in:
Matt Fleming
2009-10-09 23:20:54 +01:00
parent c153a58e71
commit a6a2f2ad67
3 changed files with 175 additions and 53 deletions
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181
arch/sh/kernel/dwarf.c
View File

@ -655,7 +655,7 @@ bail:
}
static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
unsigned char *end)
unsigned char *end, struct module *mod)
{
struct dwarf_cie *cie;
unsigned long flags;
@ -751,6 +751,8 @@ static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
cie->initial_instructions = p;
cie->instructions_end = end;
cie->mod = mod;
/* Add to list */
spin_lock_irqsave(&dwarf_cie_lock, flags);
list_add_tail(&cie->link, &dwarf_cie_list);
@ -761,7 +763,7 @@ static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
static int dwarf_parse_fde(void *entry, u32 entry_type,
void *start, unsigned long len,
unsigned char *end)
unsigned char *end, struct module *mod)
{
struct dwarf_fde *fde;
struct dwarf_cie *cie;
@ -810,6 +812,8 @@ static int dwarf_parse_fde(void *entry, u32 entry_type,
fde->instructions = p;
fde->end = end;
fde->mod = mod;
/* Add to list. */
spin_lock_irqsave(&dwarf_fde_lock, flags);
list_add_tail(&fde->link, &dwarf_fde_list);
@ -874,6 +878,124 @@ static void dwarf_unwinder_cleanup(void)
kmem_cache_destroy(dwarf_frame_cachep);
}
/**
* dwarf_parse_section - parse DWARF section
* @eh_frame_start: start address of the .eh_frame section
* @eh_frame_end: end address of the .eh_frame section
* @mod: the kernel module containing the .eh_frame section
*
* Parse the information in a .eh_frame section.
*/
int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
struct module *mod)
{
u32 entry_type;
void *p, *entry;
int count, err;
unsigned long len;
unsigned int c_entries, f_entries;
unsigned char *end;
c_entries = 0;
f_entries = 0;
entry = eh_frame_start;
while ((char *)entry < eh_frame_end) {
p = entry;
count = dwarf_entry_len(p, &len);
if (count == 0) {
/*
* We read a bogus length field value. There is
* nothing we can do here apart from disabling
* the DWARF unwinder. We can't even skip this
* entry and move to the next one because 'len'
* tells us where our next entry is.
*/
err = -EINVAL;
goto out;
} else
p += count;
/* initial length does not include itself */
end = p + len;
entry_type = get_unaligned((u32 *)p);
p += 4;
if (entry_type == DW_EH_FRAME_CIE) {
err = dwarf_parse_cie(entry, p, len, end, mod);
if (err < 0)
goto out;
else
c_entries++;
} else {
err = dwarf_parse_fde(entry, entry_type, p, len,
end, mod);
if (err < 0)
goto out;
else
f_entries++;
}
entry = (char *)entry + len + 4;
}
printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
c_entries, f_entries);
return 0;
out:
return err;
}
/**
* dwarf_module_unload - remove FDE/CIEs associated with @mod
* @mod: the module that is being unloaded
*
* Remove any FDEs and CIEs from the global lists that came from
* @mod's .eh_frame section because @mod is being unloaded.
*/
void dwarf_module_unload(struct module *mod)
{
struct dwarf_fde *fde;
struct dwarf_cie *cie;
unsigned long flags;
spin_lock_irqsave(&dwarf_cie_lock, flags);
again_cie:
list_for_each_entry(cie, &dwarf_cie_list, link) {
if (cie->mod == mod)
break;
}
if (&cie->link != &dwarf_cie_list) {
list_del(&cie->link);
kfree(cie);
goto again_cie;
}
spin_unlock_irqrestore(&dwarf_cie_lock, flags);
spin_lock_irqsave(&dwarf_fde_lock, flags);
again_fde:
list_for_each_entry(fde, &dwarf_fde_list, link) {
if (fde->mod == mod)
break;
}
if (&fde->link != &dwarf_fde_list) {
list_del(&fde->link);
kfree(fde);
goto again_fde;
}
spin_unlock_irqrestore(&dwarf_fde_lock, flags);
}
/**
* dwarf_unwinder_init - initialise the dwarf unwinder
*
@ -885,19 +1007,10 @@ static void dwarf_unwinder_cleanup(void)
*/
static int __init dwarf_unwinder_init(void)
{
u32 entry_type;
void *p, *entry;
int count, err;
unsigned long len;
unsigned int c_entries, f_entries;
unsigned char *end;
int err;
INIT_LIST_HEAD(&dwarf_cie_list);
INIT_LIST_HEAD(&dwarf_fde_list);
c_entries = 0;
f_entries = 0;
entry = &__start_eh_frame;
dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
sizeof(struct dwarf_frame), 0, SLAB_PANIC, NULL);
dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
@ -913,47 +1026,9 @@ static int __init dwarf_unwinder_init(void)
mempool_free_slab,
dwarf_reg_cachep);
while ((char *)entry < __stop_eh_frame) {
p = entry;
count = dwarf_entry_len(p, &len);
if (count == 0) {
/*
* We read a bogus length field value. There is
* nothing we can do here apart from disabling
* the DWARF unwinder. We can't even skip this
* entry and move to the next one because 'len'
* tells us where our next entry is.
*/
goto out;
} else
p += count;
/* initial length does not include itself */
end = p + len;
entry_type = get_unaligned((u32 *)p);
p += 4;
if (entry_type == DW_EH_FRAME_CIE) {
err = dwarf_parse_cie(entry, p, len, end);
if (err < 0)
goto out;
else
c_entries++;
} else {
err = dwarf_parse_fde(entry, entry_type, p, len, end);
if (err < 0)
goto out;
else
f_entries++;
}
entry = (char *)entry + len + 4;
}
printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
c_entries, f_entries);
err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
if (err)
goto out;
err = unwinder_register(&dwarf_unwinder);
if (err)