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runtime: look up funcInfo by func pointer

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runtime.Func.{Name,FileLine} need to be able to
go from a *_func to a funcInfo. The missing bit of
information is what module contains that *_func.

The existing implementation looked up the module
using the *_func's entry PC. A subsequent change will
store *_func's entry PC relative to the containing module.
Change the module lookup to instead for the module
whose pclntable contains the *_func,
cutting all dependencies on the contents of the *_func.

Change-Id: I2dbbfec043ebc2e9a6ef19bbdec623ac84353b10
Reviewed-on: https://go-review.googlesource.com/c/go/+/351458
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Josh Bleecher Snyder 2021-09-21 12:18:38 -07:00
parent f961d8e5b1
commit e54843f2f4
1 changed files with 16 additions and 1 deletions
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17
src/runtime/symtab.go
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@ -273,7 +273,22 @@ func (f *Func) raw() *_func {
func (f *Func) funcInfo() funcInfo {
fn := f.raw()
return funcInfo{fn, findmoduledatap(fn.entry)}
// Find the module containing fn. fn is located in the pclntable.
// The unsafe.Pointer to uintptr conversions and arithmetic
// are safe because we are working with module addresses.
ptr := uintptr(unsafe.Pointer(fn))
var mod *moduledata
for datap := &firstmoduledata; datap != nil; datap = datap.next {
if len(datap.pclntable) == 0 {
continue
}
base := uintptr(unsafe.Pointer(&datap.pclntable[0]))
if base <= ptr && ptr < base+uintptr(len(datap.pclntable)) {
mod = datap
break
}
}
return funcInfo{fn, mod}
}
// PCDATA and FUNCDATA table indexes.