From a6f99ace4014896f81a2f101416fd5413579f2bd Mon Sep 17 00:00:00 2001
From: Dmitry Vyukov <dvyukov@google.com>
Date: Fri, 28 Jun 2024 16:33:04 +0200
Subject: pkg/rpcserver: move kernel test/data range checks from executor

We see some errors of the form:

SYZFAIL: coverage filter is full
pc=0x80007000c0008 regions=[0xffffffffbfffffff 0x243fffffff 0x143fffffff 0xc3fffffff] alloc=156

Executor shouldn't send non kernel addresses in signal,
but somehow it does. It can happen if the VM memory is corrupted,
or if the test program does something very nasty (e.g. discovers
the output region and writes to it).

It's not possible to reliably filter signal in the tested VM.
Move all of the filtering logic to the host.

Fixes #4942
---
 executor/executor_linux.h | 78 -----------------------------------------------
 1 file changed, 78 deletions(-)

(limited to 'executor/executor_linux.h')

diff --git a/executor/executor_linux.h b/executor/executor_linux.h
index cb980838f..ff8f3bc60 100644
--- a/executor/executor_linux.h
+++ b/executor/executor_linux.h
@@ -36,8 +36,6 @@ struct kcov_remote_arg {
 #define KCOV_SUBSYSTEM_MASK (0xffull << 56)
 #define KCOV_INSTANCE_MASK (0xffffffffull)
 
-static bool is_gvisor;
-
 static inline __u64 kcov_remote_handle(__u64 subsys, __u64 inst)
 {
 	if (subsys & ~KCOV_SUBSYSTEM_MASK || inst & ~KCOV_INSTANCE_MASK)
@@ -45,14 +43,9 @@ static inline __u64 kcov_remote_handle(__u64 subsys, __u64 inst)
 	return subsys | inst;
 }
 
-static bool detect_kernel_bitness();
-static bool detect_gvisor();
-
 static void os_init(int argc, char** argv, char* data, size_t data_size)
 {
 	prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
-	is_kernel_64_bit = detect_kernel_bitness();
-	is_gvisor = detect_gvisor();
 	// Surround the main data mapping with PROT_NONE pages to make virtual address layout more consistent
 	// across different configurations (static/non-static build) and C repros.
 	// One observed case before: executor had a mapping above the data mapping (output region),
@@ -177,77 +170,6 @@ static void cover_collect(cover_t* cov)
 		cov->size = *(uint32*)cov->data;
 }
 
-static bool use_cover_edges(uint32 pc)
-{
-	return true;
-}
-
-static bool is_kernel_data(uint64 addr)
-{
-	if (is_gvisor)
-		return false;
-#if GOARCH_386 || GOARCH_amd64
-	// This range corresponds to the first 1TB of the physical memory mapping,
-	// see Documentation/arch/x86/x86_64/mm.rst.
-	return addr >= 0xffff880000000000ull && addr < 0xffff890000000000ull;
-#else
-	return false;
-#endif
-}
-
-// Returns >0 for yes, <0 for no, 0 for don't know.
-static int is_kernel_pc(uint64 pc)
-{
-	if (is_gvisor)
-		return 0;
-#if GOARCH_386 || GOARCH_amd64
-	// Text/modules range for x86_64.
-	return pc >= 0xffffffff80000000ull && pc < 0xffffffffff000000ull ? 1 : -1;
-#else
-	return 0;
-#endif
-}
-
-static bool use_cover_edges(uint64 pc)
-{
-#if GOARCH_amd64 || GOARCH_arm64
-	if (is_gvisor)
-		return false; // gvisor coverage is not a trace, so producing edges won't work
-#endif
-	return true;
-}
-
-static bool detect_kernel_bitness()
-{
-	if (sizeof(void*) == 8)
-		return true;
-	// It turns out to be surprisingly hard to understand if the kernel underneath is 64-bits.
-	// A common method is to look at uname.machine. But it is produced in some involved ways,
-	// and we will need to know about all strings it returns and in the end it can be overriden
-	// during build and lie (and there are known precedents of this).
-	// So instead we look at size of addresses in /proc/kallsyms.
-	bool wide = true;
-	int fd = open("/proc/kallsyms", O_RDONLY);
-	if (fd != -1) {
-		char buf[16];
-		if (read(fd, buf, sizeof(buf)) == sizeof(buf) &&
-		    (buf[8] == ' ' || buf[8] == '\t'))
-			wide = false;
-		close(fd);
-	}
-	debug("detected %d-bit kernel\n", wide ? 64 : 32);
-	return wide;
-}
-
-static bool detect_gvisor()
-{
-	char buf[64] = {};
-	// 3 stands for undeclared SYSLOG_ACTION_READ_ALL.
-	syscall(__NR_syslog, 3, buf, sizeof(buf) - 1);
-	// This is a first line of gvisor dmesg.
-	return strstr(buf, "Starting gVisor");
-}
-
 // One does not simply exit.
 // _exit can in fact fail.
 // syzkaller did manage to generate a seccomp filter that prohibits exit_group syscall.
-- 
cgit mrf-deployment