From 61a32cf95e9712e8d84e85c9cc0f057376009bd2 Mon Sep 17 00:00:00 2001
From: Tobias Frost <tobias.frost@bshg.com>
Date: Wed, 22 Jun 2022 12:58:56 +0200
Subject: [PATCH] Consider page size in report_mmap / report_unmap.

mmaps are full of quirks ;-)

- mmap(2) will always allocate whole memory pages, even if the
  caller only reuqests a partial page.
  This is considered by calculating the "real" size of the mmap.

- munmap(2) also operates on pages, unmapping every page it "touches.",
  so the size parameter is adjusted if needed.
---
 report.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/report.c b/report.c
index cf3be27..6306b37 100644
--- a/report.c
+++ b/report.c
@@ -241,6 +241,9 @@ static void _report_calloc(struct task *task, struct library_symbol *libsym)
 	report_alloc(task, MT_MALLOC, ret, size, options.bt_depth, libsym);
 }
 
+
+static ssize_t arch_pagesize = -1;
+
 static void _report_mmap(struct task *task, struct library_symbol *libsym)
 {
 	unsigned long ret = fetch_retval(task);
@@ -249,6 +252,11 @@ static void _report_mmap(struct task *task, struct library_symbol *libsym)
 		return;
 
 	unsigned long size = fetch_param(task, 1);
+	if (unlikely(arch_pagesize==-1)) arch_pagesize=getpagesize();
+	// fixup size, if size is not a multiple of the pagesize, we get the "partial" page too. -
+	if (size % arch_pagesize) {
+		size += arch_pagesize - size % arch_pagesize;
+	}
 
 	report_alloc(task, MT_MMAP, ret, size, options.bt_depth, libsym);
 }
@@ -277,6 +285,12 @@ static void _report_mmap64(struct task *task, struct library_symbol *libsym)
 	else
 		size.l = fetch_param(task, 1);
 
+	if (unlikely(arch_pagesize == -1)) arch_pagesize=getpagesize();
+	// fixup size, if size is not a multiple of the pagesize, we get the "partial" page too. -
+	if (size.l % arch_pagesize) {
+		size.l += arch_pagesize - size.l % arch_pagesize;
+	}
+
 	report_alloc(task, MT_MMAP64, ret, size.l, options.bt_depth, libsym);
 }
 
@@ -284,6 +298,12 @@ static void report_munmap(struct task *task, struct library_symbol *libsym)
 {
 	unsigned long addr = fetch_param(task, 0);
 	unsigned long size = fetch_param(task, 1);
+	if (unlikely(arch_pagesize==-1)) arch_pagesize=getpagesize();
+
+	// fixup size, if needed: all pages in [addr, addr+size] are unmapped -- see munmap(2)
+	if (size % arch_pagesize) {
+		size += arch_pagesize - size % arch_pagesize;
+	}
 
 	report_alloc(task, MT_MUNMAP, addr, size, 0, libsym);
 }