Date: Fri, 26 May 2023 15:43:57 GMT From: Christos Margiolis <christos@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 5c134fba225f - main - kinst: fix memcpy() tracing crash Message-ID: <202305261543.34QFhvsM069265@gitrepo.freebsd.org>
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The branch main has been updated by christos: URL: https://cgit.FreeBSD.org/src/commit/?id=5c134fba225fabb2e0f9c763aaca0eeee81d8f9f commit 5c134fba225fabb2e0f9c763aaca0eeee81d8f9f Author: Christos Margiolis <christos@FreeBSD.org> AuthorDate: 2023-05-26 15:43:37 +0000 Commit: Christos Margiolis <christos@FreeBSD.org> CommitDate: 2023-05-26 15:43:37 +0000 kinst: fix memcpy() tracing crash Tracing memcpy() would crash the kernel, because we'd also trace the memcpy() calls from kinst_invop(). To fix this, introduce kinst_memcpy() whose arguments are 'volatile', so that we avoid having the compiler replace it with a regular memcpy(). Reviewed by: markj Approved by: markj (mentor) Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D40284 --- .../cmd/dtrace/test/tst/amd64/kinst/tst.basic.ksh | 1 + sys/cddl/dev/kinst/amd64/kinst_isa.c | 6 +++--- sys/cddl/dev/kinst/kinst.c | 21 +++++++++++++++++++++ sys/cddl/dev/kinst/kinst.h | 1 + 4 files changed, 26 insertions(+), 3 deletions(-) diff --git a/cddl/contrib/opensolaris/cmd/dtrace/test/tst/amd64/kinst/tst.basic.ksh b/cddl/contrib/opensolaris/cmd/dtrace/test/tst/amd64/kinst/tst.basic.ksh index e3585ca70793..3005da74c895 100644 --- a/cddl/contrib/opensolaris/cmd/dtrace/test/tst/amd64/kinst/tst.basic.ksh +++ b/cddl/contrib/opensolaris/cmd/dtrace/test/tst/amd64/kinst/tst.basic.ksh @@ -21,6 +21,7 @@ kinst::vm_fault: {} kinst::amd64_syscall: {} kinst::exit1: {} kinst::spinlock_enter: {} +kinst::memcpy: {} tick-10s {exit(0);} __EOF__ diff --git a/sys/cddl/dev/kinst/amd64/kinst_isa.c b/sys/cddl/dev/kinst/amd64/kinst_isa.c index 7aba79c1d481..d29f1cd4181f 100644 --- a/sys/cddl/dev/kinst/amd64/kinst_isa.c +++ b/sys/cddl/dev/kinst/amd64/kinst_isa.c @@ -107,10 +107,10 @@ kinst_trampoline_populate(struct kinst_probe *kp, uint8_t *tramp) ilen = kp->kp_md.tinstlen; - memcpy(tramp, kp->kp_md.template, ilen); + kinst_memcpy(tramp, kp->kp_md.template, ilen); if ((kp->kp_md.flags & KINST_F_RIPREL) != 0) { disp = kinst_riprel_disp(kp, tramp); - memcpy(&tramp[kp->kp_md.dispoff], &disp, sizeof(uint32_t)); + kinst_memcpy(&tramp[kp->kp_md.dispoff], &disp, sizeof(uint32_t)); } /* @@ -126,7 +126,7 @@ kinst_trampoline_populate(struct kinst_probe *kp, uint8_t *tramp) tramp[ilen + 4] = 0x00; tramp[ilen + 5] = 0x00; instr = kp->kp_patchpoint + kp->kp_md.instlen; - memcpy(&tramp[ilen + 6], &instr, sizeof(uintptr_t)); + kinst_memcpy(&tramp[ilen + 6], &instr, sizeof(uintptr_t)); } int diff --git a/sys/cddl/dev/kinst/kinst.c b/sys/cddl/dev/kinst/kinst.c index 46b9bf2f41e8..e30b813e0400 100644 --- a/sys/cddl/dev/kinst/kinst.c +++ b/sys/cddl/dev/kinst/kinst.c @@ -65,6 +65,27 @@ static dtrace_provider_id_t kinst_id; struct kinst_probe_list *kinst_probetab; static struct cdev *kinst_cdev; +/* + * Tracing memcpy() will crash the kernel when kinst tries to trace an instance + * of the memcpy() calls in kinst_invop(). To fix this, we can use + * kinst_memcpy() in those cases, with its arguments marked as 'volatile' to + * "outsmart" the compiler and avoid having it replaced by a regular memcpy(). + */ +volatile void * +kinst_memcpy(volatile void *dst, volatile const void *src, size_t len) +{ + volatile const unsigned char *src0; + volatile unsigned char *dst0; + + src0 = src; + dst0 = dst; + + while (len--) + *dst0++ = *src0++; + + return (dst); +} + int kinst_excluded(const char *name) { diff --git a/sys/cddl/dev/kinst/kinst.h b/sys/cddl/dev/kinst/kinst.h index ee756dc87d09..1107a274333f 100644 --- a/sys/cddl/dev/kinst/kinst.h +++ b/sys/cddl/dev/kinst/kinst.h @@ -46,6 +46,7 @@ extern struct kinst_probe_list *kinst_probetab; struct linker_file; struct linker_symval; +volatile void *kinst_memcpy(volatile void *, volatile const void *, size_t); int kinst_excluded(const char *); int kinst_md_excluded(const char *); int kinst_invop(uintptr_t, struct trapframe *, uintptr_t);
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