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runtime: clear frame pointer at thread entry points

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There are a few places in the runtime where new threads enter Go code
with a possibly invalid frame pointer. mstart is the entry point for new
Ms, and rt0_go is the entrypoint for the program. As we try to introduce
frame pointer unwinding in more places (e.g. for heap profiling in CL
540476 or for execution trace events on the system stack in CL 593835),
we see these functions on the stack. We need to ensure that they have
valid frame pointers. These functions are both considered the "top"
(first) frame frame of the call stack, so this CL sets the frame pointer
register to 0 in these functions.

Updates #63630

Change-Id: I6a6a6964a9ebc6f68ba23d2616e5fb6f19677f97
Reviewed-on: https://go-review.googlesource.com/c/go/+/721020
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
Nick Ripley 2025-11-17 11:47:20 -05:00 • committed by Gopher Robot
parent 6919858338
commit eda2e8c683
2 changed files with 30 additions and 0 deletions
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15
src/runtime/asm_amd64.s
View file

@ -181,6 +181,14 @@ TEXT runtime·rt0_go(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
MOVQ AX, 24(SP) MOVQ AX, 24(SP)
MOVQ BX, 32(SP) MOVQ BX, 32(SP)
// This is typically the entry point for Go programs.
// Call stack unwinding must not proceed past this frame.
// Set the frame pointer register to 0 so that frame pointer-based unwinders
// (which don't use debug info for performance reasons)
// won't attempt to unwind past this function.
// See go.dev/issue/63630
MOVQ $0, BP
// create istack out of the given (operating system) stack. // create istack out of the given (operating system) stack.
// _cgo_init may update stackguard. // _cgo_init may update stackguard.
MOVQ $runtime·g0(SB), DI MOVQ $runtime·g0(SB), DI
@ -408,6 +416,13 @@ TEXT runtime·asminit(SB),NOSPLIT,$0-0
RET RET
TEXT runtime·mstart(SB),NOSPLIT|TOPFRAME|NOFRAME,$0 TEXT runtime·mstart(SB),NOSPLIT|TOPFRAME|NOFRAME,$0
// This is the root frame of new Go-created OS threads.
// Call stack unwinding must not proceed past this frame.
// Set the frame pointer register to 0 so that frame pointer-based unwinders
// (which don't use debug info for performance reasons)
// won't attempt to unwind past this function.
// See go.dev/issue/63630
MOVD $0, BP
CALL runtime·mstart0(SB) CALL runtime·mstart0(SB)
RET // not reached RET // not reached

15
src/runtime/asm_arm64.s
View file

@ -109,6 +109,14 @@ TEXT runtime·rt0_go(SB),NOSPLIT|TOPFRAME,$0
MOVW R0, 8(RSP) // argc MOVW R0, 8(RSP) // argc
MOVD R1, 16(RSP) // argv MOVD R1, 16(RSP) // argv
// This is typically the entry point for Go programs.
// Call stack unwinding must not proceed past this frame.
// Set the frame pointer register to 0 so that frame pointer-based unwinders
// (which don't use debug info for performance reasons)
// won't attempt to unwind past this function.
// See go.dev/issue/63630
MOVD $0, R29
#ifdef TLS_darwin #ifdef TLS_darwin
// Initialize TLS. // Initialize TLS.
MOVD ZR, g // clear g, make sure it's not junk. MOVD ZR, g // clear g, make sure it's not junk.
@ -248,6 +256,13 @@ TEXT runtime·asminit(SB),NOSPLIT|NOFRAME,$0-0
RET RET
TEXT runtime·mstart(SB),NOSPLIT|TOPFRAME,$0 TEXT runtime·mstart(SB),NOSPLIT|TOPFRAME,$0
// This is the root frame of new Go-created OS threads.
// Call stack unwinding must not proceed past this frame.
// Set the frame pointer register to 0 so that frame pointer-based unwinders
// (which don't use debug info for performance reasons)
// won't attempt to unwind past this function.
// See go.dev/issue/63630
MOVD $0, R29
BL runtime·mstart0(SB) BL runtime·mstart0(SB)
RET // not reached RET // not reached