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x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: EBC131C001D X-Stat-Signature: 3duughen3gtsfrb56di9gb1agrycsg9w X-Rspam-User: X-HE-Tag: 1728924395-668809 X-HE-Meta: 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 /xM2wFGf on8rwNYcejhRB2D60aP3Shk2za70QAfKApdGMBdc5/YQ7mATYQqPZf+gqBz0GOCe9oyFuU992FtI1uBXRFF6f7xqufYmaNsjG53vFkBv+/SIQZUUClptqmKD8Me+EA+kBxbd+qoCwiVGiXbox9ptezgae+X8okDzNuSp1MtqrihlM5xjoOc6WE1e1F+FnFBx9seJDG6IyywjzKyiWVbNYoE+62X2LJJKi7ZYAHP3yyQVCZ8LyOKt8nEU+kIFkbb8MA4/k9YlPutDRBGhXHqP8Htl0fbG4nqXOyvQlAgPI2CAMZSGsjhYS49+1X56eC3gRzUYBWMgJtJgVoN5jReaungCFMxdNIfP+zhFn5XZTGSB5JPy109op1OUnH82k5iNPdRNN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 14 Oct 2024 11:58:25 +0100 Ryan Roberts wrote: > To prepare for supporting boot-time page size selection, refactor code > to remove assumptions about PAGE_SIZE being compile-time constant. Code > intended to be equivalent when compile-time page size is active. > > Convert BUILD_BUG_ON() BUG_ON() since the argument depends on PAGE_SIZE > and its not trivial to test against a page size limit. > > Redefine FTRACE_KSTACK_ENTRIES so that "struct ftrace_stacks" is always > sized at 32K for 64-bit and 16K for 32-bit. It was previously defined in > terms of PAGE_SIZE (and worked out at the quoted sizes for a 4K page > size). But for 64K pages, the size expanded to 512K. Given the ftrace > stacks should be invariant to page size, this seemed like a waste. As a > side effect, it removes the PAGE_SIZE compile-time constant assumption > from this code. > > Signed-off-by: Ryan Roberts > --- > > ***NOTE*** > Any confused maintainers may want to read the cover note here for context: > https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/ > > kernel/trace/fgraph.c | 2 +- > kernel/trace/trace.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c > index d7d4fb403f6f0..47aa5c8d8090e 100644 > --- a/kernel/trace/fgraph.c > +++ b/kernel/trace/fgraph.c > @@ -534,7 +534,7 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, > if (!current->ret_stack) > return -EBUSY; > > - BUILD_BUG_ON(SHADOW_STACK_SIZE % sizeof(long)); > + BUG_ON(SHADOW_STACK_SIZE % sizeof(long)); Absolutely not! BUG_ON() is in no way a substitution of any BUILD_BUG_ON(). BUILD_BUG_ON() is a non intrusive way to see if something isn't lined up correctly, and can fix it before you execute any code. BUG_ON() is the most intrusive way to say something is wrong and you crash the system. Not to mention, when function graph tracing is enabled, this gets triggered for *every* function call! So I do not want any runtime test done. Every nanosecond counts in this code path. If anything, this needs to be moved to initialization and checked once, if it fails, gives a WARN_ON() and disables function graph tracing. -- Steve > > /* Set val to "reserved" with the delta to the new fgraph frame */ > val = (FGRAPH_TYPE_RESERVED << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET; > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index c3b2c7dfadef1..0f2ec3d30579f 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -2887,7 +2887,7 @@ trace_function(struct trace_array *tr, unsigned long ip, unsigned long > /* Allow 4 levels of nesting: normal, softirq, irq, NMI */ > #define FTRACE_KSTACK_NESTING 4 > > -#define FTRACE_KSTACK_ENTRIES (PAGE_SIZE / FTRACE_KSTACK_NESTING) > +#define FTRACE_KSTACK_ENTRIES (SZ_4K / FTRACE_KSTACK_NESTING) > > struct ftrace_stack { > unsigned long calls[FTRACE_KSTACK_ENTRIES];