f4b7efe504
From busybox git. Devmem used to always map 2 pages in case the access would cross a page boundary, which fails if you try to access the highest page. Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
77 lines
2.4 KiB
Diff
77 lines
2.4 KiB
Diff
From 351ef7188a1a2e2f154bbda6f703c2d3f4af6d79 Mon Sep 17 00:00:00 2001
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From: Denys Vlasenko <vda.linux@googlemail.com>
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Date: Wed, 14 Apr 2010 13:37:25 -0700
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Subject: [PATCH] devmem: map two pages only if it is necessary
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function old new delta
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devmem_main 463 469 +6
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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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---
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miscutils/devmem.c | 21 ++++++++++++++-------
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1 files changed, 14 insertions(+), 7 deletions(-)
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diff --git a/miscutils/devmem.c b/miscutils/devmem.c
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index e13dedc..39b5808 100644
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--- a/miscutils/devmem.c
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+++ b/miscutils/devmem.c
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@@ -13,9 +13,9 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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uint64_t read_result;
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uint64_t writeval = writeval; /* for compiler */
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off_t target;
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- unsigned page_size = getpagesize();
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+ unsigned page_size, mapped_size, offset_in_page;
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int fd;
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- int width = 8 * sizeof(int);
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+ unsigned width = 8 * sizeof(int);
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/* devmem ADDRESS [WIDTH [VALUE]] */
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// TODO: options?
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@@ -50,15 +50,22 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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if (argv[3])
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writeval = bb_strtoull(argv[3], NULL, 0);
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} else { /* argv[2] == NULL */
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- /* make argv[3] to be a valid thing to use */
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+ /* make argv[3] to be a valid thing to fetch */
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argv--;
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}
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if (errno)
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- bb_show_usage(); /* bb_strtouXX failed */
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+ bb_show_usage(); /* one of bb_strtouXX failed */
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fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
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+ mapped_size = page_size = getpagesize();
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+ offset_in_page = (unsigned)target & (page_size - 1);
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+ if (offset_in_page + width > page_size) {
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+ /* This access spans pages.
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+ * Must map two pages to make it possible: */
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+ mapped_size *= 2;
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+ }
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map_base = mmap(NULL,
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- page_size * 2 /* in case value spans page */,
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+ mapped_size,
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argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
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MAP_SHARED,
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fd,
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@@ -68,7 +75,7 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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// printf("Memory mapped at address %p.\n", map_base);
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- virt_addr = (char*)map_base + (target & (page_size - 1));
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+ virt_addr = (char*)map_base + offset_in_page;
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if (!argv[3]) {
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switch (width) {
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@@ -119,7 +126,7 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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}
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if (ENABLE_FEATURE_CLEAN_UP) {
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- if (munmap(map_base, page_size * 2) == -1)
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+ if (munmap(map_base, mapped_size) == -1)
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bb_perror_msg_and_die("munmap");
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close(fd);
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}
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--
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1.7.1
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