From 3caaaddffd605c0ec1787d68295b732fff73026b Mon Sep 17 00:00:00 2001 From: Andrei Vagin Date: Tue, 29 Sep 2020 04:45:55 +0000 Subject: runtime: don't crash if vsyscall and vdso are disabled on x86_64 If vdso is disabled, the goruntime calls gettimeofday from vsyscall, but if vsyscall is disabled too, all golang binaries crash: SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0xffffffffff600000} --- killed by SIGSEGV (core dumped) ++ vsyscall doesn't work as it was designed for a long time due to security reasons and now vsyscall is a little more expensive than real syscalls: https://github.com/torvalds/linux/commit/5cec93c216db This patch reworks the code to call syscalls if the vdso library isn't available. Change-Id: I16cbf3f49871bea91e26af1f49aa0ae2fbd3a01d GitHub-Last-Rev: 1d133cd30a5dee1fea9aee0fb4ea0b07e0e87f2a GitHub-Pull-Request: golang/go#41681 Reviewed-on: https://go-review.googlesource.com/c/go/+/257982 Run-TryBot: Tobias Klauser TryBot-Result: Go Bot Reviewed-by: Ian Lance Taylor Reviewed-by: Michael Pratt Trust: Michael Pratt --- src/syscall/asm_linux_amd64.s | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'src/syscall/asm_linux_amd64.s') diff --git a/src/syscall/asm_linux_amd64.s b/src/syscall/asm_linux_amd64.s index 2c3374338f..ba22179dc2 100644 --- a/src/syscall/asm_linux_amd64.s +++ b/src/syscall/asm_linux_amd64.s @@ -9,6 +9,8 @@ // System calls for AMD64, Linux // +#define SYS_gettimeofday 96 + // func Syscall(trap int64, a1, a2, a3 uintptr) (r1, r2, err uintptr); // Trap # in AX, args in DI SI DX R10 R8 R9, return in AX DX // Note that this differs from "standard" ABI convention, which @@ -144,13 +146,19 @@ TEXT ·gettimeofday(SB),NOSPLIT,$0-16 MOVQ tv+0(FP), DI MOVQ $0, SI MOVQ runtime·vdsoGettimeofdaySym(SB), AX + TESTQ AX, AX + JZ fallback CALL AX - +ret: CMPQ AX, $0xfffffffffffff001 JLS ok7 NEGQ AX MOVQ AX, err+8(FP) RET +fallback: + MOVL $SYS_gettimeofday, AX + SYSCALL + JMP ret ok7: MOVQ $0, err+8(FP) RET -- cgit v1.3