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scripts/qemu-gdb: Simplify fs_base fetching for coroutines

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There're a bunch of code trying to fetch fs_base in different ways.  IIUC
the simplest way instead is "$fs_base".  It also has the benefit that it'll
work for both live gdb session or coredumps.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-ID: <20241212204801.1420528-3-peterx@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Peter Xu 2024-12-12 15:48:00 -05:00 • committed by Kevin Wolf
parent 5bf10468b6
commit f4e343b655
1 changed files with 2 additions and 21 deletions
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23
scripts/qemugdb/coroutine.py
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@ -13,28 +13,9 @@ import gdb
VOID_PTR = gdb.lookup_type('void').pointer()
def get_fs_base():
'''Fetch %fs base value using arch_prctl(ARCH_GET_FS). This is
pthread_self().'''
# %rsp - 120 is scratch space according to the SystemV ABI
old = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)')
gdb.execute('call (int)arch_prctl(0x1003, $rsp - 120)', False, True)
fs_base = gdb.parse_and_eval('*(uint64_t*)($rsp - 120)')
gdb.execute('set *(uint64_t*)($rsp - 120) = %s' % old, False, True)
return fs_base
def pthread_self():
'''Fetch pthread_self() from the glibc start_thread function.'''
f = gdb.newest_frame()
while f.name() != 'start_thread':
f = f.older()
if f is None:
return get_fs_base()
try:
return f.read_var("arg")
except ValueError:
return get_fs_base()
'''Fetch the base address of TLS.'''
return gdb.parse_and_eval("$fs_base")
def get_glibc_pointer_guard():
'''Fetch glibc pointer guard value'''